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Investigations concerning the thermal alteration of silica minerals

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Title:
Investigations concerning the thermal alteration of silica minerals an archaeological approach
Creator:
Purdy, Barbara A
Publication Date:
Copyright Date:
1971
Language:
English
Physical Description:
x, 97 leaves : ill., part col. ; 28 cm.

Subjects

Subjects / Keywords:
Crystals ( jstor )
Flint ( jstor )
Heating ( jstor )
Ions ( jstor )
Ovens ( jstor )
Quartz ( jstor )
Specimens ( jstor )
Stone ( jstor )
Vitreous materials ( jstor )
Weight loss ( jstor )
Anthropology thesis Ph. D ( lcsh )
Dissertations, Academic -- Anthropology -- UF ( lcsh )
Flint ( lcsh )
Rocks, Siliceous ( lcsh )
Thermal analysis ( lcsh )
City of Ocala ( local )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Thesis - University of Florida.
Bibliography:
Bibliography: leaves 92-95.
Additional Physical Form:
Also available on World Wide Web
General Note:
Manuscript copy.
General Note:
Vita.

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University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Barbara A. Purdy. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
000559156 ( AlephBibNum )
13440713 ( OCLC )
ACY4604 ( NOTIS )

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Investigations Concerning the Thermal Alteration of Silica Minerals: An Archaeological Approach












By

BARBARA ANN PURDY


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF THE REqUIRENENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY





UNIVERSITY OF FLORIDA 1971




























PLEASE NOTE:

Some Pages have indistinct print. Filmed as received. UNIVERSITY MICROFILMS











ACKNOWLEDGMENTS


This study could not have been undertaken or successfully completed without the cooperation of many people with varying scientific backgrounds who contributed their knowledge, time, and equipment. This type of interdisciplinary approach is increasingly important as specialization becomes a necessity in an extremely complex world.

The author wishes to express appreciation to the

Department of Metallurgy for making it possible to use the Scanning Electron Microscope; the Civil Engineering Department for the use of their equipment and for assisting with the rock mechanics tests; the Soils Department for the use of their ovens, for assisting with differential thermal analysis, and for conducting the atomic spectrophometer analysis; the Geology Department for assisting with petrographic analysis, determination of surface area and porosity of Florida charts, and for permitting extended use of their oven; the members of my Supervisory Committee, especially Dr. Charles H. Fairbanks, for suggesting and approving of these investigations and for editorial assistance.

There are always special people without whose support graduate students might find completion of research projects overwhelming or impossible. This author is very grateful to: Mr. Don Crabtree of Kimberley, Idaholwhose ii






observance of the phenomenon of thermal alteration stimulated the undertaking of this study. During the summer of 1969, I attended a four-week Flintworking Session conducted by Mr. Crabtree at Shoshone Falls, Idaho. This session was sponsored by Idaho State University with funds granted by the National Science Foundation. Mr. Crabtree's encouragement and suggestions through personal conversations at that time as well as subsequent written communications have been invaluable. Dr. F. W. Zettler of the Plant Pathology Department at the University of Floridawho gave so generously of his time in helping me with the photographs, but whose real contribution was his enthusiasm which is more infectious than he realizes. Dr. H. K. Brooks of the Geology Department without whose help this project could not have proceeded beyond an idea. No phase of this study was undertaken or completed without his physical and mental participation.

Lastly, I would like to thank the members of my family for their patience since 1964.


iii











TABLE OF CONTENTS


ACKNOWLEDGEMENTS . . . . . . . . . .


LIST OF TABLES . . . . . .


LIST OF FIGURES . . . . . . . . . . . . .


ABSTRACT . . . . * . . . . . .


INTRODUCTION . . . . . . . . . . . . . . .

LITERATURE REVIEW . . . . . . . . . . . . . .


Exposure of Flint to Fire as an Aid i
Chipping Process . .
Use of Fire in Quarrying Operations .
Caches . . . . . . . . . . . . . .
Discussion . . . . . . .

MATERIALS .* . * * * . *. . . .

METHODOLOGY * . e. . . .* *


* . . . 1
* � 0 0 5


n the
* 0 o oS o o0


* 0 � * * * *

* � 0 S S 5 0


Heating Experiments . . . . . .
Weight Loss . . . . .
Decrepitation and Explosion Vitreousness . . . . . . .
Discussion . . . . . . . Iron Content of Florida Chert .


* 0 *
* . S
* 0 S
* S *
* 0 5
* S 0


Strength Tests . . . . . .***
Preparation of the Samples . . . .
Compressive Tests . . . . . . . .
Point Tensile Tests . . . . . .
X-Ray Diffraction Pattern . . . .
Differential Thermal Analysis (DTA) .
Petrographic Analysis. . . 0 . a .
Determination of Specific Surface Area Scanning Electron Microscope . . . . a

ARCHAEOLOGICAL APPLICATION . . . . . .

SUMMARY AND INTERPRETATION . . . . . .

BIBLIOGRAPHY . . . . . . . . . . . . .

BIOGRAPHICAL SKETCH . . . . . . . . . .


* 0 0 � 0 0

* � 0 0 0 5

* 0 0 S 0 0


. . & 0


. . . . . 0 * * V


. . . . . . viii












LIST OF TABLES


1. Heating Experiment to Determine Weight Loss of
1-Inch Cubes . . . . . . . . . . . . . . . . . . . 25

2. Heating Experiment to Determine Weight Loss of
Samples from Different Locations . . . . . . . . . 27

3. Results of Experiment Conducted to Determine Ability of Heated Rock Samples to Take On
Moisture . . . . . . . . . . . . . . . . . . . . . 30

4. Heating Experiment Conducted to Determine
Differences in Heated and Unheated Specimens
After Soaking for One Month . . . . . . . . . . . 32

5. Heating Experiment Conducted to Determine Weight
Loss of Archaeological Specimens Suspected of
Having Been Thermally Altered . . . . . . . . . . 33

6. Heat Soaking Experiment Conducted to Ascertain
Length of Time Necessary to Effect Thermal
Alteration . . . . . . . . . 0 0 0 0 0 0 * 0 0 . 0 42

7. Results of Atomic Absorption Spectrophotometer Analysis . 0 0 0 0 0 * 0 0 0 0 0 0 0 0 41 0 0 0 0 * 53

8. Results of Compressive Strength Tests When
Heated Specimens Are Subjected to a Cool
Environment While Still Hot . . . . . . . . . . . 63

9. Results of Compressive Strength Tests When Heated Specimens Are Allowed to Cool in the Oven 63

10. Results of Point Tensile Strength Tests ?0,











LIST OF FIGURES


1. Areal Distribution of' Outcrops Probably Containing Chert in Peninsular Florida . . . . . . . . . . . . 21

2. Weight Loss upon Heating of Cherts from Various Locations in Florida .*.* ee*. &a. * . 28

3. Weight Loss of Samples of Florida Chert Illustrating the Typical Pattern Observed for All Florida
Specimens Tested Throughout a Two-Year Period .29
4I. Explosion Resulting from Too Rapid Exposure to Heat . 36

5. Results of Experiment Conducted to Test the Validity of "Flaking"t Hot Stones by Dripping Cold Water
on Them . 0 . 0 * . * * . . . . . * . . * * . * * * 39

6. Vitreousness Occurring when Florida Cherts Are Heated and Subsequently Flaked . . . . . . . . . . 44

7. Example of a Potlid Fracture which Often Occurred when Florida Cherts Were Subjected too Rapidly
to 400*C Temperatures. . 0 * ** . . . * 54

8. Examples of a "Crenated" Fracture which Often Occurred when Specimens Were Removed Directly from
a Hot Oven to aCool Environment . * *.0 0. 55

9. Specimen Depicting Intentional Fracture with Bulb of Percussion and Typical Fractured Surface
Emphasizing that Impact Has Occurred . . . . . . . 56

10. Heated Specimens and Unheated Controls Illustrating
Degree of Color Change Depending upon the Amount
of Iron Present inthe Chert . . . . . . . . 58

11. Composite Illustration of: (a) Drill Press,
(b) Corematic Diamond Core Bit, and (c) a Chert
Nodule with Cores Removed to 'Be Used for
Strength Tests . . . . . . 0 4. 0 . 0 & 0 & . 61

12. Decrease or Increase in Compressive Strength over
Unheated Controls of Heated Specimens . * * * * * * 64

13. Composite Illustration of: (a) Compressive Strength
Testing Machine, (b) Close Up of Jig with Core in
Position, and (c) Core Split by Application of
Point Tensile Load . . . . . . 0 0 . & 0 0 0 . 0 * . 67






14. X-Ray Diffraction Pattern Illustrating that No
Change Occurs in the Crystal Lattioe when Florida
Cherts Are Subjected to Critical Temperatures . . . 72

15. Results of Differential Thermal Analysis . . . . . . 74

16. Petrographic Sections Showing No Detectable Change
in Heated vs Unheated Florida Chert . . . . . . . . 77
17. Surface Topographyr of Unheated and Heated Johnson
Lake Chert Samples as Viewed by the Scanning
Electron icosco. . . . . . . . . 80

18. Surface Topography of Unheated and Heated Silicified
Coral from Florida as Viewed by the Scanning
Electron M~icroscope . . . . . . . . . . . . . 0 0 . 81

19. Specimens from the University of Florida Collections
Showing Dull Areas Not Flaked Subsequent to Thermal
Alteration Surrounded by Extreme Vitreousness in
Areas that Have Been Flaked after Alteration . . . 86


Vii






Abstract of Dissertation Presented to the Graduate Council of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

INVESTIGATIONS CONCERNING THE THERMAL ALTERATION
OF SILICA MINERALS: AN ARCHAEOLOGICAL APPROACH

By

Barbara Ann Purdy

March, 1971

Chairman: Charles H. Fairbanks Major Department: Anthropology

A recent publication (Crabtree and Butler 1964)

suggests that prehistoric man may have found it advantageous to thermally alter lithic raw materials prior to manufacture or final completion of chipped stone implements.

The specific objectives of this research and the conclusions reached are as follows:

1. To establish whether a functionally desirable change in chert occurs when it is subjected to heat. Experiments were conducted to determine the temperature and length of time necessary to effect the detectable physical alterations. Heated and unheated Florida charts were studied by petrographic analysis, x-ray diffraction, differential thermal analysis, scanning electron microscope, atomic spectrophometer analysis, standard rock mechanics test, and the gas absorption surface area and porosity technique.

2. To determine whether primitive peoples might have been aware of the advantages conferred by thermally altering lithic materials. A review of the literature revealed no completely adequate account describing this technique. Enough records exist, however to warrant the viii






conclusion that fire was used sometimes in conjunction with lithic technology.

An examination of archaeological chipping debris

revealed that a portion of this debitage had been intentionally flaked after heating. The flaked surfaces are lustrous and differ in this respect from outcrop samples of the same materials. The flakes also have bulbs of percussion indicating that impact has taken place. Bulbs of percussion are not present when rocks explode from thermal stresses though the conchoidal fracture typical of flint materials is evident.

3. To recommend a technique which might be employed by archaeologists to determine whether the chipped stone remains recovered from sites had been thermally altered. No practical standardized test was discovered. However, from an examination of a representative sample of flaking debris, an investigator should find a number of specimens exhibiting a relict dull area surrounded by areas of high luster. This situation strongly suggests that the dull area has not been flaked subsequent to heating, whereas the vitreous area has been flaked.

Temperatures of 350*C-400*C are sufficient to alter Florida cherts but x-ray diffraction patterns demonstrated that no change in the crystal lattice occurs. This was borne out by petrographic analysis which showed no change in the shape, size, or orientation of the microcrystals. The alteration is due, at these low temperatures, to the presence of impurities in the rock serving as fluxes to ix






firmly cement the microcrystals of quartz. This fusion led to approximately a 45% reduction in strength necessary to fracture Florida charts under point tensile load, and approximately a 60% reduction in the intergranular surface area. When the rock is fractured subsequent to thermal alteration, the fractured surface is extremely vitreous. The fracture splits the grains, rather than breaking around them as in unheated counterparts, revealing the true luster of quartz. Since crystal boundaries are no longer interfering with the removal of flakes, heated material fractures more like glass than like a rock aggregate. This fact is dramatically illustrated by the change in surface topography when viewed by the scanning electron microscope. A color change may occur when charts are heated if iron is present in sufficient quantities. Color change occurs at a lower temperature than that effecting thermal alteration but may be used as a valid criterion if accompanied by vitreousness.

The information gained from this study leads to the conclusion that if flint materials are cautiously heated for sustained periods, an alteration occurs which confers an advantage in manufacturing chipped stone implements. Furthermore, prehistoric peoples were probably well aware of this advantage.












INTRODUCTION


A recent publication (Crabtree and Butler 1964)

suggested that prehistoric man may have found it advantageous to thermally alter his lithic raw materials prior to manufacture or final completion of chipped stone implements. Subsequent examination of chipped stone tools as well as of waste flakes recovered from archaeological sites led to the speculation that this technique had been employed aboriginally in the state of Florida. Florida materials often exhibit the pinkish cast and vitreous luster felt to be indicative of thermal alteration and differ markedly from the siliceous materials found in outcrops.

Since the summer of 1968, the author has studied

the collections of stone tools in the Florida State Museum. Specimens from every Florida county are represented but samples are scarce from counties where there are no natural outcrops of chert, e.g., south Florida. Waste flakes were not available since they had been discarded. For several years, however, the Department of Anthropology at the University of Florida has been storing all stone materials recovered, including chipping debris. This debitage was also examined. This extensive search has led to the deduction that the original speculation was valid, i.e., many of the chipped stone remains appear to have been thermally
1





2
altered. The number might be greatly increased if it were known whether patinated specimens or specimens recovered from under the water had been subjected to heat. Patination as well as minerals present in Florida lakes, rivers, and springs cause changes which conceal the original texture of chert, making it impossible to determine (at present) if thermal alteration has taken place.

The objectives of the research then undertaken were:

1. To establish whether a functionally desirable change in the chert occurs when it is thermally altered. The experiments conducted are described in the section on Methodology which embodies the major portion of this dissertation.

2. To demonstrate whether prehistoric peoples might have been aware of the advantages conferred by thermally altering their lithic materials. To aid in this endeavor, an intensive and extensive search of existing publications was undertaken. The results of this search are described in the Literature Review.

The use of analogy in interpreting archaeological

data "In its most general sense . . . is assaying any belief about nonobserved behavior by referral to observed behavior which is thought to be relevant" (Ascher 1961: 317). Unfortunately, historic accounts were not found which accurately described the process of thermal alteration. However, enough descriptions of the use of fire during some stage of stone tool manufacture were uncovered to warrant the conclusion





3
that the "observed behavior" would have been "relevant" to the problem being investigated if the observers had paid more attention to detail and had provided a more thorough description.

In addition, in the section on Methodology, comparisons are made between materials that have been intentionally subjected to heat under controlled conditions and subsequently flaked with samples exhibiting potlid fractures where heat has been applied suddenly, e.g., through forest fires. Other types of fracture resulting from expansion and contraction are noted. This analysis served as a reminder that flint materials may break with a conchoidal fracture but that no bulb of percussion will be present unless impact .has taken place. The archaeological debitage suspected of being intentionally heated does possess bulbs of percussion. "Solutions to any problem are at best approximations arrived at by the elimination of those least likely" (Ascher 1961: 323). In this case, archaeological remains have provided clues to prehistoric practices through systematic elimination of alternative solutions.

The hypothesis that heat was used by aboriginal

peoples to alter lithic raw materials prior to final manufacture of chipped stone tools is strengthened by (1) historic accounts, (2) experimentation with and study of intentional vs unintentional fractured surfaces, (3) comparisons between outcrop and site materials, (4) heating experiments with outcrop materials resulting in specimens whose appearance





4~
resembles artifactual remains, and (5) tests demonstrating that thermally altered siliceous materials are easier to flake.

3. To suggest a technique which might be employed by archaeologists to determine if the chipped stone remains recovered from archaeological sites had been thermally altered. This presupposes that the alteration is a permanent one readily ascertained by subjecting the material to some sort of standard test. This problem is discussed in the section on Archaeological Application.












LITERATURE REVIEW


Following Crabtree and Butler's (1964) article,

archaeologists began to look for indications of alteration by heat of materials used in making chipped stone implements. It now appears that this phenomenon is very widespread. Despite the fact that most early explorers, colonists, traders, missionaries, and adventurers were very poor ethnologists, it seemed surprising that this technique had not been observed and described. American Indians, as well as other primitive peoples around the world, readily perceived the advantages of iron tools which were introduced to them through European contact. They willingly put aside nearly two million years of stoneworking technology, often within a single generation. Unfortunately, very little attention was devoted to the material or practical aspects of Indian life until the middle of the nineteenth century. It wasn't until many aboriginal practices had been discontinued that a rapid attempt to record these practices was undertaken. In some cases, this attempt came too late. For obvious reasons, therefore, it was necessary to turn to nineteenth century sources almost entirely. Thus, literature, which in most fields of endeavor has been laid to rest, was reviewed in an attempt to shed some light on a recent observation of man's past behavioral patterns.

5





6
Many excellent accounts exist of aboriginal stoneworking techniques. In addition, numerous experimental studies have been conducted and reported upon which describe the step by step manufacture of tools by direct percussion, indirect percussion, pressure, and various combinations of these methods. These techniques constituted the major processes employed in shaping and finishing stone tools. The author does not wish to give the impression that it was always necessary to thermally alter lithic materials. Some materials probably needed no alteration. Nor is it felt that fire was used in shaping. But it is thought that fire often played an important role in making the mechanical processes less difficult during some stage of manufacture prior to final retouch.

Holmes (1919) compiled a summary volume entitled

Aboriginal American Antiquities, the sources for which are nearly all pre-twentieth century as a perusal of the bibliography indicates. This book served as a springboard to the past since Chapter XXXV is entitled "Fire Fracture Process" and contains a number of useful references; those of which were available, in turn, led to others. Many of these early publications were not available. Despite the fact that complete coverage was not possible, it soon became apparent that man's use of fire in connection with his chipped stone tool-making technology fell into three main categories:

(1) exposure of flint to fire as an aid in the chipping process, (2) use of fire in quarrying operations, (3) caches.






Exposure of Flint to Fire as an
Aid in the Chipping Process

This category deals primarily with firsthand accounts or, perhaps more accurately, fanciful interpretations of firsthand accounts.

It seems appropriate to mention the following wellknown description which appears to have had its genesis with Herman Lehmann:

We threw a large flint stone, from two to six
feet in circumference, into the fire. After the
stone became very hot, small thin pieces would pop
off; we selected those pieces which would require the least work to put into shape, and picked these
pieces up with a stick split at the end; while these pieces were very hot, we dropped cold water on those places we wished to thin down; the cold water caused the spot touched to chip off, and in this way we made some of the keenest pointed and sharpest arrows that could be fashioned out of stone (Wallace and Hoebel
1952: 105).
Though widely accepted by laymen, the famgoing has been largely discredited by most professionals. To those who are sophisticated in the art of flintknapping, it does seem like a waste of time to use this method even if one could control the dripping of water sufficiently to predict the type of flake that would be removed; the work would proceed much faster by using a percussor or pressure tool.

A-long this same line, Holmes (1919: 364) cites "A

remarkable account of the use of fire in chipping flint implements . . . furnished by Thomas H. Fraser" who

was informed by Chief Paul, the head of a remnant
of the Mic-mac tribe, resident on the northern coast of Nova Scotia, that in his grandfather's time, flint
arrow-heads were made by the systematic application of
fire and water, and I still have in my possession an
arrow-head made according to the process described by
him.







Holmes (1919: 364-5) quotes accounts of the Digger

Indians on the eastern side of the Sacramento River and of

the Seri Indians of western Sonora, Mexico, who employed

essentially the same technique. It would appear that these

methods were not actually observed by the recorders.

Ellis (1940a; 42) furnishes other accounts pertaining

to the Athabascan use of this method and describes several

experiments where "chipping" in this way was attempted in

order to settle the question as to whether dripping water

to remove flakes is fact or myth.1 He says:

Experimental attempts to duplicate this fracturing
technique have shown it to be very unsatisfactory. In
the first place flint exposed to an open flame for even
a short length of time will heat through and shatter into angular fragments and tiny flakes. The portions of the flint which do not shatter may be treated with cold water dropped from the end of a stick or by other
means with little reaction. The usual result of the
application of cold water to hot flint is the boiling
and rapid evaporation of the drops of water. Occasionally small chips may fly off, but their direction and
position cannot be controlled. Dropping thoroughly
heated flint into a pan of cold water will simply remove tiny fragments which are broken away by the sudden
change in temperature, but often even this treatment has negative results. Also the flint which has been subjected to fire is so filled with tiny fire cracks and the surfaces of the material so roughened due to the differential expansion of the crystals caused by the heating, that it is impossible to use it to any
practical advantage in the shaping of stone implements.
An examination of thousands of specimens in the museum
failed to indicate that fire played any part in their
manufacture (Ellis 1940a: 43).

Pond's (1930: 25) account is in complete agreement

with Ellis.


lAn experiment was carried out which is described in the section on Methodology that was conducted prior to a knowledge of Ellis' work. The results were identical.





9
Schumacher reports that

The rock is first exposed to fire, and, after a
thorough heating, rapidly cooled off, when it flakes
readily into sherds of different sizes under well
directed blows at its cleavage (1877: 547).

Powers records the following:

It was a source of wonder to me how the delicate
arrow-heads used on war-arrows with their long thin
points could be made without breaking them to pieces.
The Viard EWiyotJ of northern California proceed in
the following manner: Taking a piece of jasper, chert,
obsidian, or common flint which breaks sharp-cornered
and with a conchoidal fracture, they heat it in the
fire and then cool it slowly, which splits it in
flakes (1877: 104).

Other authors (e.g., Mason 1887.:.226; Fowke 1896: 172) refer to the Powers and Schumacher accounts but add nothing pertinent. The methods described by Powers and Schumacher are more plausible than those avowing that arrowheads are made by dripping cold water on hot stones; however, it should be pointed out that they are in the minority.

The above references constitute the totality of the

available information on this subject with regard to American Indian practices unless some undiscovered source exists.

The author is in frequent correspondence with Kenneth P. Oakley of the British Museum, London. He was not aware of this technique at all and could not "recall reading any account of any people heating stone before finishing in projectile-point form" (Oakley 1970, personal communication). Another European scholar, Fran~ois Bordes

laughed until he tried heating some flint and
thenohe became convinced. He has now traced the
thermal treatment back to Solutrean [see Bordes 1968: 159] and both he and Tixier have done extensive work
on experimental heat treating (Crabtree 1969, personal
communication).






Thus, there appears to be even less information from European sources than from the New World. However, the following account concerning the Andaman Islanders demonstrates that the intentional heating of stone to cause alteration was not unknown to certain groups in the Old World. This is even the more interesting since the Andaman Islanders were reported to have no knowledge of how to kindle fire.

Chips and flakes are never used more than once;
in fact, several are generally employed in each
operation. . . . Flaking is regarded as one of the duties of women, and is usually performed by them.
For making chips two pieces of white quartz are
needed; the stones are not pressed against the thigh,
nor are they bound round tightly so as to increase
the line of least resistance to the blow of the flaker;
but one of the pieces is first heated and afterwards allowed to cool, it is then held firmly and struck at right angles with the other stone: by this means is
obtained in a few moments a number of fragments suitable for the purposes above mentioned . . . (Man 1883:
380).

A paraphrasing of this quotation is to be found in Mason (1895: 137)*


Use of Firein Quarrying Operations

The information contained in this category comes from archaeological excavations and observations made at quarry sites no longer in operation.

The most widely quoted use of fire in aboriginal quarry sites is that of Fowke in his description of Flint Ridge, Ohio:

Traces of fire were plainly visible in the
its, from which the inference is natural that fires
were built upon the rock, and that, while heated, water was thrown on it. The stone could thus be
broken into pieces (Wilbm 18917: 870).






Holmes (1919: 176-7) quotes Fowke in a similar

description of the use of fire discovered in another pit

at Flint Ridge, then adds

In general, however, the action of fire is destructive to stone, and if not very discreetly employed will so flaw the stone as to make it unfit for most uses. Fowke tells us how this destructive tendency
was probably avoided by the ancient quarrymen of Flint Ridge. According to his determination, fire was built
upon the surface of the flint body, such portions of
the purer stone as were desired for use being protected
from the action of the heat by layers of moist clay
(Holmes 1919: 364).

At the novaculite quarries near Hot Springs, Arkansas,

which are possibly as extensive as those of Flint Ridge, Ohio,

Holmes (1919: 198) observed some use of fire in the quarrying

operations.

Ellis (1940a: 45) describes an experiment conducted

by William G. Mills at Flint Ridge which may cast some doubt

on the use of fire in quarrying operations:

11 . . . here was the bed of flint uncovered and an
abundance of dry wood at hand. The fire was kindled, and was kept burning for two hours, producing an intense heat on the underlying surface of the flint.
The fire was then removed and two buckets of cold
water were thrown upon the surface. I fully expected
the flint to break in large pieces, but it merely
checked and cracked into small pieces to the depth of
perhaps half an inch. After the conclusion of this
experiment it was apparent that fire as a direct agent
in quarrying of flint was perhaps not effective."

The following account of Indian jasper mines in the

Lehigh Hills of Pennsylvania is interesting because it hints

at the possible use of fire to fracture stone in a manner

similar to the historic observances described in the previous

category:

Scattered fragments of charcoal were scarce in
shaft 12 below the ninth foot, but all the other
diggings and dumps were sprinkled thick with bits of





12
charcoal. About 20 per cent of the chips and 10 per cent of the large blocks were reddened as if by fire,
while reddened fragments were abundant in all the
fire-places. Nothing was surer than that fire had
played a great part in the quarrying process; but while
four fire-places examined showed no trace of cooking,
they also gave no sure clue to their purpose, and there
would have remained a doubt whether the fires had not
been built for warmth had not a fifth hearth discovered in shaft 2, at a depth of 15 feet, seemed to settle the question. It was an oven regularly built of blocks of jasper and contained a mass of charcoal
and ashes. The fact that the sides of the blocks were
reddened, and several had already split through the middle, while the interstices were filled with fine
splinters, offered conclusive evidence that the quarrymen had built the fire to fracture the blocks, which
measured 2 feet, 1-112 feet, 6 and 7 inches respectively in diameter.
My experiments proved (a) that if a large block
of two feet in diameter is thoroughly heated on a
wood fire it breaks into numerous pieces at a moderate
blow; (b) that only the fragments near the fire are reddened; (c) that the fragments lose their original
gloss by the process. The luster, however, seemed to
be regained by long burial in damp clay, as was indicated
by the high-polished fracture of some of the reddened chips found on the fire-places. Moreover, many of the worked forms gathered on the surface had been probably
fire-reddened, and it is not unlikely that the Indian
could have so heated the blocks as to reach their purer
parts without spoiling the whole, while many of the
large and coarse blocks might have been fire-fractured
to get them out of the way (Mercer 1894: 84-6).

Oakley (1969, personal communication) says "I have

come across evidence at several localities suggesting that

stone age craftsmen sometimes obtained flakes of intractable

stone by using the method of 'fire setting,' . . ." Also

At Hangklip on the coast east of the Cape Peninsula,
South Africa, erosion of peat has revealed a Late
Acheulian factory site. At the base of large blocks
of Table Mountain Sandstone protruding through the peat there are quantities of large thermal flakes,
and on the surrounding ancient ground surface there
are many broken or incomplete hand-axes and cleavers
made from such flakes. Professor A. J. H. Goodwin has
suggested that Acheulian man obtained the flakes by the method of 'fire-setting,' that is to say burning
fires around the blocks of sandstone and then dashing





13
water on to the heated rock to cause exfoliation.
However, as far as I am aware, no ashes have been
found around the blocks (Oakley 1955: 45).

This report is particularly interesting since it

suggests that at a very early time man had a sophisticated knowledge not only of stone fracturing processes but also of the use of fire.


Caches

For many years stone caches consisting of arrowheads, spearheads, grooved axes, polished stone hatchets, large chipped flints, spades, etc., have been reported in the literature and there has been much speculation concerning why these were deposited. It seems perfectly reasonable to suggest that a flint cache as described recently by Hammatt (1970: 141) was used as a paleo-Indian butchering kit. Other suggestions that have been encountered in the Literature are that the stones were (1) buried to keep them moist; (2) buried to hide them from enemies; (3) used as grave goods; (4) unfinished preforms to be completed later. It therefore is fair to add yet another suggestion: some 11caches" existed because the buried flints were being thermally altered in order to make final chipping easier. While only a small number of descriptions mention the presence of charcoal, it seems plausible to assume that a farmer plowing a field who uncovers as many as several hundred flint implements at one fell swoop is not going to stop to notice that the pit also contains evidence of fire. Therefore, the number of references might be multiplied many times if the excavations had been conducted in the mid-twentieth century.






Montgomery County, New York: . . . a cache of 117
arrowpoints on the farm of . . . near a spring.
They lay about 6 inches below the surface, on a bed
of ashes 3 inches thick, which rested on a hearth or
fireplace, about 10 feet square, of cobblestones from the drift. The arrowpoints average about 3 inches in
length and are of dark-blue and gray flint, leaf-shaped
(Wilson 1897: 971).

Old fort and village site in Saline County, Missouri: Three feet farther from the center was the edge of a
Pit 5 feet in depth and 6 feet in diameter. At one
point on the bottom was a pile of minute flint chips
scaled off in making implements of small size or
delicate finish; there were enough of these to fill a
pint cup. A slightly smaller quantity of similar chips
lay higher up (Fowke 1910: 90).

Duchess County, New York: While employed in digging,
his spade brought up a number of arrow-points. He
described them to be nicely piled side by side, edgewise, in two or three rows. There were perhaps two or
three hundred in all. On each side and on top were some charred logs and sticks, that seemed to be the
remains of an old fire. They were 10 or 15 inches below
the surface of the pond. They are of a blue jasper flint, and seem to be in an unfinished condition. I
thought that probably the Indians had brought them
from a distance (as I have never found any of the same
rock anywhere in this neighborhood) and made this
pocket and covered the traces of them by building a fire, intending to return and finish them at their
leisure; or, perhaps, they hid them there to prevent their capture by their enemies (Shepard 1877: 307-8).

In 1894, Dr. J. F. Snyder excavated Mound No. 1 of the
Baehr Group, on the west side of the Illinois River,
thirteen miles below Beardstown, and opposite the mouth
of Indian Creek [Illinois]: At the base of the mound
was an oval of clay on which "was a mass of black hornstone implements, that apparently had been thrown down
in lots of 6 to 20, with sand over and between each lott as though to isolate them from each other. This deposit
of 6,199 flints was covered with a stratum of clay, 10 inches in thickness; and on this a fire had been maintained for some time . . . . The flints forming
the nucleus of this mound are very . . . rudely fashioned;
some are quite neatly finished, but the greater part
of them are only chipped and ill-shaped. . 0 611 . . . they
do seem to be unused blanks (Ellis 1940b: 112).

It is interesting to note that most of these accounts

mention charcoal and the unfinished condition of the finds.





15
This is exactly what one would expect if these "caches" consisted of preforms to be thermally altered prior to final chipping. There would be no reason why they couldn't be left for extended periods until needed. Perhaps they were never recovered by their owners because European introduction of iron and/or disruption of the aboriginal way of life intervened.


Discussion

In addition to the references cited there are other accounts tantalizingly suggestive of thermal alteration of rocks used to make projectile points. It is tempting to interpret these descriptions as evidence of heat treating simply because it would be rewarding to discover an accurate account:4 however, they must be considered conjectural until proved otherwise. This might be accomplished by reexamining cache collections as well as conducting excavations with this problem specifically in mind.

It is possible that pertinent publications may have

been overlooked (many were not available), but it is unlikely that there exists anywhere in early documents the step by step procedure involved in thermally altering siliceous materials under controlled conditions. Several authors, most of whom have already been quoted, consistently mentioned the use of fire. A summary of this information might be as follows:,

These processes [of shaping] are distinguished by
such terms as breaking, flaking, . . . All are purely mechanical; none are chemical, save a possible use of
fire to induce changes in the rook in some parts of
the quarry work (Holmes 1893: 25).





16
It may be concluded, therefore, that Crabtree

made a significant and original contribution with his observation, experimentation, and description of this phenomenon,

I first discovered the thermal treatment when I
was about 17. 1 would find worked aboriginal material
of superb quality, but when I found the raw material
source it was never the same and had an entirely different texture. I finally wondered if they had in
some way treated the stone and so tried the old coal
range and heated the rocks which I buried in sand.
After much trial and error, I was able to duplicate
the texture of the worked pieces and decided this
was what they must have done. I could get no one to
accept the theory, however, until the Les Eyzies
conference in 1964. Tixier accepted it readily as
he had encountered the same complex problem in Algeria
(Crabtree 1969, personal communication).

Since 1964, many archaeologists throughout the New and Old Worlds are beginning to suspect that much of the stone remains recovered from archaeological sites has been subjected

to thermal treatment.

Since the Literature Review has revealed no accurate early description relative to this problem that might be applied to archaeological finds, at least a portion of the major contribution aimed at in this investigation seems to have failed, i.e., it should be possible to demonstrate that prehistoric peoples were aware of the advantages conferred by thermally altering their lithic materials. However, enough accounts exist describing the use of fire in some phase of the manufacture of flint tools that the evidence cannot be considered entirely negative. It is not surprising that accurate accounts do not exist when it is taken into consideration that;






1. Europeans who first encountered the American
aborigines were concerned with matters other
than stone technology, eog., survival in a new
ecological situation.

2. It was more fashionable to record esoteric ceremonial performances than the practical aspects
of native life.

3. Iron was almost immediately substituted for stone
in making implements; in fact even prehistorically
in the Southeastern United States, arrows and
spears were often headed by materials other than
stone: bird bones, bird bills, fish scales, fish
teeth, fish fins, animal bones, animal teeth,
horseshoe crab tails, and oyster shells. Some had
no separate head--the wood or cane of the arrow
shaft was merely sharpened and served as the point.

4,I. Since chipping stone tools (except for gun flints)
was not part of European technological knowledge at the time of contact, not enough was known to
observe or describe the procedure accuratelymuch
less interpret such an alien process.

5. Most explorers, adventurers, etc.,were not among
the Indians for extended periods. It is possible
that this procedure occurred only at special times
or in specific locations and was considered too
mundane to mention.,

To establish that desirable changes do occur when

siliceous materials are subjected to critical temperatures,

it was necessary, therefore, to turn to nonanthropological

literature. These publications will be cited in appropriate


places in the section on Methodology.











MATERIALS


The terms chert and flint have been used interchangeably and it is difficult to determine from the literature if any actual structural differences exist between them.

Flint is a term widely used both as a synonym for chert
and for a subvariety of that material. Tarr says that
flint is identical with chert in texture and composition and the term, therefore, should be dropped or reserved for artifacts (Pettijohn 1949: 320).

Thus, in describing chipped stone tools, one might say, for example, that flint artifacts were manufactured of Arkansas novaculite, Pennsylvania jasper, etc. This is, of course, already being done to a certain extent and to those interested inlithic technology information of this nature is important since it contributes greatly to an understanding of the kind of workmanship that might be expected or whether trade relationships existed if the material is not local.

N ost archaeologists would define flint as a rock composed of microcrystalline quartz that breaks with a conchoidal fracture. This is an adequate general description, but does not suffice when specific materials from diverse geographic areas are being considered. From the standpoint of this investigation, knowledge of the formation and composition of siliceous materials native to the state of Florida is necessary since alteration by heat might not take place at the same temperature in materials whose structure is slightly different.
18





19
Chert, being a rock, varies greatly in its physical characteristics even though the basic components, the minute crystals of quartz, are uniform in character. The factors that determine the physical properties of cherts are:

(1) the size of the quartz crystals; (2) how the anhedral crystals fit together affecting porosity and fracture;

(3) the amount of foreign material present, fossil replacements, and other heterogeneities including flux compounds;

(4i) void spaces; and (5) crystalline fabric (the crystals are not equidimensional or always randomly oriented). Thus, in the Florida cherts, there are different types and even a single nodule is not necessarily homogeneous throughout its mass.

The lithic raw materials used almost exclusively in this study were Florida cherts. Justifications for using a general term such as chert are as follows. To this author, at least, the term flint indicates an extremely fine-grained material found in the chalks of England. Also, as stated above, flint is used as a common designator for artifacts with no specific material intended. Using the modifier Florida preceding the word chert. calls to mind a particular type of material much as Arkansas novaculite, Pennsylvania jasper, or English flint does. Though there is a range of differing textures and homogeneities, Florida cherts were all formed under similar conditions and share common characteristics which distinguish them from other siliceous rocks.

There are a number of conditions under which chert

will form. Florida cherts occur as a secondary formation due





20
to the replacement of carbonates with silicas. All of the chert deposits in Florida are in relationship to relict clay hills in contact with limestone; these generally correspond to the Ocala Arch where siliceous deposits lie unconformably over the Ocala Limestone. Cherts also occur at the edge of the arch where limestones are interbedded with siliceous deposits. The occurrence of cherts is thus in the upper part of the Eocene Ocala Limestone, and the Oligocene and Lower Miocene Formations bordering the areas of the Ocala Uplift. Cherts found on the Ocala Arch have replaced limestones that are Eocene in age and those such as occur in Hernando and Hillsboro Counties have replaced limestones that are Oligocene and Lower Miocene in age. Cherts in the Miocene deposits are found as far south as Zulpho Springs, Hardee County. There are no cherts naturally outcropping along the east coast of Florida or in south Florida (Brooks, personal communication). Figure 1 shows the extent of the areal distribution of formations that might contain chert in peninsular Florida.




































L MI 0C EN E Li OLIGOCENIE []EOCENE


Figure l.--Areal Distribution of Outcrops Probably Containing Chert in Peninsular Florida (adapted from Cook 1945, Plate 1; Brooks, unpublished geologic map of Florida).











M~ETHODOLO0GY


The experiments described in this section were conducted primarily to determine whether some sort of alteration takes place in microcrystalline rock types upon heating that makes them easier to flake, especially to pressure flake. If such a change does occur, the author proposed to determine at what temperature alteration takes place and what are the physical or chemical changes that cause alteration.

Whenever comparisons are made between heated samples and unheated controls,, the specimens were obtained from the same core. An attempt was made to use material as free from fossil inclusions or other heterogeneities as possible and to obtain the samples from approximately the same area of the core since textural differences do occur; for instance, the area directly under the cortex is nearly always finer grained than further within the mass. Throughout this section reference is made to

1. Critical temperatures: this should be interpreted
as 3500C-4000C for Florida cherts.

2. Slow rise in temperature: the materials being
heated were subjected to 5000 elevations in
temperature until the testing temperature was
reached; they were left at each succeeding increment for a sustained period--usually 24 hours.

3. Rapid rise in temperature: the materials being
heated were subjected to 500C elevations in
temperature until the testing temperature was
reached; they were left at each succeeding increment for a short period--generally 1 hour.
22





23
Heating Experiments

All of the experiments involved the use of heated and unheated specimens but it was necessary to create a special category describing the many and varied conditions under which the rock materials were thermally treated. These tests followed what might be considered an evolutionary sequence since the results of one experiment often dictated the need for another which in turn suggested still others. As pointed out in the Literature Review, only Crabtree and Butler's (1964) article discusses heating of siliceous materials from an archaeologically significant point of view; therefore, these experiments are of a pioneering nature.


Weight Loss

Twelve 1-inch cubes, each weighing approximately 42 grams, were laboriously prepared to be used for compressive strength tests. (See heading entitled Strength Tests for the description and results of this experiment.) Six of these samples were treated as follows. Two 1-inch cubes each of obsidian, silicified coral, and Ocala chert were weighed prior to subjecting them to heat. They were placed in a Blue M Lab-Heat shuffle Furnace, heated to 1000C for 48 hours, removed, placed in a desiccator, and weighed after they were thoroughly cooled. They were then reheated to 100*C and left an additional 48 hours to determine if all the moisture that would be driven off at 100*C had been removed during the original 48-hour period. It had been removed, as was indicated by no change in weight. This same





24
procedure was followed for 1500C. 200*C, and so on through 5000C but it was not felt necessary to subject the specimens to such long periods of heat or to reheat them at each succeeding temperature since no additional significant weight loss occurred with prolonged heating or subsequent heating at the same temperature. (The validity of this procedure is established when the next experiment is described.) The results of this experiment are given in Table 1.

Twenty-six specimens consisting of samples from 14 chert nodules obtained from various areas of Florida plus one specimen of English flint were weighed, heated, reweighed, reheated, and reweighed again through successive temperatures to 500*C in the following way. After the initial weighing, the samples were heated at lOO*C for 54 hours after which they were removed from the oven while hot, placed immediately in a desiccator, and reweighed when thoroughly cool. They were returned to the oven and again heated to 100*C for an additional 4 hours and subjected to the same procedure as described above. This process was repeated until 5000C was reached. The oven was taken to the testing temperature at 500C increments, left at each increment for

1 hour, and then moved up. In other words, it took an additional hour to reach each succeeding temperature. The only variation which occurred within the experiment was that it was not considered necessary to subject the material to a total of 58 hours at each temperature as had been done at 1000C. The fact that no significant additional weight loss occurred by reheating at the same temperature justifies







TABLE 1


HEATING EXPERIMENT TO DETEiRMINE WEIGHT LOSS OF 1-INCH CUBES


Percentage Weight Loss
Sample

96 hra 14 ha 48 hr 48 hr 48 hr 24 hr 241-hr 24 hr 241-hr Total


Obsidian 0 0 0 0 0 0 0 0 0 0

Obsidian 0 0 0 0 0 0 0 0 0 0

Silicified
coral .36 .33 .04 .05 .11 .06 .15 .23 .0,7 1.410
Sil ic ified
coral .49 .33 .04 .06 .06 .14 .19 .19 .08 1.58
Oc ala
chert .32 .06 .01 .03 .04 .06 .17 .13 .07 .88
Ocala
chert .32 .05 .01 .02 .07 .09 .07 .15 .09 .87


a The total hours of heating for the 1000C and the 150*C increments actually were split (that is,, 48 and 48,, 72 and 72) to determine if additional weight loss occurred when reheated at the same temperature. When it was determined that no additional weight loss occurred these two times were combined and the procedure was discontinued.




26
the reduction in heating time. It should be pointed out that most of the samples tested did not exceed 20 grams. Had they been larger, longer heating periods might have been necessary. One sample, however, weighed 95 grams and the percentage weight loss for this sample was comparable to that of smaller samples of the same material. See Table 2 and Figure 2 for the results of this experiment. Figure 3 graphically illustrates typical weight loss patterns for Florida charts.

A number of samples which had been used for the

experiment described above together with their unheated controls were placed in moist pure quartz sand and left for one month. Water was added to the sand periodically to maintain dampness. Heated and unheated samples of the same material were kept as controls at room temperature. The purpose of this experiment was to determine how much moisture the already heated materials would absorb as compared to unheated samples subjected to the same conditions. The amount of moisture taken up by the heated samples was greater than that of the unheated. The heated and unheated controls left at room temperature during the month yielded some interesting information. The controls, that had already been subjected to heat, lost less weight than those which had not been heated. See Table 3 for the results of this experiment. The soaked samples were then subjected to heat to determine if there was any significant difference in the amount of weight loss between the heated and unheated samples or in the temperature at which the weight loss occurred. See




27
TABLE 2
HEATING EXPERIMENT TO DETERMINE WEIGHT LOSS OF SAMPLES FROM DIFFERENT LOCATIONSa
(Percentage Weight Loss
C 1000C 150C 2000C 250C 3000C 3500C 4000C 450OC 5000C Total S58 hr 40 hr 28 hr 22 hr 16 hr 8 hrb 9 hr 5 hr 4 hr
Ahl 1.08 .14 .05 .03 .05 .11 .15 .10 .15 1.86 Ah2 .67 .19 .11 .05 .03 .07 .13 .11 .11 1.47 Bh .67 .04 .02 .02 .02 .14 .14 .16 .12 1.33 Chl .38 .05 .02 .03 .02 .09 .11 .10 .11 .91 Ch2 .45 .02 .02 .02 .03 .10 .07 .13 .10 .94 Dh .57 .03 .01 .00 .03 .08 .13 .10 .10 1.05 Ehl .49 .01 .01 .00 .01 .06 .12 .09 .10 .89 Eh2 .38 .03 .02 .01 .00 .07 .10 .08 .06 .75 Eh3 .34 .02 .02 .03 .02 .03 .10 .09 .10 .75 Fhl .51 .04 .04 .02 .01 .07 .16 .15 .12 1.12 Fh2 .42 .07 .05 .00 .02 .08 .15 .09 .13 1.01 Fh3 .49 .02 .03 .01 .03 .05 --c .13 .10 -Gh .86 .03 .04 .03 .06 .10 .16 .12 .10 1.50 Hhl .92 .00 .04 .02 .00 .12 .15 .19 .18 1.62 Hh2 .63 ,06 .03 .00 .01 .08 .12 .15 .14 1.22 Ih .60 .09 .04 .06 .10 .14 .12 .19 .08 1.42 Khl .64 .03 .01 .01 .01 .04 .17 .13 .13 1.17 Kh2 .64 .04 .02 .01 .03 .08 .18 .16 .12 1.28 Mh .77 .08 .07 .05 .00 .09 .17 .16 .10 1.49 Nhl .49 .03 .03 .02 .02 .08 .13 .09 .15 1.04 Nh2 .35 .02 .03 .02 .01 .06 .13 .08 .14 .84 Nh3 .40 .04 .02 .03 .00 .09 .14 .13 .12 .97 Nh4 .44 .03 .03 .02 .03 .07 .15 .08 .11 .96 Ph .71 .15 .07 .03 .11 .11 .15 .13 .12 1.58 Sh .14 .04 .03 .01 .02 .00 .00 .00 .00 .24 Thl .88 .08 .05 .01 .02 .09 .15 .18 .11 1.57 Th2 .85 .05 .06 .01 .02 .10 .17 .17 .15 1.58
aSamples A and P are silicified coral; samples B, C, and E are cherts from High Springs, Florida; S is English flint; all other samples were obtained from differing locations such as Johnson. Lake in Levy County, three miles north of Ocala in Marion County, and from Alachua County. All of these samples were heated twice at the same temperature but the results were combined because the second heating produced no significant additional weight loss. It should be pointed out that if the total period of heating at 450*C had been for a longer duration perhaps there would have been less weight ldss at 5000C and thus would have resembled more nearly the results of Table 1.
bThese samples were heated for a total of 12 hours but the results of the second test of 4 hours were not reliable.
OThis sample fractured at 4000C.





1.86%





Silicified Coral


. 33%
1.00

M
o Chert, High Springs

.-P
bo

S1.00 1.12%



Chert, Ocala


.1.00 55%
1.00



Chert, Johnson Lake 100 200 300 400 500
Degrees Centigrade Figure 2.--Weight Loss upon Heating of Cherts from Various Locations in
Florida (note the rapid increase beginning around 350*0).

























I

S.45-1

- .40. ---- = Johnson Lake Chert, Levy County,
Florida
35-'
- = Chert from York's property, NX Alachua County, Florida
.25,.

.20l



015.



I I I a a I a
100 150 200 250 300 350 400 450 500 550 600 Temperature (C)

Figure 3.--Weight Loss of Samples of Florida Chert Illustrating the Typical Pattern Observed for All Florida Specimens Tested Throughout a Two-Year Period (Obsidian, Arkansas Novaculite, and English Flint did not follow this pattern).







TABLE 3


RESULTS OF EXPERIMENT CONDUCTED TO DETERMINE ABILITY OF HEATED ROCK SAMPLES TO TAKE ON MOISTURE


MoeihtGiste and Bath h a Weight Loss of Control after
Sample a Wi in te Oane Month Sample One Month at Room Temperature

24 hr after 4 Days after
Removal Removal
M% M%

Ah .57 .53 Ah .01
Ah .45 b .42 A .06
As .27(lost)b .39(lost) Eh .00
Eh .95 .27 E .05
Eh 1.13 .35 Fh .00
Es .55 .09 F .08
Fh .18 .15 Rh .08
Fh .09 .03 H .08
Fs .04 .00 Nh .01
Rh .56 .44 N .06
Rh .72 .30 Th .00
Ha .42 .21 T .00
Nh .27 .21
Nh .26 .18
Ns .12 .01
Th .44 .36
Th .44 .40
Ta .28 .18

ah following the sample letter indicates that it has been heated; sfollowing the sample indicates that it was soaked but not heated; a letter with no h or s following it is an unheated and unsoaked control. The tremendous difference in weight after four days in the E series may be because it is more calcareous.
b It is difficult to account for this anomaly unless an error was made in
the original weight.





31
Table 4 for the results of this experiment. It was hoped that this experiment, though simple, might prove to be a reliable and inexpensive method to be employed by archaeologists to determine if chipped stone remains had been thermally altered. This will be discussed further under the heading Archaeological Application, but although there is a fairly consistent difference in weight lost on an intrasample level, on an intersample level there is overlap. Therefore, even if an investigator knew a great deal about the rock he was recovering (that is, source, composition, etc.), he would have to be careful in assigning too much importance to weight loss. This experiment also indicates that the weight loss at 1000C is probably not too indicative since it would fluctuate greatly depending on how damp conditions were prior to heating. It has been demonstrated that an appreciable change in weight occurs if the samples are left at room temperature after being removed from a moist environment (see Table 3).

Materials from the field which were thought to have been thermally altered since they were quite lustrous and many exhibited a pinkish cast were heated in order to compare weight losses with other specimens that were known not to have been previously heated. The results are given in Table 5. If this table is compared with Table 2. it is apparent that there is no significant difference in the amount of moisture given off between the materials that had been suspected of being previously heated and those which were being heated for the first time. The results of this








TABLE 4

HEATING EXPERIMENT CONDUCTED TO DETERMINE DIFFEREiNCES IN HEATED AND UNHEATED SPECIMENS AFTER SOAKING FOR ONE MONTH

Wt Loss after 24 hr Additional Wt Loss after Sample at 1000C b24 hr at 350*0C
(%)a M(b)c


Ah .42 .38 .18
Ah .40 .37 .12
As .91 .79 .32
Eh 1.08 .40 .03
Eh 1.29 .51 .03
Es .89 .43 .16
Ph .50 .47 .03
Ph .22 .16 .17
Fs .61 .57 .27
Hh .86 .74 .08
Hh 1.07 .65 .35
Hs 1.00 .79 .25
Nh .53 .47 .05
Nh .57 .49 .04
Ns .65 .54 .23
Th .55 .47 .08
Th .49 .4-5 .10
Ts .87 .77 .35


a Calculated from weight of from moist sand bath. b Calculated from weight of
from moist sand bath.


samples 24 hours after samples four days after


c While there appears to be a slight, yet unreliable tendency for the weight loss to be greater at 10000 for the unheated soaked samples, the greater weight loss is quite consistent for the unheated soaked samples between 10000 through 35000. Because there is overlap in percentages between heated and unheated depending on the sample involved, this method, while consistent within samples, could not be used as an archaeological application. Even if the investigator had a profound knowledge of the materials with which he was dealing the results would be tenuous.


removal


removal










TABLE 5

HEATING EXPERIMENT CONDUCTED TO DETERMINE
ARCHAEOLOGICAL SPECIMENS SUSPECTED OF THERMALLY ALTERED


WEIGHT LOSS OF
HAVIYTG BEEN


Weight Loss
Sample After 24 hr After 24 h Total
at 1000C at 4000C
M% M% M%


.19 .28 .27 .39
.45 .35

.47 .36 .44 .22 .35

.27 .25 .42


.68 .76 .78

.41 .56

.85 .52 .55 .69 .38

.52

.40 .48 .59


.87 1.05

1.05 .81 1.01

1.20 .99 .91 1.13 .60 .87 .67 .73 1.01





34
comparison plus the data derived from soaking samples for a month in a moist sand bath indicate that it is not possible to use weight gain or loss as a reliable criterion in determining if archaeological specimens had been subjected to heat.


Decrepitation and Explosion

It was no mystery to primitive man that fire could be destructive to rock (see Literature Review), but this investigation has attempted to demonstrate that when siliceous rock materials are cautiously subjected to heat, an alteration occurs which conferred an advantage to prehistoric man in the manufacture of his chipped stone implements. Man had many thousands of years to discover this fact and to perfect the technique. Since the use of fire and the use of stone were two of the earliest and most important items in the inventory of a physically and culturally evolving creature, it should come as no surprise that he gradually acquired an intimate knowledge of their attributes. The observations to be discussed below are probably much like those made long ago.

The materials involved in these experiments were all Florida charts. Reactions might occur at different temperatures, or not at all, if other rock types were used. Sufficient samples of non-Florida materials were not available for experimentation. These should be tested eventually because the results would certainly be enlightening.

Webster's New World Dictionary of the American

Language (1970) defines decrepitate: "to roast or calcine





35
(salts, minerals etc.) until a crackling sound is caused or until this sound stops; to crackle when exposed to heat." Explosion occurs when the stress that is causing decrepitation exceeds the elastic limits of the material.

When this study was initiated, several large chert flakes were prepared in order to test their reaction when heated. The author had intended to raise the temperature slowly according to Crabtree's (personal communication) instructions but the oven was progressing in degrees centigrade while the author, unfortunately, was thinking in degrees fahrenheit. The oven consequently heated more rapidly than anticipated. At 4001C the rocks exploded. The results are shown in Figure 4. Subsequent experiments, conducted to determine the reasons for the rock failure.,, resulted in one of the major contributions of this study.

Figure 4 illustrates quite clearly several facts that refute objections which may be raised with regard to the intentional heating and subsequent flaking of lithic materials. The picture shows potlid fracturing and blocky, angular flakes with no bulbs of percussion. This kind of debris does not occur by intentional flaking. It differs markedly from the thinning flakes found on archaeological sites that are suspected of being thermally altered. It resembles exactly what one would expect to result from too rapid expansion and contraction as might occur in a forest fire or if a rock had been placed in or near a hearth. Subsequent testing of Florida charts has revealed that:




































Figure 4.--Explosion Resulting from Too Rapid Exposure to Heat (note "potlids" and blocky angular flakes).






1. No spalling occurred (except on rare occasions)
when the temperatures were raised very slowly.

2. No explosion occurred even when the temperature was raised rapidly to 35O*O, allowed to remain at 35000 for 24 hours, and then moved to 400*C.

3. Explosion occurred on all occasions at 4009C when the material was taken to 400%C without allowing
the temperature to be raised slowly or at least
leaving it at 350@C for an extended period. Smaller
specimens did not explode as readily.

4. If the temperature was raised rapidly, explosion,
or at least some spalling, occurred whenever the
material was removed from the oven at 40000 without
allowing it to cool first.

5. If the temperature was raised rapidly, explosion, or at least some spalling, occurred occasionally but not often when the material was removed from
the oven at 3500C without allowing it to cool first.

6. Explosion did not occur at 300*C even when the material was removed from the 30000 oven immediately.

7. Interestingly, explosion rarely occurred at any temperature when the material was removed immediately from the oven if' the temperature had been
raised slowly and maintained at the testing temperature for a sustained period.

8. Explosion never occurred when the material was
tested a second time at the tame temperature.

9. When the temperature was raised rapidly a crackling noise (decrepitation) was often heard at 35000 and
always heard at 4I000C when the material was removed
from the oven without allowing it to first cool.
It was not heard at 3000C nor was it heard when
materials were heated for a second time.

10. When samples were placed directly into a preheated
oven at 3500C no reaction occurred after 1/2 hour but all except a sample of Ocala chert snapped in
half when removed from the hot oven and exposed to
air temperature.

11. When samples were placed directly into a preheated
oven at 4000C, explosion commenced after approximately 20 minutes. The oven was turned off immedifately; explosion continued intermittently until
the oven cooled to about 37500. All samples had
exploded, including Ocala chert, with the exception of a sample of High Springs chert which did iiot snap
even after removal from the hot oven.





38
Two samples that had been heated to 350*C for

24 hours were removed from the oven with tongs while hot (still 3500C); the tongs were warmed on the side of the oven before touching the hot stone. One of these samples snapped in half with a very loud sound (room temperature was about 75*C). Cold water (tap water) was dripped along the edge of the samples with a dental syringe to see if they would flake--they did not! (See Literature Review for accounts describing this alleged phenomenon.) The samples were then placed directly under the tap and cold water allowed to flow over the entire sample. This resulted in an audible hissing sound and a crazing of the material. The same procedure was followed with two samples that had been left at 400*C for an additional 6 hours. Crazing occurred and subsequent attempts to flake the material caused it to crumble. It was impossible to pressure flake this material because the flakes could not be removed in a predictable way. The specimen literally fell apart (see Figure 5).

Failure on quenching was shown by irregular cracks
differing in appearance from the smooth conchoidal
fractures . . . (Pressler and Shearer 1926: 308).

Other experiments were conducted to test the

significance of the crackling sound which occurred when specimens were removed immediately from a hot oven. These experiments will be discussed at the end of this section and in those dealing with Petrographic Analysis and Strength Tests.












a


Figure 5.--Results of Experiment Conducted to Test the Validity of "Flaking" Hot Stones by Dripping Cold Water on Them: (a) The Rock Literally Fell Apart when Flaking Was Attempted (note deviation from conchoidal fracture typical of flint materials); (b) Magnified Area Illustrating the Crazing which Occurred.


1 VEX^
nro,






Vitreousness

To vitrify is to convert into, or cause to resemble, glass or a glassy substance by heat and fusion. The more vitreous an object is, the more it has the luster of broken glass. In order for a cryptocrystalline rock to be converted into an amorphous, noncrystalline structure, it is necessary to subject it to temperatures of ca 1400-1700*C (approximately 3000*F). Aboriginal peoples in the state of Florida could not achieve or maintain temperatures this high. This fact is known by the quality of the pottery remains which indicates that pottery was fired at a much lower temperature--probably not over 5500C (ca 10000F). Since the practice of altering lithic materials seems to have occurred on preceramic levels in Florida, it could not be assumed that earlier inhabitants were capable of producing temperatures higher than their descendants. Besides, from petrographic analyses, which will be described later, it has been demonstrated that the size of the cryptocrystals does not change even though vitreous luster occurs after heating.

Florida cherts are characteristically nonlustrous and coarse grained except for an area directly under the cortex which may be as thin as 1/8 inch or as thick as several inches, this latter being exceptional. Occasionally, however, the chert is slablike and ledgy not exceeding an inch or two in thickness. When eert like this is found, the fine grained area generally extends from cortex to





41
cortex throughout the entire thickness of the rock and is extremely glass-like and homogeneous. Typically, however, the chert is found in thick rounded nodules or beds and the fine grained area under the cortex rapidly shades into a coarser grained area farther within the mass. The reason for this difference in texture is not clear but it occurs during replacement of the limestone by silica and might be "due to a descreasing rate of precipitation because of the diminishing rate of supply of solution as consolidation proceeds" (Folk and Weaver 1952: 500-1).

The smaller the size of the cryptocrystals, the

more the material will exhibit the vitreous luster of glass on a fractured surface, and by contrast, the larger the cryptocrystals, the less lustrous is the aggregate mass in appearance. Interestingly, after coarse grained cherts are heated slowly to around 3500C, left for a period of time, and subsequently fractured, the fractured surface exhibits a glass-like luster but the grain size has not been changed. The reasons for this are quite simple and will be explained in the discussion which follows. Table 6 summarizes experiments using large and small samples of cherts from different rock masses and locations. These tests were conducted to determine the length of time necessary to effect alteration which results in a vitreous fractured surface. Each group of samples heated at each temperature was taken to 1000 C and left for 2 hours after which they were raised by 5000 increments for 1-hour periods













TABLE 6


HEAT SOAKING EXPERIMENT CONDUCTED TO ASCERTAIN LENGTH OF
TIME NECESSARY TO EFFECT THERMAL ALTERATIONa


Sample Hours at 350C Hours at 400*C
No.
2 4 6 8 10 12 2 4 6 8 10 12


40 + ++ ++ ++ + + ++ +++ +++ +++

50 + + ++ ++ ++ +++ + ++ ++ +++ +++ .

60 ++ ++ +++ +++ +++ +++ +++ +++ +++ +++ +++ +++


a If the space is left blank no change in vitreousness or flaking ease has occurred; + means change is slight; ++ change is pronounced; +++ change is complete. There was only occasionally noted a difference with regard to change and sample size. The smaller samples weighed approximately 3-8 grams; the larger samples weighed 50-80 grams. More attention was paid to thickness in selecting the sample than weight. Extreme crepitation occurred in the samples heated this rapidly to 400@C and in this regard, the larger samples were more involved than the smaller samples.





43
to either 350*C or 400*C as indicated, and then left at the ultimate temperature for the designated period of time. The oven was shut off and the samples allowed to cool in the oven. The gradual onset of vitrification seems to go hand in hand with an increasing ease in removing flakes. If alterations take place too rapidly, dramatic, destructive events occur. It should be emphasized that vitreousness is not apparent unless the rock specimen is broken or chipped after heating. The exterior surface of the heated stone remains dull. This is illustrated in Figure 6b.


Discussion

The information presented to this point has been

mainly observation and description. The data now remain to be interpreted and the significance of the experiments discussed.

It seems fairly clear that no reliable inferences can be made from differences in weight loss and gain to help in determining if archaeological specimens have been thermally altered. Even under controlled conditions, though significant differences were observed for the same rock when flakes were either subjected to heat or kept as controls, nothing reliable was recorded when making comparisons between different rocks even when the method of exposure was identical.

In addition, the amount of water driven off, whether great or small, made no difference in the change which ultimately resulted as long as the temperature effecting





















































Figure 6.--Vitreousness Occurring when
Florida Cherts Are Heated and Subsequently Flaked. Top: Specimens were Heated Slowly to 3500C. Left for 24 Hours, and Cooled in the Oven. Bottom: Specimen was Heated slowly to 5000C, Left for 5 Hours, and Removed Immediately from the Hot Oven (note relict dull area that has not been flaked after heating).





45
the change was reached an~d maintained until the change occurred. Obsidian (Table 1) lost no weight at all but other tests suggest that a change might occur (see section on Strength Tests). A quartz crystal and pulverized quartz lost very little weight (after 24 hours at 350w C they had lost .01% and .04%, respectively), but it has been stated that quartz becomes easier to flake (Crabtree, personal communication; Man 1885: 580). English flint lost only about .15% to .25% and, because it is fine grained, we suspected that fine grained Florida cherts would lose little weight and coarse grained Florida cherts would lose more. However, there does not seem to be any significant, predictable difference between the amount of weight lost and crystal size in Florida cherts. This could be due to heterogeneities since even fine grained materials may have large void spaces that cannot easily be detected. It is more likely because, even though there is less water in any given interstitial space when the crystals are small, they are still anhedral and probably are not packed any better than larger ones; therefore, the same amount of water exists even though the crystals which it surrounds differ in size. The difference in weight loss for English flint compared to Florida chert might be due to the conditions under which they were formed. Florida cherts probably contain more water vacuoles. The cryptocrystals of English flint are probably more closely packed. The smaller the size of the crystals, the greater the surface area unless the crystals are intergrown.





46
If opal were present it might be a simple matter to

explain what occurs when water is driven off through heating: the opal when dried would crack and adhere more firmly to the microcrystals exactly as jello would tend to stick to the side of a glass. This might result in a binding of the microcrystals. The presence of opal as interstitial material in chert, however, has been quite thoroughly dismissed (Folk and Weaver 1952; Schmalz 1960). Attempts to detect the presence of opal in this study produced only negative results.

Despite the discouraging comments thus far, the loss of water which occurs when cherts are heated is a very significant factor in the alteration of the rock. With the removal of the intercrystalline water, the microcrystals become firmly cemented. Thus when a fracture occurs it passes through rather than around the individual crystals. In other words, the stone breaks more like glass than a rock aggregate even though the same microcrystalline structure and texture are still present. This, in turn, explains the increase in vitreousness of the fractured surface. Chert is composed of microcrystals which constitute the mineral phase known as chalcedony. Mineralogically, chalcedony is waxy or greasy in luster but individual faces of this mineral are normally not seen because the crystals are anhedral (no definite shape or orientation), usually subequidimensional, and microscopic. Therefore, when fracture occurs, especially if the rock is coarse grained, the





47
fractured surface is dull due to refraction and poor reflection. After heating, the fractured surface is vitreous due to the greater transmittance of light which occurs when the fracture passes through successive microcrystals and intercrystal spaces revealing the intragranular nature of quartz.

If the material is fine grained, it seems to alter

slightly faster which may be because, even though it contains the same overall amount of water, there is less moisture being removed from any given interstitial area. There seems to be no correlation between crystal size and the temperature at which alteration occurs in Florida charts. There does seem to be some correlation between the composition of the chert and the length of time as well as the temperature at which alteration occurs. The fact that Florida charts are formed as limestone replacements was discussed in the section on Materials. Some of the materials tested appeared to react differently than others in that they did not respond at the same temperatures or time periods; also they did not decrepitate or explode. Except for the area directly under the cortex which always seems to be very siliceous, a satisfactory change did not occur in some rocks at the testing temperatures which usually effected a change.

When temperatures are raised slowly and left at

either 3500C or 4000C a change occurs which is very apparent when the sample is subsequently flaked revealing a vitreous fractured surface. In addition, it is definitely easier to manufacture stone implements (see Figure 6a). This statement





48
is not based entirely on intuition (see section on Strength Tests). It remains to be explained, however, why it is that if the temperature is raised too rapidly, explosion occurs. The originalweight loss at 100*C is due to the removal of adsorbed water held on the surfaces of the individual microcrystals. After this initial large water loss, the weight remains quite stable until 350*C. Prior to this, the temperature probably has not been high enough to remove the chemically bound water held in the intercrystalline areas. I suspect that the following happens: 350*C is probably a sufficiently high temperature for alteration to take place if this temperature is sustained for a long period of time (see Table 6). If the temperature is raised to 400*C prior to the gradual removal of the chemically bound water, explosion results because the alteration proceeds too rapidly. Vitrification is always evident, at least to some extent, on the fractured surfaces which result from these explosions. Therefore, some change must occur almost immediately when a critical temperature is reached even though the material blows up at the same time. There does not seem to be any previous study dealing with this problem adequately. Preston (1926) in his article on the rupture of glass discusses the fact that glass will fracture when alternately subjected to heat and cold. But his work mostly describes the type of fracture which will occur depending on the stress to which the material is subjected. Perhaps the answer lies in the following statement:




Ila
r./
principles of surface chemistry . . . . When a
crystal consists of highly polarizable anions of large
size, together with small, highly charged cations,
then the anions will be pushed to the surface of the crystal and the cations will be recessed. Thus in a microerystal of quartz oxygen ions predominate at the surface, while the silicon ions are depressed. It is believed that each microcrystal of quartz then has a
negatively charged "skin," and effectively repels
adjacent randomly oriented microcrystals . . . fracture
probably takes place between the polyhedral blocks because of the surface repulsion forces (Folk and
Weaver 1952: 507-8).

When the rocks are subjected to critical temperatures, there may be a change in the position of oxygen and silicon ions as described above. If the ions become too excited when temperature is applied rapidly, explosion may take place. This may also explain the clicking sounds which occur and often result in exfoliation when the material is rapidly cooled. Perhaps the reason these clicking sounds aren't heard when the material is removed after a sustained period is because the process is completed and no further change is taking place.

Failure was accompanied by peculiar "clicks." These "clicks" were heard early in the cooling period and
never during the heating period, when the rate of temperature change was lower. When the cups were
heated to a slightly higher temperature, no higher
percentage of failures was observed (Pressler and
Shearer 1926: 307).

Material that has been heated to 5000C is no easier to flake than that left at 350*C for prolonged periods (see Fig. 6b). A number of samples were heated to 600*C; subsequent chipping of these specimens did not reveal any further change either. However, point tensile strength tests, to be discussed later, do not support this observation since there is increased strength loss with increased temperatures under point tensile





50
load. In addition, while there is no apparent increase in flaking ease, quite often attempts to chip flint materials that had been heated to 500*C-6000C or had been heated to 3500C-400*C and removed immediately from the hot oven, resulted in a lateral snap due to end shock. This fracture did not occur at the point of impact. The fractured surface often resembles that illustrated in Figure 8. Flintknappers are familiar with this type of failure since it occurs when a substantial blow is imparted to a rock whose mass is not adequately supported to absorb the shock. With these heated materials, however, failure occurred when only slight pressure or percussion was applied.

The composition of the chemically bound water may not be identical to water as we normally think of it, that is H 20. If the hydrogen and oxygen ions are dissociated and the oxygen plus part of the hydrogen are given off when a certain temperature is reached, the remaining hydrogen ion with its positive charge may hook up with the negatively charged oxygen "skin" of the microcrystal and serve as the binder. Or if the depressed silicon ion is agitated, it may hook up with an oxygen ion from an adjoining microcrystal and thus form the bond in that way.

Pressler and Shearer (1926) offer some suggestions concerning the reactions of various types of flints when heated. Their article is concerned primarily with flints used in the ceramic industry but may hold some applicable clues. Since temperatures of l140C-l7OO0C (>30000F) are






51
needed to transform microcrystalline structures to a noncrystalline form, the vitrification which occurs when flint materials are heated to only 350*C must be accounted for in another way.

The impurities in flints generally act as fluxes,
due to eutectic developments.
Fe 2 0 was found in all flints varying from
0.03 to 0.12 p~r cent. While iron is objectionable
as an impurity because of its discoloring effects,
the small percentage present in the flints would
probably be of no significance in a body composition.
Some of the American flints are free from CaO. and
others contain generally less than the French flints.
The loss on ignition varies from 0.13 to 0.85 per cent
and represents CO dissociated from CaCO . and adsorbed or chemical combined water (Pre~sler and
Shearer 1926: 292-3).

If the impurities (or combinations of impurities) contained in Florida cherts are serving as fluxes (substances promoting fusion) to fuse a thin surface film of the cryptocrystals, then change will occur when the melting point temperatures for these impurities are reached (eutectic development). If this is the case, answers are found for two puzzling problems: (1) why vitrification occurs at such a low temperature (3500C), and (2) why some materials do not respond at the same temperatures--the melting points of the fluxes are probably different. If the percentage of calcium is quite high, this also explains why certain materials do not make a desirable change despite the temperature or length of the heating period. Calcium will serve as a flux if present in small quantities, but prevents the desired reaction from occurring if present in large quantities. Three Florida cherts, which responded




52
differently when heated were submitted to the Soils Department at the University of Florida for Atomic Absorption Spectrophotometer analysis. The results of this analysis are given in Table 7. It is not known what percentage of calcium is necessary to prevent the desired reaction but it is interesting to note that Ocala chert and High Springs chert had considerably higher percentages of calcium than

the two Johnson Lake specimens. The Ocala and High Springs cherts consistently reacted differently than Johnson Lake and other Florida materials tested in that the expected change did not occur within the same temperature and time ranges.

Figures 7, 8, and 9 illustrate various types of

fractures. Figure 7 shows an example of a potlid fracture which occurred only when the materials were heated too rapidly. Figure 8 shows the type of fractured surface which often occurred when the samples were removed from a hot oven to a cool environment. The specimens in Figures7 and 8 have broken with a conchoidal fracture typical of flint materials. Figure 9 is a thinning flake, intentionally struck from an obsidian core. In addition to the conchoidal fracture, this last specimen possesses a welldefined bulb of percussion not present in Figures 7 and 8. Figure 9 serves as a reminder that a microcystalline rock will break with a conchoidal fracture but no bulb of percussion will be evident unless impact has taken place.

The results of the heating experiments establish quite clearly that crystal boundaries may be a disturbing











TABLE 7


RESULTS OF ATOMIC ABSORPTION SPECTROPHOTOM~'ETER ANALYSIS


Percentage
Samle g Fe Ca P ?ln K


Johnson Lake
(fine grained) .010 .250 .033 .003 .015 .040
Johnson Lake
(coarse grained) .008 .400 .045 .016 .010 .020

High Springs .011 .1115 .095 .033 .010 .042

Ocala .040 .290 6.600 .040 .025 .050























































Figure 7.--Example of a Potlid Fracture which Often Occurred when Florida Cherts Were Subjected too Rapidly to 4000C Temperatures.






















































Figure 8.--Examples of a "Crenated" Fracture which Often Occurred when Specimens Were Removed Directly from a Hot Oven to a Cool Environment.



















































Figure 9.--iSpecimen Depicting Intentional Fracture with Bulb of' Percussion and Typical Fractured Surface Emphasizing that Impact Has Occurred.





57
influence when attempting to predict fracture. Therefore, the more glass-like the material, the more predictable the fracture. Heated cherts are more glass-like and fractures are not only more predictable but easier to execute.


Iron Content of Florida Chert

The incorporation into chert formations of concentrations of iron which impart a pink to red color upon heating is usually because of secondary enrichment resulting from the mobility of iron in iron-rich paleosoils or bog deposits. In some of the Lower M~iocene deposits, however, another situation exists in which iron seems to have been incorporated at the time of silicification which resulted in the chert formation. In addition, although they are rare, bright pink colors (ca 5 R 7/4) (lMunsell 1946) are sometimes found in cherts imbedded in terra rossa residual soils on Ocala Limestone. These cherts are dull or earthy in appearance and do not resemble cherts which have been thermally altered (H. K. Brooks, personal communicationn.

Color change takes place between 240*C and 2609C in Florida cherts. Figure 10 illustrates the variation which results depending upon the amount of iron present in the sample. Unfortunately, true color representation was not attained but an analysis of the iron content (see samples in Figure l0b) revealed that samples changing from 10 YR 6.5/2 (between very pale orange and pale yellowish brown but nearer the latter) to 10 R 4/4 (between pale reddish brown and dark reddish brown) contained 4000 ppm



















































Figure lO.--Heated Specimens and Unheated Controls Illustrating Degree of Color Change Depending upon the Amount of Iron Present in the Chert.





59
(.4i0%) of iron. Those changing from N 6.5 (between light gray and medium light gray) to 5 R 7/2 (between grayish pink and pale red) contained 2500 ppm (.25%1). Those exhibiting no color change contained 1100 ppm (.11%). It should be emphasized that:

1. Color change occurs only because of the oxidation
of iron and will not occur if no iron is present.
Many samples of Florida materials did not change
color.

2. The temperature at which color change occurs
(240*C-260*C) is not synchronous with the change
to vitreous luster in Florida materialsca 3500C-4000C for sustained periods.

3. Therefore, color change cannot be used as a reliable
criterion (at least for Florida cherts) in ascertaining if materials recovered from archaeological
sites have been intentionally thermally altered.
But if a combination of vitreousness and color
change occur frequently on artifacts or waste
flakes as is the case in Florida, the assumption that man was subjecting the chert to temperatures
sufficiently high to cause a change prior to final
chipping is valid.


Strength Tests


Preparation of the Samples

Uniform-sized samples were prepared in order to determine, by standard rock mechanics tests, whether any differences in compressive and point tensile strength exist between heated and unheated specimens.

Initially, twelve 1-inch cubes were prepared, each weighing approximately 42 grams. Using a diamond blade, it was necessary to saw the stone as accurately as possible to the desired dimensions and then laboriously grind the samples to exactly one inch. Any deviation would have rendered the results unreliable. Since this method was extremely





60
time consuming, a coring device was used which greatly reduced the time needed to prepare samples. Using a drill press as a basic piece of' machinery (Figure lla), a Corematic diamond core bit having an inside diameter of' 1 inch � .005 with a 6-inch core barrel and 3/8-inch diamond penetration was constructed by Anton Smit and Oc., Inc., New York. This is a variation of' a Corematic drill used to cut holes in glass. The chert nodule to be cored was clamped into position as illustrated in Figure llb.

The diameter of' these cored samples was exactly one inch. The cored samples that were to be used for compressive tests were then sawed as close to one inch in length as possible and ground to precisely one inch. This reduced the number of' surfaces to be ground from six for the cubed samples to two for the cored samples. The cored samples that were to be used for point tensile strength needed no additional preparation.


Compressive Tests

Of the original twelve 1-inch cubes, six were heated to 5000C as described in the section on Heating Experiments and six were kept as unheated controls. One sample each of heated and unheated obsidian, silicified coral, and chert from a quarry 3 miles north of Ocala 1 were used for compressive tests. Compressive strength data obtained from the cubed samples of Ocala chert were unreliable due to error in testing; these were discarded. Subsequently, two cored


1 To identify this material as to location it will hereafter be called Ocala chert.

















































Figure 11.--Composite Illustration of: (a) Drill Press,
(b) Corematic Diamond Core Bit, and (c) a Chert Nodule with Cores Removed to be Used for Strength Tests.





62
samples of Ocala chert, 1 inch in length, were prepared. One of these was heated to 4000C and the other was kept as an unheated control. Both cubed and cored heated samples had been removed from the oven immediately at the end of the heating period without first being allowed to cool. The significance of this procedure will become apparent later.

Arrangements were made with the Civil Engineering

Department at the University of Florida to test the strength of these materials. The equipment used was a 300,000-lb capacity Riehle Universal testing machine with hydraulic type loading and five ranges. The results are given in Table 8. The cross sectional area of the cored samples was standardized to 1 inch as follows: A =-rir 2

A = .785

The figures resulting from the compressive strength tests for the cored samples were then divided by .785 thus expressing the force in pounds of pressure per square inch.

In another test, cored samples of obsidian and High Springs chert were prepared for compressive strength tests as described above. One sample of each of these materials was heated to 400*C and allowed to cool in the oven. One sample. of each was retained as an unheated control. The results are given in Table 9. See Figure 12 which graphically illustrates the data presented in Tables 8 and 9.

The compressive tests yielded the following results. From the data given in Table 8. it is apparent that when









TABLE 8

RESULTS OF COMPRESZ"IVE STRENGTH TESTS WHEN
HEATED SPECIMENS ARE SUBJECTED TO A COOL
ENVIRONMENT WHILE STILL HOT


Unheated Strength
Sample Control Heated Loss
(psi) (psi) M%


Obsidian X 50,100 50,000 40
Silicified
coral 43,900 25,000 43

Ocala chert 52,994 319720 40


TABLE 9

RESULTS OF COMPRESSIVE STRENGTH TESTS WHEN HEATED
SPECIMENS ARE ALLOWED TO COOL IN THE OVEN

Unheated Increase in
Sample Control Heated Strength
(psi) (psi) M%


Obsidian Y 31,100 39,600 25

High Springs
chert 25,100 42,200 40

















Ocala Chert Silicified Coral Obsidian X High Springs Chert Obsidian Y


Decrease in Compressive
Strength


I I I I I I I


,50 40 30 20 1-0 0


Increase in Compressive
Strength


10 20 N0 40 50


(p6)


Figure 12.--Decrease or Increase in Compressive Strength over Unheated Controls of Heated Specimens; Samples Showing a Decrease Had Been Removed Immediately from a Hot Oven while Samples Showing an Increase Had Been Cooled
before Removal.


I


I

I I a liii I.!





65
siliceous materials are heated to temperatures of 400OC5000C for sustained periods and removed while hot, certain stresses occur which cause a reduction of strength when compared to the unheated controls. The three unheated varieties withstood forces ranging from 44,000 to 53,000 Psi (rounded figures) while the heated samples of the same materials ranged from 25,000 to 32,000 psi. This represents approximately a 40% reduction of strength in the heated samples. On the other hand, when the heated samples were allowed to cool in the oven, as shown in Table 9, there was an increase in strength amounting to approximately 25PIo for obsidian and 40% for the High Springs chert. Cohering the material without the introduction of stresses allowed the heated samples to resist failure for a longer time than unheated counterparts or heated specimens that had been stressed by sudden subjection to a cool environment.

No comparison should be made between the pounds of pressure per square inch recorded in Tables 8 and 9. The experiments were conducted several months apart, the equipment was operated by different individuals, and the rate of load was not observed for the samples removed from the hot oven and their controls. The rate of load for the Table 9 samples was approximately 20,000 pounds per minute. In addition, and most importantly, the samples were different. The obsidian samples were from different locations and therefore probably of different ages and depositional situations. The reader is reminded that man has classified





66
both of these specimens as obsidian based on certain arbitrary attributes shared by both; the use of other attributes may have resulted in a different category for each. Of significance here is the reversal of the amount of pressure needed for fracturing the material depending on whether the rock was removed from a hot oven or was first allowed to gradually cool in the oven.


Point Tensile Tests

A jig was machined to apply stress to the cores as

described by Reichmuth (1963). This jig was used in connection with the Riehle Universal testing machine described previously. The jig was constructed to apply point tensile load to the curved surface of the cylindrically cored specimen with the long axis of the specimen placed horizontally and at right angles to the loading jig. The jig was constructed so that the point compressive loads were applied through small diameter steel hardened dowel pins with rollers manufactured by Holo-Krome of West Hartford, Connecticut (see Figure 13). The cones of percussion induced at the points of application of compression produce internal tensile stresses perpendicular to the load axis.

Cored samples, one inch in diameter of varying

lengths were prepared as described earlier. In the first experiment, two cored specimens of Ocala chert were heated to 4000C for 24 hours and removed immediately from the hot oven at the end of the heating period; two samples were retained as unheated controls. The results of this





































Figure 13.--Composite Illustration of: (a) Compressive Strength Testing Nachine, (b) Close Up of Jig with Core in Position, and (c) Core Split by Application of Point Tensile Load.





68
experiment were as follows. The unheated Ocala chert withstood forces averaging 2700 Psi while the heated Ocala chert withstood forces averaging 1500 psi. This represents a reduction in force by /+5% needed to break the material. The point load tensile strength was computed from the following empirical expression given by Reichmuth (1963):

T = .963-L- where


T = tensile strength

F = total failure load in pounds D = core diameter in inches The information to be gained from point tensile

tests was considered pertinent to this investigation because the amount of force used to induce failure of the material by point tensile stress is essentially the same as the strength needed to induce fracture when manufacturing lithic tools from siliceous materials by either percussion or pressure methods. Therefore, extensive experiments were set up to test the point tensile strength of differing materials in various ways.

1. Four samples of obsidian, High Springs chert, and Johnson Lake chert were tested as follows and allowed to cool in the oven:

1 sample of each used as controls
1 sample of each heated to 30000 for 24 hours 1 sample of each heated to 35000 for 24 hours 1 sample of each heated to 40000 for 24 hours

2. Two samples of obsidian and of Johnson Lake dhert (from same core as Johnson Lake chert used above)





69
were heated to 3000C and 350*C left for 24 hours, and then removed immediately from the oven.

The results of these tests are given in Table 10. In all samples except obsidian for which the data were not consistent, there is an increasing reduction in strength with increase in temperature. In addition, though admittedly the data are scant, there is an even greater increase in reduction in strength when heated samples are removed immediately from the hot oven.

If a comparison is made between the results obtained for compressive tests with those for point tensile, a discrepancy seems to exist. Under compressive strength when samples are allowed to cool in the oven they resist failure longer than unheated controls. The results of point tensile tests, however, revealed a significant reduction on in the time and load necessary for failure to occur in heated:samples regardless of whether they were removed from the oven while hot or allowed to cool in the oven. This seeming paradox is easily explained. The binding of the microcrystals which occurs when the rock is heated adds compressive strength through cohesion to the structure. The increase in homogeneity which increases strength under compression is the very factor which decreases point tensile strength: (1) the individual microcrystals are bound more firmly together;

(2) therefore, when the flaw is introduced which is preliminary to and necessary for fracture to occur; (3) failure takes place more readily because the specimen fractures more like glass than a rock aggregate. The added decrease in







TABLE 10


RESULTS OF POINT TENSILE STRENGTH TESTS a


Unheated 3000C j3500 C 4000C Total Strength
SamleControl Allowed to Cool in Oven M%


Obsidian 1872 26410 1536 2252
1944 1416 1368 b

High Springs
chert 2568 2448 2156 1584
1680 39

Johnson Lake
chert 3072 2472 1680 1392
1512 2016 1392 55


Removed from Hot Oven

Obsidian 1123 1104


Johnson Lake
chert 5072 1344 1152 63

aRate of load was approximately 2000 lb/mmn.

bThe results are not consistent.

CIt is difficult to explain this anomaly with what otherwise appears to be a significant difference.





71
strength which occurs when specimens are removed immediately from the hot oven is due to stresses resulting when the material is exposed too rapidly to a cool environment.


X-Ray Diffraction Pattern

Twenty-six x-ray diffraction patterns were run on

13 different samples of heated and unheated charts. No consistent differences could be detected indicating that no change in the crystal lattice occurs (see Figure 14). The slight difference shown is well within the range of experimental error. If the crystals were coarser, the peak would be higher; if the crystals were finer, the peak would be lower.


Differential Thermal Analysis (DTA)

The method of studying materials by differential

thermal analysis consists of heating a small, finelyground sample at a constant and rapid rate, and recording by suitable means the endothermic and exothermic effects. A differential thermocouple is used to detect these effects. One of the thermocouple junctions is placed in the sample being studied and the other is set in a thermally inert substance that is undergoing the same heat treatment as the sample (Berkelhamer 1944). The electric current generated by the differential thermocouple is amplified and recorded. Endothermic peaks result if the sample is taking on energy.

Samples were prepared of pure quartz, pure opal,

heated and unheated Johnson Lake chert, High Springs chert,




























ii I- \ I - --Heated Chart




12








22
iae














Figure 14.--X-Ray Diffraction Pattern Illustrating that No Change Occurs in the Crystal Lattice when Florida Cherts Are Subjected to Critical Temperatures.





73
Ocala chert, English flint, and obsidian. Arrangements were made with the Soils Department at the University of Florida to use the differential thermal analysis equipment. The results of this experiment were encouraging since they substantiated data obtained from the weight loss experiment. As the sample takes on energy (heat), water is driven off. This was apparent by the endothermic peaks at 11200 as shown in Figure 15 for opal, Johnson Lake chert not previously heated, Ocala chert, and English flint. This was due to the removal of the adsorbed water held on the surfaces of the microcrystals. In the pure quartz sample, the already heated chert sample, the High Springs chert sample, and obsidian there is no peak at 11200. These materials have already been devolatilized or there is no moisture to drive off. The only anomaly that seems to exist is that the chert from High Springs which is Oligocene in age did not show a peak at 112*C. This material is more coarsely crystalline than much of other Florida material. This fact is borne out by the quartz peak at 573*C occurring with this sample and the pure quartz sample. This peak represents the alpha-beta change in the crystal lattice, and it is immediate as the sharp peak indicates. This inversion reaction is reversible in heating and cooling.

To check the validity of the endothermic trend beginning about 3500C-400*C (see Figure 15), additional samples were prepared and tested as before. These materials were rerun to determine if the endothermic trend indicating an






Quartz, Pure


Opal, Pure


//


Chert, Johnson


Lake Preheated


'3


Chert, Highi Springs, Oligccene
4


Flint, English Chert, Oc aa


Obsidian


3b0
Degrees Centigrade


.


Figure 15.--Results of Differential Thermal Analysis


100


200


400o


500


600


Quartz, Pure _


Lake


. . . . . . . . .


Chert, Johnson


c . . . ,.


.,





75
increase in energy being absorbed may have been due to an instrumental error. Except for the absence of the peak at 112*C, the rerun materials exhibited the same type of curves as were initially observed. The sensitivity of the recording galvanometer of the Soils Department had been adjusted for the detection of the characteristic peaks of minerals whose thermal reactions are of greater magnitude. Thus, within the framework of tests available to this experiment, the curves seem valid.


Petrographic Analysis

A total of 45 petrographic sections were ground to approximately 1N to show the internal structures of chert, especially grain size and orientation, intergranular relationships, and cracks. A careful search of the slides at a magnification of 10OX to detect evidence of differences between heated and unheated specimens failed to reveal anything significant. Some of the slides suggested that heated materials had more fractures which were more open and more oriented. Due to the heterogeneity of chert, however, it is hazardous to draw any conclusions from the petrographic study other than the fact that there is no change in size of the individual crystals or their orientation when charts are heated to temperatures of 350*C-400*C. This statement is in agreement with the findings of Tullis (1970: 1344) who reports that Dover flint even when subjected to axial compression revealed no preferred orientation when loaded at 4000C under a differential stress of 3 kb for 20 minutes.





76
Three additional slides of Johnson Lake chert were ground to N~, which is standard petrographic thickness, to determine if thermal stresses could be detected which may have been generated within the grain by the application of heat. At a magnification of 430X no differences were observed for an unheated control, a specimen heated to LI.OC and allowed to cool in the oven, and a specimen heated to 4000C and removed immediately from the oven to a cool environment (see Figure 16). Thus, despite the fact that strength tests revealed a significant reduction or increase in strength between heated and unheated cherts, and that point tensile tests indicated there is an even greater reduction if materials are removed immediately from a hot oven, these changes are not observable petrographically.

Determination of Specific Surface Area

The method involved in determining the surface area consisted of the gas absorption technique in which helium is used. The data i'ere analyzed by an Orr Surf ace-Area PoreVolume Analyzer. Four samples were submitted: High Springs Oligocene chert which is coarse grained and gave a quartz inversion peak on differential thermal analysis, Johnson Lake Eocene chert which is fine grained, and Eocene chert from north of Ocala--both heated and unheated. The results of the tests on the unheated cherts were consistent with their grain size and packing. The least specific surface area was

4.64 MN2/g for the High Springs chert; 5.39 M 2 /g for the Johnson Lake chert; and 4.86 M 2/g for the Eocene chert






























unheated


heated

Figure 16.--Petrographic Sections Showing No Detectable Change in Heated vs Unheated Florida Chert (Scale: 1 inch = 1,500,000 k).





78
from Ocala whose grain size is intermediate of the three samples. Most significantly, the Eocene chert from Ocala that had been heated showed a marked reduction in the granular surface area: 1.90 2 /g compared to 4.86 M 2/g for its unheated counterpart. This represents approximately a 60% reduction in the granular surface area of the heated chert. There is no question but that the microcrystalline surface area has been reduced in the heated specimen. This was due to the reduction of the intergranular pore radii. In other words, porosity had been decreased due to a fusion or intergrowth of the grains.

A computer printout showed the size of the pore

space distribution and surface area distribution relative to percentage of occurrence. The plot for Ocala unheated chert showed the minute size of the original pores: 27.81% of the pores were 23 � or smaller in size whereas about .14% were 370.84.


Scanning Electron M~icroscope

The scanning electron microscope (SEM) is used to study surface morphology (Krinsley and Margolis 1968). Small flakes not exceeding 1/8 x 1/2 inch were pressed from unheated and heated cherts. The samples were cleaned with acetone and mounted with Scotch tape on an SEN specimen plug. Three or four specimens were mounted on each plug. The freshly fractured surfaces were exposed for scanning. The specimens were then coated with gold "in order to make the surfaces a better conductor for the





79
electron beam; the technique does not eliminate or create any additional surface features" (Krinsley and Miargolis 1968: 458). Heated and unheated samples included silicified coral, Ocala chert, High Springs chert, and fine and coarse grained Johnson Lake chert. The specimens were placed in a Cambridge Stereoscan electron microscope housed in the Department of Metallurgy on the University of Florida Campus. The entire fractured surface of each of these specimens was scanned. Figures 17 and 18 show the typical surface topography, dramatically illustrating the changes which occur when cherts are heated. Figure 17 is of Johnson Lake chert (lOQOX); Figure 18 is of silicified coral (12,200X). In the unheated specimens, the individual grains are seen looking like so many bread crumbs. Some fracturing has occurred through the individual grains but more frequently

the fracture goes around the grains. In the heated specimens, the fractures pass through most of the individual grains; that is, the individual grains are actually split, and the fractures continue on passing through the interstitial areas which are now more firmly cemented. In other words, when fracture occurs it alternately splits and passes through succeeding crystals and intercrystal areas in its path until it terminates. This accounts for the smooth surface in the heated specimens.




80























unheated




















heated Figure 17.--Surface Topography of Unheated and Heated Johnson Lake Chert Samples as Viewed by the Scanning Electron Iicroscope (Scale: 1 inch = 254,000 1).































unheated


heated


Figure 18.--Surface Topography of Unheated and Heated Silicif'ied Coral from Florida as Viewed by the Scanning Electron Microscope (Scale: 1 inch 20,320 Xi).












ARCHAEOLOGICAL APPLICATION


If an archaeologist suspects that the chipped stone remains he recovers from a site have been thermally altered, it would be desirable to subject these materials to a standardized test in order to eliminate the "guess" factor. This is important since thermal alteration present.information concerning not only stone technology, but contributes ultimately to a greater understanding of prehistoric man's behavioral patterns. This becomes even more valuable if an investigator is working on time levels where only stone artifacts have been preserved.

The following discussion involves a review of the many experiments conducted throughout the course of this study to determine if one or more of these might feasibly be applied to site materials. For a fuller account of these experiments, the reader is advised to refer to the section on Methodology.

Weight loss cannot be used as a criterion to

determine if specimens had been thermally altered because experiments demonstrated that heated specimens tended to take on moisture again. In other words, if an archaeologist weighed, heated, and reweighed outcrop materials along with site materials to check differences in weight loss he probably would find no significant difference. And even if 82





83
he did, he would have to use the results very cautiously since he could not be absolutely sure that his site material was identical with the outcrop material. Chert will vary considerably even within the same nodule. Differential thermal analysis probably would also reflect this tendency of the material to take on moisture.

If stone remains are found with "potlid" fractures or fractures minus bulbs of percussion, it may be said that the stone had been fractured due to expansion or contraction resulting from heat, but there would be no sure way of determining if the exposure to the heat had been intentional or because of a forest fire or hearth situation.

Standard rock mechanics tests might be of value to test site specimens with outcrop materialsbut it probably would be impossible to recover large enough specimens from sites to prepare samples whose dimensions must be precisely accurate in order to assure the validity of the results. Thus, this method succeeds in theory but fails in practical

application.

Petrographic analysis revealed no change in the

size, shape, or orientation of the individual microcrystals. This was borne out by the x-ray diffraction pattern which showed no change in the crystal lattice between heated and unheated materials.

The vitreousness of a surface that has been flaked subsequent to thermal alteration offers, perhaps, the most valid indication that this method has been employed.





84
Vitreousness may not be completely reliable, however. Several broken specimens were selected from preceramic levels (>2000 BC) of a site (A-356) in Florida. These specimens were chosen because their outer surfaces were extremely lustrous and some exhibited a pinkish cast. It was suspected that all had been thermally altered. Small flakes were pressed from each specimen. One specimen which had an especially greasy luster on its outer surface was very difficult to flake and the freshly flaked surface was dull. This was a disappointing development, because it was hoped that by removing chips from field specimens, it might be determined that vitrification which penetrated the entire mass of test materials is a permanent change and might be useful for archaeological interpretation especially if local outcrop materials are not naturally vitreous. This specimen had either patinated subsequent to thermal alteration resulting in a replacement of the internal luster, or soil conditions due to long burial had operated to form the greasy luster on the outer surface. The former explanation is more plausible because often materials that are not lustrous will be recovered from the same location as lustrous materials. If soil conditions were responsible for the luster, then all specimens should be affected.

In examining a representative sample of flaking debris or artifacts that are suspected of being altered, an investigator should find a number of specimens which exhibit a relict dull area surrounded by extreme vitreousness. This situation suggests that the dull area has not





85
been flaked subsequent to heating whereas the vitreous area has been (see Figure 19). Soil conditions would not produce this type of differential preservation.

Color change which occurs at a lower temperature than the significant change resulting in a greater ease in flaking, may be considered a reliable indication if accompanied by vitreousness.

One other suggestion is appropriate. If local

outcrop materials differ in texture from site specimens, it is a simple task to heat the local materials, fracture them, and determine if the resulting surface resembles site materials. This is how Mr. Crabtree first suspected the thermal method had been employed (see Literature Review).





















CO















Figure 19.--Specimens from the University of Florida
Collections ShowinG Dull Areas Not Flaked Subsequent to Thermal Alteration Surrounded by Extreme Vitreousness in Areas that Have Been Flaked after Alteration.












SUMMARY AND INTERPRETATION


Despite derogatory comments by experimenters who

have "Proved" that subjecting flint to fire has only destructive effects (e.g., Pond 1930; Ellis 1940), enough firsthand accounts exist (e.g., Schumacher 1877; Powers 1877; Man 1883) to warrant investigation of the technique.

Extensive experiments conducted throughout a twoyear periodic which flint materials were exposed to heat under numerous diverse conditions, have demonstrated that the alteration of siliceous rocks, when critical temperatures are reached slowly and maintained for a sustained period, probably conferred an advantage to prehistoric man in manufacturing his chipped stone implements.

The oft-quoted method of dripping cold water on hot rocks has been largely responsible for discrediting fire as a contributing factor in flintworking technology. Attempts by this investigator to "chip" with cold water produced no flakes at all and resulted in a crazing of the rock thus confirming the findings of Pond (1930) and Ellis (1940). However, if one returns to the reports of Schumacher (1877), Powers (1877), and Man (1883),,they report removal of rocks from a hot fire after which they are shaped into implements. The only objection to these accounts is their brevity. A more detailed description or closer observation 87





88
by those authors may have revealed that the stones were not subjected to an open fire, that they may have been buried, or that they may have been allowed to remain in the heating environment for an extended period of time. My investigations have shown that:

1. Materials removed from a hot oven did not fracture when exposed immediately to a cool environment if the temperature necessary to effect an alteration in the rock had been reached slowly and maintained for a long enough period for the process to be completed.

2. Under point tensile load, a greater reduction in strength occurs when the rock materials are removed immediately from a hot oven to a cool environment. Limited tests gave results as follows: materials heated to 350*C but allowed to cool in the oven had a 40% loss in strength over the unheated control. A sample from the same nodule which had been heated to 350*C and exposed immediately to a cool environment had a 63% loss in strength--an additional reduction of 23%. It is possible that for certain extremely inelastic rock types exposure to these increased stresses was desirable to make chipping easier.

The accounts of the above-mentioned reporters are probably accurate as far as they go. Their descriptions, perhaps, have been misinterpreted more because they are incomplete rather than incorrect.

Another objection which might be raised with regard to primitive man's heating of rocks would be that since he had no thermometer, he had no way of knowing how high the





89
temperature was. This would be almost as ridiculous as saying that he had no conception of time because he hadn't invented the watch. Besides, these investigations demonstrated that, at least for Florida cherts, temperatures between 350*C and 60000 (a range of' approximately 5000F) would effect a desirable alteration in the material. That is, as long as the elevation of temperature was gradual, there was no increased ease of chipping at 60000 over that of 5500C. While there is no apparent increase in flaking ease, however, quite often attempts to chip flint materials that had been heated to 500'C-600*C or had been heated to 350*C-400*C and removed immediately from the hot oven, resulted in a lateral snap due to end shock. Thus, there is additional strength loss with increased temperatures or increased stress. This fact was supported by point tensile strength tests. Below 30000 a satisfactory change did not occur in Florida cherts. Materials were not tested above 60000 (approximately 1100*F) because the aborigines probably could not reach or sustain such high temperatures.

It remains to determine if the three major problems to be investigated in this study have been successfully solved.

1. A desirable change does occur when Florida cherts are thermally altered resulting in a stone that is easier to flake than its unheated counterpart. No structural change occurs in that the size, shape, and orientation of the individual microcrystals remain the same, but through the removal of interstitial water, the microcrystals are fitted




Full Text
Figure 5.Results of Experiment Conducted to Test the Validity of "Flaking"
Hot Stones by Dripping Cold Water on Them: (a) The Rock Literally Fell Apart when
Flaking Was Attempted (note deviation from conchoidal fracture typical of flint
materials); (b) Magnified Area Illustrating the Crazing which Occurred.


5
Sc huj ac 5 .: r co o i t o t to.
Tro rock is first exposed to i.i .. ftc r a
thorough heatin~, ivpivly c>: u.lc6. of', vT: in f l r /.r,
r o ad i 1 y in t o 3 he rd o of d .1 fit. non t s i -- o s u? > J e r v;e 3. ?>
dime t ed kiowa at i hs c.1 o\ v;v o (1 c7r,:: l'Ar/)
Powc rs a o c c i c' ;> !} t- f o^ 1 ox1 :i n>
It v.-ac a ocurce of vonc! _r cu no hov; the in.t:n>.te
ar r ov?~3ie aas \ise1 on r ariv/s vi tk f:e-] ^ oa-v u.ir.*
pointe could he m;ce rifhou:; b r;; c kin:, the.-, to pieces.
The V ianci l : ;iy a j o f u o .i t ? .rn Gal ?. f o -,:nu j -oc a ,7 in
the fc 11 ov;in j :.a nun r: T v); :ln y a p- i o e c o f ? s r t c he- rv ,
co g i di an c r c c; - f.1 :i n . v.i to o b v c >; s aha vs-eo>: e re d
and vi t h a c or> c ho i 0r; a i"r ? c Lx u r e t-h op he at i + 1 r- t ho
f i re pi id tii era c o r-.l i t a 1 c-v 1 y, vtJ cii at; 1 i t a .11 j n
flakes (1877 1C>>*
Other authors (cvy* has on 18c. 7= P?6; *ov;kc 1896:
17P) rafe-r to the Po./er^ ano S chuna chon accounts hut aoo
nothing pertinent. The set hods a escribed by rover's sn^
SchXi'iackox' ore iro?:. plausible than those svov;irp th-it r-.rroi.'-'
bends i.re lace by dr?vein-; eoZ-\ ;afcer on liot stones; ho*-;~
over, if she-.;Id >'o poh.xted out that, they are in the aiircrity,
T'o e aovo no fe *- one c. s c on s t i11:.te the t ot al ity o f the
an? v. 1 ah 3 in i o v. -u\ t: c a or- t his s no ,j a e t v/ f h re r a rd t o / jlic r ic -:-.n
In.d? en piv.olic e s c.] o -¡s oy-A d i.*-e ovo re 0. s oi .'.reo ef a.
The author is hi li'Vi'K-ivc correspondence v/iti; ii.or.reth i.-
Oihlsy of fho DritMv: i'/esom.-; .- or.tcn. Re v;as not avaro of
this teebrique at .*!! :-av! could not 're''all r-_eui.nr any
. v. c o i >r i; of any ne o; in -ic a-1:- i r i r r f :*.. o b s f o ro f i ?n sh' n <, is i
p r o o c t lie -p o in b f o .7' (i: ? hi-;; 1K 30 <, vers on cl e o u c un i c a fc i on ) .
/.-lottor Sure ; o cr. f c ; o ?. or, 3J'r ;. r: *rrc rci u-¡
<. j au; l: c-J o,i f i 1 L, r,ri. o b v -. c i;.y sone flint an d
th-n ho tere, c ;ie i n uov tr thermal txu.pt:- -J.ii; bu;-.h t,v "...,! u... -c*;. i [ sec- ~ c r\ir- 3 j.968;
159J cud both :./ i fj.'--icv h .ve dor ."h. .v i/i -:o.rk
on o s ut: 1 'vh, .-e( C root .re o 1 v 6 V A r j re on .t .1
coumuiico t j.on j.


Figure 13.Composite Illustration of: (a) Compressive Strength
Testing Machine, (b) Close Up of Jig with Core in Position, and (c) Core
Split by Application of Point Tensile Load.


6
Many excellent accounts exist of aboriginal stone
working techniques. In addition, numerous experimental
studies have been conducted and reported upon which describe
the step by step manufacture of tools by direct percussion,
indirect percussion, pressure, and various combinations of
these methods. These techniques constituted the major
processes employed in shaping and finishing stone tools.
The author does not wish to give the impression that it was
always necessary to thermally alter lithic materials. Some
materials probably needed no alteration. Nor is it felt
that fire was used in shaping. But it is thought that fire
often played an important role in making the mechanical
processes less difficult during some stage of manufacture
prior to final retouch.
Holmes (1919) compiled a summary volume entitled
Aboriginal American Antiquities, the sources for which are
nearly all pre-twentieth century as a perusal of the bibliog
raphy indicates. This book served as a springboard to the
past since Chapter XXXV is entitled "Fire Fracture Process"
and contains a number of useful references; those of which
were available, in turn, led to others. Many of these early
publications were not available. Despite the fact that com
plete coverage was not possible, it soon became apparent
that man's use of fire in connection with his chipped stone
tool-making technology fell into three main categories:
(1) exposure of flint to fire as an aid in the chipping
process, (2) use of fire in quarrying operations, (3) caches.


of jgk-'aal
AO A AF '.!A" :jJ A,
LIST CT il-ABLJA ............
LIST *.- jUISo
ABSTRACT
TNT. cO liJ 0 IT ON ............. .
LITSiiAH'.-.F l.JOIOF
xpoeurs of flint to fire os At
Chin'S lOoooo' .
re of Tiro ir. 0,o: o CpszaUio.;:
Cachn
13CO.. of.f% t .A .. :.. f. A ... ..
T. SI' v jGACG "i
Headnf; S:aie."Ho;i., .......
V:eir;ht Lose ..........
Decrepitation as Sp] ... .
Viwcour.ot8 .
L5.30USS5 oji" ..........
Iron Son: ni of i'joria' A oj/F .
Strc-r.'t'.- Ad;,f . AO. .
cO'ffilB tioj cf the 3Si or
opjgj : '.A on-. .FA . .
I-oi:)! Tor .-4r' FA sir .......
X-Ki*!fc'il§f|SEg.C':F A".tcr..-n .
Dif&trc.r r.A J. ftafljHB j, (JT..;
Vo "*pM ,, ri.j ......
DoF:..' AiAr of n a: .Ad: '"a ,F
FA. FFoet A.FoBj.-o.:H ,
v
viii
I
1C
is
j 5
is
AC
A, J
V/
ho
59
60
OF.
71
71
r*;r.
7¡3
Ff
BI-.LIiAO
93


2
altered. The number might be greatly increased if it were
known whether patinated specimens or specimens recovered
from under the water had been subjected to heat. Patination
as well as minerals present in Florida lakes, rivers, and
springs cause changes which conceal the original texture of
chert, making it impossible to determine (at present) if
thermal alteration has taken place.
The objectives of the research then undertaken
were:
1. To establish whether a functionally desirable
change in the chert occurs when it is thermally altered.
The e2q>eriments conducted are described in the section on
Methodology which embodies the major portion of this dis
sertation.
2. To demonstrate whether prehistoric peoples might
have been aware of the advantages conferred by thermally
altering their lithic materials. To aid in this endeavor,
an intensive and extensive search of existing publications
was undertaken. The results of this search are described
in the Literature Review.
The use of analogy in interpreting archaeological
data "In its most general sense ... is assaying any belief
about nonobserved behavior by referral to observed behavior
which is thought to be relevant" (Ascher 1961: 317) Un
fortunately, historic accounts were not found which accurately
described the process of thermal alteration. However, enough
descriptions of the use of fire during some stag of stone
tool manufacture were uncovered to warrant the conclusion


tre vitr.ou..
S5
been flahed ,mbs: quon t to hcc.tin;. v.hero;.
area has be on (see Figure 19)* 3 oil c or,d ill or g v< c u 1 d not
produce this typo of differential presentation.
0 o 3 o r ehr'^ ;;e d' J c h c o cv. re rt .? 1 o ; o r t cue er a tur e
then the significant change re cult in ip in a greater eo.se
j.u flahiny, nay be considered a reliable ;ndication if
a e c os j c,1 n i e cl t y vi t: c o us n ess,
C n e o t he r si; yy cation is app r op i :i a 1: e I f loco 1
outcrop materials diffex* in texture from cite spcciriens,
i t i s a. o ii i 3 e t a ok to heat the local mate r i o 1 s, frac tur a
the1. j and doter¡ ine if the rosultiny sarface resenbj es
a it. in o t o r :i. a 3. s, I'll s is ho v: Kr, Crabtree fix c t r uspec ted
the themal jr.ethod had been employed (see Literature
he via.)*


1.13J* OF IIO-a.o
1. /real Distribution o' Outc.'Ope Frobcbiy Ccrt-aininf,
Chert in Peninsula:' Florada 2.1
2. VP igat. Lobo upon Festine: Chorea irosa Various
Locations i Florida ?S
2. Weight J/>so o.' Samples < f Florida Chart IIlustrctiug
the 'i/pical Pattern Chservoi for All Florid-
Speciffie-na ioc-tel Throughout a Iwo-Ieoi- Period .. .
4. Explosion Seoul ting from Poo .sapid Exposure to Heat J5
5. Results of Cmrrrirenf Conducted to Teat the Validity
o: "i-laXir:;'1 Hot Stones by Orio^ing Gold l/etar
on -Phea y:i
6. Yitroeiu-j'.DuS Occurring when Florida Chente Are
Heated and iub.aecuonvj.y FlaRef. ..........
r/. Example of a Potiid J'rr.ctnre vbicfc Cites- Oommu-red
when Florida Cherts Wore Subjected too i .
to 400* 0 Tersvser.-. buree
3, Examples of a. "Cronatod" Frac toja: wMoh Often
Occurred ebon Spectre"-:: Ware :-x>5.ovec Directly from
a Hot Oven to r. Cool Environment z/
Specifier. Domictin; Tntcnticnnl Fracture vsith Bulb
of I'crcussicn an* iypio-aj Fractured Surface
Empi-asismcr-j that I*ipycl Bss Occurred ....... .36
10. Heato.: Cpacir^ene and Unhealed Control.: Ill us crating
ite-iree of Color Change Do pending uven the Air-our.t
of Iron Presort in the Chert
11. Coi-pote Illc.at::"'t:ion of: (a) Drill Iroso,
(b) Corcroatio. i.-.¡..on Co.e Bit, ar.c (o) a Chert
Kofulc with Color Rencvt-d to Be lire-l for
Strength cete, 61
1?. De creamj or Incese in Compress iv:- Strength over
Urlee -t.i'd Controle of Hooted o..cc :il .r (A
15. Coapfisitr? Illustration of; (a) Compressive Strength
lint'..', 1 (b' Clore Up of ,A>.- with Core in
Pon tic.ii, (o'. Dm re relit b; - 'l 1.; alien of
Point IV.'ir.! 1 o Load.


TABLE 10
RESULTS
OF POINT
TENSILE STRI
NGTH TESTS
a
Sample
Unheated
Control
300C
350 C
400 C
Total Strength
Loss
(%)
Allowed to Cool in Oven
Obsidian
1872
2640
1536
2232
u
1944
1416
1368
D
High Springs
chert
2568
2448
2136
1584
1680
39
Johnson Lake
chert
3072
2472
1680
1392
1512
2016
1392
55
Removed
from Hot Oven
Obsidian
1123
1104
2670
Johnson Lake
chert
3072
1344
1152
63
Q
Rate of load was approximately 2000 lb/min.
The results are not consistent.
c
It is difficult to explain this anomaly with what otherwise appears to
foe a significant difference.
o


:-f V i-.;
corox throughout the entire h.-.- -il.noof x or and
? Ktrel.c.1y 1 ; :>-1 ? \ a a.d bo. ';;. ncur* *'* o a11;- J:o\*cvgr ,
tac chert is found in thick roaniad nodu1: s ov boc.s and
the fine grained orea under the cor tor rapidly shades in ,o
c> coarser g is lined area farther v;.*.thia hoc oss., The reason
f or t fc i s di t1re no c r. t o :< ture i s uo t o 1 c. r bu t i f o cc v.r o
dur-:ra roo3 c v-'.vent of the hi'.echo-no by si3 i r :. and night
bo "due to a esc?, easing rat j of px*oc.:- pitation because of
the diuini shire rete of supply of solution as cons cl id
'L. i O. J. p r oo o d s '* ( To 1 h and We ave r j 9 p? : ;;00-1;
The Eiial .1 sr Inc si z e c f line c ryp tocry a t a 1 st he
Ejc/.*fv v he : -.o t c ri -a 1 w 13.1 exVi itt t 'i e \ i cr o o o.s 1 u s t c r w f pi ;. u :
on a frac tu re d sur f ac e > and tt\ c c ? i r- r n sc, the 3. o r. ~e r t k
ci-votcv:ryetc-3s, the .Less 1 ustrc s ias the aygregatc uasa :.'j
appear .0:00. Interestingly, after coarse groined aborts
pt-s heated slowly to around J?OuG, left for a period of
ti v -rii subsoq'ently fra c ture d the fr& ct urod surf .vc c
a >:'-> i.t: ... f_,3 c s -2 i k _ 1 u a ter bu t the grain ai e h a o n:-1
boon cho.vje-:., The reasons for this ore quito sin a le and
. .el J 3 : e v: ^ c V in t; :d:,c :, s i; o whi ch x o i 1 ov?s, ifr 1 o G
f.'.v izes '- -: !- lrr.; 1.1. ocupl-.* of
c'u.-j i*> ; v-j- J1 i ferent rcck a':.os ar;,} 3.os -r ion:.. 3 ho: *-:
ic-r. i-s we:."2 o undue tod to cl a tor ;ino the 3,c-<.i..;th of tia-v r.
s ay to i fe c ;; j. to :¡ *a o iu s
i1 tur^c urf icc, lacn L,o o,p c sor. i cs }.o.ar; -d ; | cach
toi!; o v ; tu r-c I: h t to 1r r.'3 and 3 cv i <1 j.- ?. hours aft vr
vf = icPi hi:/ *. or is io<. d 301 3 ip:i -.r. j¡! ¡ f oi 3.-hr'u?* pai-*:?d


77
unheated
heated
Figure 16.Petrographic Sections
Showing No Detectable Change in Heated vs
Unheated Florida Chert (Scale: 1 inch =
1,500,000 a).


20
to the replacement of carbonates with silicas* All of the
chert deposits in Florida are in relationship to relict clay
hills in contact with limestone; these generally correspond
to the Ocala Arch where siliceous deposits lie unconform-
ably over the Ocala Limestone. Cherts also occur at the
edge of the arch where limestones are interbedded with
siliceous deposits. The occurrence of cherts is thus in the
upper part of the Eocene Ocala Limestone, and the Oligocene
and Lower Miocene Formations bordering the areas of the
Ocala Uplift. Cherts found on the Ocala Arch have replaced
limestones that are Eocene in age and those such as occur in
Hernando and Hillsboro Counties have replaced limestones
that are Oligocene and Lower Miocene in age. Cherts in the
Miocene deposits are found as far south as Zulpho Springs,
Hardee County. There are no cherts naturally outcropping
along the east coast of Florida or in south Florida (Brooks,
personal communication). Figure 1 shows the extent of the
areal distribution of formations that might contain chert
in peninsular Florida.


41
cortex throughout the entire thickness of the rock and is
extremely glass-like and homogeneous. Typically, however,
the chert is found in thick rounded nodules or beds and
the fine grained area under the cortex rapidly shades into
a coarser grained area farther within the mass. The reason
for this difference in texture is not clear but it occurs
during replacement of the limestone by silica and might
be "due to a descreasing rate of precipitation because of
the diminishing rate of supply of solution as consolida
tion proceeds" (Folk and Weaver 1952: 500-1).
The smaller the size of the cryptocrystals, the
more the material will exhibit the vitreous luster of glass
on a fractured surface, and by contrast, the larger the
cryptocrystals, the less lustrous is the aggregate mass in
appearance. Interestingly, after coarse grained cherts
are heated slowly to around 350C, left for a period of
time, and subsequently fractured, the fractured surface
exhibits a glass-like luster but the grain size has not
been changed. The reasons for this are quite simple and
will be explained in the discussion which follows. Table 6
summarises experiments using large and small samples of
cherts from different rock masses and locations. These
tests were conducted to determine the length of time neces
sary to effect alteration which results In a vitreous
fractured surface. Each group of samples heated at each
temperature was taken to 100C and left for 2 hours after
which they were raised by 50C increments for 1-hour periods


83
he did, he would have to use the results very cautiously
since he could not be absolutely sure that his site material
was identical with the outcrop material. Chert will vary
considerably even within the same nodule. Differential
thermal analysis probably would also reflect this tendency
of the material to take on moisture.
If stone remains are found with 'potlid" fractures
or fractures minus bulbs of percussion, it may be said that
the stone had been fractured due to expansion or contraction
resulting from heat, but there would be no sure way of
determining if the exposure to the heat had been intentional
or because of a forest fire or hearth situation.
Standard rock mechanics tests might be of value to
test site specimens with outcrop materials, but it probably
would be impossible to recover large enough specimens from
sites to prepare samples whose dimensions must be precisely
accurate in order to assure the validity of the results.
Thus, this method succeeds in theory but fails in practical
application.
Petrographic analysis revealed no change in the
size, shape, or orientation of the individual microcrystals.
This was borne out by the x-ray diffraction pattern which
showed no change in the crystal lattice between heated and
unheated materials.
The vitreousness of a surface that has been flaked
subsequent to thermal alteration offers, perhaps, the most
valid indication that this method has been employed.


Figure 4.Explosion Resulting from Too Rapid Exposure to
Heat (note "potlids" and blocky angular flakes).


air g-t?


ACftlTOVLSDO 31. .j
TU is study could not Love- b: under
c e a c fu3 1 y c cl jp 1 r. to d v i t i o ub t he co op o: t i o of. y y o:: 3
v/.i t h v ir y i r r; scion t i fio b ac r;;.r-cun d s v; h c c Lr ii i .h. b .' -' r
hnc/Iedge, fine, and cqiilpiaen t. f his i,yye of :> n bex Jisci-
pi in cry approach is increasingly iiiuoros'Vi as ^iocdi^';-
txon bg c one g a noco s city in a.: ix frsic3.y c o iiv 3.o-o id .
TU o a u t ho r v i sh e s t c o xp r a s u appr eel a b i on o 1 o
])opnr indent o Ketallur^j fo: oshliv it possible to u 1:
Sc roxx in y 11 e c t ron K ic roo c o y o \ t he C1 v 11 hi ip x n o r jo:y y- 1 r t
i..on t f o i: tb ue o.f t ho i r e qv i y.*. u n i o:.- A f o;o as s i s v .: 1>':
tU o ro c-3a jae eh *jnic s t e s t s: the 3 o i 1 a I :*y . r r;.. o nv f'c ; "-. o
o l t ho i r evs ns fox a sois tiny; i rifo di foe ro n t i 1 b r
an. 0.1 y 3:1 s ond f cr cond uc:: iny: tie. ui -.a e apebrc r-o c- b. .
i.1 y s i s ; t c 1 e oi o v j Zop. ar f r a t f c_ o. o i r: ;: n;, ri.! . o t.
gr a: > ho c x > \ a y s i .
0 010 r.isxna fr-n c f
surf of. 0
C f- W 0 :: i. ;, c t r: j? t s .
, 1 fox nor six to
'h; ft! t o
c< 0 a ; I; i'i e 0 rb r 11 s
of cry Supervisor:.
...u
iJr. C*: >. rl o.... Vs i rb an-;;3 for s\up;;;o s biny n
these Arvve c ti .11i cis an.d for od 11r< 1 ial ar1
aro .-..c-.d a.-J.
010 : 0 j f i eir
too j r ; a ? \
a j svprcvii.;- 00
istanco,
Til; re re al v ;/ c 3 o o o 01 nor.; 1 c j. l l 1 on 0 vb 0 ;::
port r.; C -i,.. :.: : i:n do r *; 0 m 1; t "if. d c c o> 1 .* 0 i :; r 0 1
t ;. c ;<' c t s o v 0 r ,. c 1; 0 v 1. .0J : v di i i ; a 0101 10
£yn. f'jful tc ; I: *- V>;- --r c V : > b-.- v.
x


52
differently when heated were submitted to the Soils Depart
ment at the University of Florida for Atomic Absorption
Spectrophotometer analysis. The results of this analysis
are given in Table 7. It is not known what percentage of
calcium is necessary to prevent the desired reaction but
it is interesting to note that Ocala chert and High Springs
chert had considerably higher percentages of calcium than
the two Johnson Lake specimens. The Ocala and High Springs
cherts consistently reacted differently than Johnson Lake
and other Florida materials tested in that the expected
change did not occur within the same temperature and time
ranges.
Figures 7? 8, and 9 illustrate various types of
fractures. Figure 7 shows an example of a potlid fracture
which occurred only when the materials were heated too
rapidly. Figure 8 shows the type of fractured surface
which often occurred when the samples were removed from a
hot oven to a cool environment. The specimens in Figures 7
and 8 have broken with a conchoidal fracture typical of
flint materials. Figure 9 is a thinning flake, intention
ally struck from an obsidian core. In addition to the
conchoidal fracture, this last specimen possesses a well-
defined bulb of percussion not present in Figures 7 and 8.
Figure 9 serves as a reminder that a microcystalline rock
will break with a conchoidal fracture but no bulb of per
cussion will be evident unless impact has taken place.
The results of the heating experiments establish
quite clearly that crystal boundaries may be a disturbing


81
unheated
heated
Figure 18.Surface Topography of Unheated
and Heated Silicified Coral from Florida as Viewed
hy the Scanning Electron Kicroscope (Scale: 1 inch =
20,520 l).


50
load* In. addition, while there is no apparent incr> a
flaking sr.^e, quite often attempt': o e/iip flint materiel
that had boon heated to ^00oG--600''f on had been heated to
3 50 3 C 40 C an d removed imr.e d i & t c 1 y f r c 1: l he hot 0 v 1 11, re
sulted in a lateral snap due to end ehovu. iris tree ture
did not occur at the point of impact* fee f.r iciir : ' our-
fac often resenbles that i 11 ustv?; fe<3 in ill3i¡v <' 1 i in l-
k '.uipp o r s are £ ami 1 i e.r v; i t h j> i s t ,/p o of f a i 1 ur s 0 '<. .; r iJ:
occurs when a substantial bio*.; is imparted to o. roca r'- u.u
mass is not adequate!? y suppe ted to absorb the ebook, V.; '
these heated nalorielo, hov'ever, iriiure occurred i/hon re!
slight pressure or porous3ion //as apelieu.
jy.; e c c.i positic e o f t V a c her1 i a a 11;/ b o und we .10 r in a;/
71 o i be i dsr. t i ca 1 t o w1. 10r as ;/ o no rnu I1 y ih ini; o i *c r. 1 .nr
i 3 1 o0 < ..[ i t h e hy d myo u an. d o >.y j en i c ns a re d i r a c c \ a 1 a d
and the oxygon pluo parr of the hydrogen are fiver off
when 7 contain torcer." ture '"s reached, the remar nin;; hycrof
;l :u i \: i :> t y o o :l t v a c h err e me y h 00k up v; i th t ho 00q at i \ j. ,
cha.Ljei c:--.-r '!utinff 0:C the iJcrocresta 1 and scrye as the
\:.! ; d a r. Or i f the d e e \v 3 s c cl u 11 i 0 c:; ?. on i a s e. ;i a t r , i c
y.onV r u l;h uo -t y-ym 5 cu fno vn "- J 'r ui:0 ml decrypt
v v.., .. .... h'-e bond in that vuqe
1 c: 3 slur i r. d ... s';: r or (19 r f ; : f tv.- o u r.q :;. u t i cy- \-
t: " ci. y / 0 v u0 ; t :* o,':: o i* va v i.: vc t 1 u ef' iu . r , f 0r:
; >. ... .. i .. -v 1: -,s j t j c i r > c o o o v r : * '* ; > o:iT i ] y i; 1 U; 1 f 171L a
i nt d i:e tv .. ci r . . i ; " \>- f r-,/ but 11 .y iiol^ .*.-o?;.3 c.ppl 1c:i ¡lo
.rs.ee i;c- ;.ei.. Luios of ;O*0l t i/C'r-C (>iCC0P;
C.i'iV - .


26
the r e due t i on in he n t ing f i m e It g h oul d he p o in bed ; t
t ha u in o S'i* o I the s an elen to s b e < i I d not e xo e e d 20 gr; i; o *
Had t he y b e on largert 1 on g e r vw a t in g peri c 0 j right have b e en
necessary, One sample i however* weighed. 9 b grans and the
per c en tag e we ighf 1 o so fe r \: h i a go rap A e v'< *. s c o* vp: ib j o t o
that of smaller oamplea of the Siine material, tee Tulle 2
v.i.cl 371 gw re 2 for tre res u 1t s o f t h i s e r e j . j nt=. i; ;u r o 3
graphically illustrates typical weight 1 e; ::: patterne for
J?:l crida che r t s *
A number of satirios which hod coon used far the
experiment described abo*re together with the lx* uaheated Con
trols were placed, in moist pure quarts said loft for
one month. Water was ad do d to the s an a r- e rice 5 e11 y t o
maintain dan ness Heated and undented carpies of the same
:i at e r i al wr r e kep t as o on t r o 1 s at r o c:. L- o r a 11 .re, i h
purpose of this experiment was to determino how much moxsiwr:'
the a 1 x ft ad,y he atea mater!mls \rou 1 i ab s orb as c orr j; arc a t e
ur h n at e b s amp ies subjected to the s a me c on d i t i or s Whs
a me lio. t o :f ; r d a t r re t nh oj up b y the heated s amp A o s vs. s g r e a t:
than that of the animo. U:b., The henten and unbelted controls
1 c i'u : t mi: tonet.:: aturc- drr.in; the :-ou i¡ yi:0.-1.-J. nore in-
I:ure 5 oin g in form;; ¡;icri, Tho controin f th-it hof. nrdp beo,
si;b .1 c: c d i;o hf;ad 1 os t 1 e s s we ir;h u t; .n.; i t h o s o v-: ¡ .o h h id
n o t f e a n h c if a d .6e iabl e 3 j'r t h o re ; s.il r r o f t hi s e xp er i.-
rent. I he ron hod samples won:- then cub noted to heat to
v o 11 t 1 m? ij e i f tnervo 1 ji- s an v s igr i f A c & r o':. o a \ ;.v :< :_;h t j o u b < , r in f' c* i:; a- .; r-; i re t 1 eh t c v'ft : p ht ) r i n o c c urrrt d :f:*


Figure 7*Example of a Potlid Fracture
which Often Occurred when Florida Cherts V/ere
Subjected too Rapidly to 400C Temperatures.


in
VontQor.ery County, Jcv: York: a coche o' .¡.17
airovrocinto on the farm of re-nr a sprins*
They l&y about 6 inches below the yuria^e, on. a bed
of ashes y inch*- s thick, which r-.:3'Jod on v he o x chi or
fireplace*, about 10 feet square of cobble otoos iva:,
the drift. The srrowpointr. evernye about 5 inches jr.
1 en r-;k h and a re o f d nrk-b 1 n e and ?; r av ^ l i r t, i o e .f ah nr c d
(Vilscn 1897 s 971).
Old fort and vi liarle site in 8n3.kn Oounty, lienouri:
Three feet farther fren, the- c.c.nl: .-va if e eire of a
pit f feet in dear' lvj 1 C fe:t in X i a ;.c te?n At one
po:lnt on the hotter. 1 v-.s a -i: c of s..i**u.-o flint chips
scaled off in 'in;; imylws/rtn c sari .1 site or
dedicate f in 1 sh; IK ra *: ~ ve on or.y;- o f th.:i ae to fi.11 a
pirvh cup A i. 3 inhtiy aX 1 c__ ao?. n; y oi* a 1: .¡Isx chip*
lay hiaber up (Powkr 19-1-0 'A;) t
l)y tc he s o Corn 1;y, :i e v 1 c.-:-.v;; T .'hi 1 a ojr .> 1 oy c X. m d 3.ay i j r .j
his spade brov.rni up a ourbar of erro -.-oes uto ho
described them t o b c n i col y p i 1 o X : i o hy s id e-, edpo-
V;is$* in two or- three -vov fle;:o none perhaps tv a cr
three hundred in all. Cn each tide ,*,: on top ve;.r
some charred lops arl stj rf , that termed to le the
.remaina of an old xi vc. They w.* I-', or 19 inches bed ov,
the surface of the porn. They are of a blue t1aspnr/
flint, and seo:.: X a on in u u^fX nir.hr d corn; it ion, I
thou;;ho 'chat rrebffiy the laXian;- h -X broa, ' ihe;:-
from a distance v' s X nave never frv.tX a\:y of the* sute
rock anywhere in this :cr;ir;hbarh-.j:: ) and i.:ade this
pocho t ana covex so. t ie tX'oc.:.j of vhe v by buix e:lr.?
fir a, .intending; to retuve and finish them at their
leisure; or, portaos, t'-v-;, lie' the*, there to prevenc
their capture by the5 v on-..mi2s (hp; -vd 1877. y07-?)*
In loth, 'Ti Oh F. dnyder oir^uvited ios"-.-.: lo, i of t?:-:
Baehr* C roup, o ¡, h a vo s t a 5 ,le o X X i a X 7.i n (' i s h ivc r
fi-ijte-" riles b^ior XharistO.n. and a;rta tiie :;:outh
o f inC. :l ar. Ox1 a o:: X1 i 1 noio J : At i;; i -.; h n f t h e no ur;d
V,7as a.i'i c'ruj of e;;.;/ on. vf '.Lch 8a -' ' of '''lack hoar-
s t or¡ o ir.r 1 e; ;e. n x, s v a t appnr r-. :. 11... k a h c aid ? o > ra :. o -n1
in loto o" C- to 20; i itii so-id ovo-: 1 b.rtv.wen ^ach lev,
a -j thou -;h to i'-oXatc thor. from k.uc"\ o .he;. 'ft. is deposit
o f 8,19 X f.l j r;. t..- v/s c o ve i -e d v < ih : X;. -*. via. o 3' o 7. a j
jG inches in vhic/.wss; and o:\ v-h.: v a fbed been
n.Girtainod for sow tine * f Jin vs. for-.dr.;:
the nuc-ano s orne c. rc a u 1 ; >: n e a 1.1 y i in:- s> ho > b r tvs : -,r sate r y a r t
of thfii1* aro cr \y chirr- wl and ^113- rawrvX the;/
d c e o is t o b ur ulg e d b 1 a -r; '1 : f; ( A1.1. J s 1 !-0: .11A ; ,
It is interno t i' i to noto f.-;> X- real o the to nocoorve
lOvi.ot o V-v w. oal on 7 Cac- nnf1 ni vh: J : 1; / of the .fir-tv.


MATERIALS
The terms chert and flint have been used inter
changeably and it is difficult to determine from the litera
ture if any actual structural differences exist between them.
glint is a term widely used both as a synonym for chert
and for a subvariety of that material. Tarr says that
flint is identical with chert in texture and composi
tion and the term, therefore, should be dropped or re
served for artifacts (Pettijohn 1949: 320).
Thus, in describing chipped stone tools, one might say, for
example, that flint artifacts were manufactured of Arkansas
novaculite, Pennsylvania jasper, etc. This is, of course,
already being done to a certain extent and to those inter
ested in lithic technology information of this nature is
important since it contributes greatly to an understanding
of the kind of workmanship that might be expected or whether
trade relationships existed if the material is not local.
Most archaeologists would define flint as a rock com
posed of microcrystalline quartz that breaks with a conehoidal
fracture. This is an adequate general description, but does
not suffice when specific materials from diverse geographic
areas are being considered. From the standpoint of this in
vestigation, knowledge of the formation and composition of
siliceous materials native to the state of Florida is neces
sary since alteration by heat might not take place at the same
temperature in materials whose structure is slightly different.
18


3
that the "observed behavior" would have been "relevant" to
the problem being investigated if the observers had paid
more attention to detail and had provided a more thorough
description.
In addition, in the section on Methodology, com
parisons are made between materials that have been inten
tionally subjected to heat under controlled conditions and
subsequently flaked with samples exhibiting potlid fractures
where heat has been applied suddenly, e.g., through forest
fires. Other types of fracture resulting from expansion and
contraction are noted. This analysis served as a reminder
that flint materials may break with a conchoidal fracture
but that no bulb of percussion will be present unless impact
has taken place. The archaeological debitage suspected of
being intentionally heated does possess bulbs of percussion.
"Solutions to any problem are at best approximations arrived
at by the elimination of those least likely" (Ascher 1961:
323). In this case, archaeological remains have provided
clues to prehistoric practices through systematic elimina
tion of alternative solutions.
The hypothesis that heat was used by aboriginal
peoples to alter lithic raw materials prior to final manu
facture of chipped stone tools is strengthened by (1) historic
accounts, (2) experimentation with and study of intentional
vs unintentional fractured surfaces, (3) comparisons between
outcrop and site materials, (4) heating experiments with out
crop materials resulting in specimens whose appearance


44
Figure 6.Vitreousness Occurring when
Florida Cherts Are Heated and Subsequently Flaked.
Top: Specimens were Heated Slowly to 550C, left
for 24 Hours, and Cooled in the Oven. Bottom:
Specimen was Heated Slowly to 500C, Left for 5 Hours
and Removed Immediately from the Hot Oven (note relict
dull area that has not been flaked after heating).


1
37
No spalling occurred (except on rare occasions)
when the temperatures were raised very slowly.
2. No explosion occurred even when the temperature
was raised rapidly to 350C, allowed to remain
at 350C for 24 hours, and then moved to 400C.
3. Explosion occurred on all occasions at 400C when
the material was taken to 400C without allowing
the temperature to he raised slowly or at least
leaving it at 350C for an extended period. Smaller
specimens did not explode as readily.
4. If the temperature was raised rapidly, explosion,
or at least some spalling, occurred whenever the
material was removed from the oven at 400C without
allowing it to cool first.
5. If the temperature was raised rapidly, explosion,
or at least some spalling, occurred occasionally
but not often when the material was removed from
the oven at 350C without allowing it to cool first.
6. Explosion did not occur at 300C even when the
material was removed from the 300C oven immediately.
7. Interestingly, explosion rarely occurred at any
temperature when the material was removed immedi
ately from the oven if the temperature had been
raised slowly and maintained at the testing tempera
ture for a sustained period.
8. Explosion never occurred when the material was
tested a second time at the same temperature.
9. When the temperature was raised rapidly a crackling
noise (decrepitation) was often heard at 350C and
always heard at 400C when the material was removed
from the oven without allowing it to first cool.
It was not heard at 300C nor was it heard when
materials were heated for a second time.
10. When samples were placed directly into a preheated
oven at 350C no reaction occurred after 1/2 hour
but all except a sample of Ocala chert snapped In
half when removed from the hot oven and exposed to
air temperature.
11. When samples were placed directly into a preheated
oven at 400C, explosion commenced after approxi
mately 20 minutes. The oven was turned off immedi*
ately; explosion continued intermittently until
the oven cooled to about 375C. All samples had
exploded, including Ocala chert, with the exception
of a sample of High Springs chert which did riot snap
even after removal from the hot oven.


91
a rev? i. of a v a i lrb'1 2 literature has uucvi 1
n* w . o counts o' the r of An re a *3 an cid in io chi. -
v:¡' rH.uss*at least cnorph to warrant the conclusion that
p-i r cof3.es knew that fire was c"coble of producing a
o c-i'':;b 1 c c hoice in f X int materials.
5v -lie problem of racen .crclir;; v: easy test to detc
: i n o 5 i v.c 11 r i a 1 s from archeoj. opic a 1 s i to v ec\ e b a yn in ten -
t' rue 1.1 y altered has not been very re card in;;. Test after
te,. t has not subjected any really re liable criteria. From
cr e: :a mi nation of a represent:-/'iva sc:,e of flaking debris ..
horover, an investigator she;: if find a number of specimens
exhibtine v relict dull area surrounded by ai-spo of entrevi
vitreousness This situation stror:pl;> su^osta that the
dull urea has not been flaked subsequent to he at in r; vheiecc
fhe vit ceous areas have been*
The evidence presented in this report leods to the
conclusion that the manufacture of chipped stone ir.u,lemonee
is easier to exec uto if lit h ic materials a re first c an 15 c u : j
subjected to critical terrier atures (?c;GoC-';00oC for Florida
c he :. t) f o i* s us tailed periods (1 21 honre b u t v a ry i r g v; j t h
s1 o ; izc) c Aiter nearjy tv;o n il 1 ic& years cf e>: "c.ri:-:t...
tv' 'i1 if" ' re and stone, it should ee as nr- su cp rico to
f i r :! t > ia1: p r '..:.!. t iv e p c o \ 3. f: s we re v el 3 are c f t r e a c.v. r tp e
o f t her ral al i. c rati on ,
An t i r a els h a v all. w :-;p. b a n t' a re h i o o 1 op i :j t s > > e s t
f rion-.1. A reco _;r: itif. a of tcx tura 1 ch- i" ,*s ocru.rr.i v ; .;hr-;i
si 3 V cecu-- i: l; t l : *; 1 s ? re t h c r: j a J .1 y a 1t e r >. d j. r ov i d c- 1 r o .:d r;
to j.ishic f ..ch...o*i o ,y :nd ^r?. i tivc i Vih b. vavlvvJ
vs i.o ;V tv. :n tub.¡if.t a )j:.'. vi.oil sc cr"Ch cclo- "i c, 3
ic oerp.-.t'i .


35
(saltss -line ral t <}.) until c-. ckj. hoy ;ou:id is cr.u
or until tr>is sound stops; to crackle when ex otad to ir. ..
.Cxpl o s ion occurs when the s i re os t h o ¡j is c n u o 5 n..; dec .re;:: i t..
tio:i e:-:o :edo the lastre limito of t] : va teriol
\ hen this a t u c 7 was initiated, o e v o re. 1 3 o. 1*3 a c h : a t
fishes were nrepeir 0 in o re or- to tes o t'.c.x- rene-ion rier
heated, The author had 5 ut en o o te raise ths torverct-cc
c-lowly accord:.!' to Crabtree o (personal coj Jun? v i: on
i n 31 r uc t lora b u t the o v en vmg pi* orre s y i r r in d o : r a e s
centigrade chile the author, unfortunately, was thin kins
in decrees fahrerhoit. Too oven conooquoj-tly heatrd :::rr
rap idly t h an b i c i p ; 12 d; At 40C 0 G the racks e xj 1 oc e 0.,
7h0 re1; 11a arc sron .in figure r-<. £ubseonent expsri;:.er*:.
c or* due i e d to d e t e rn ire the reasons for 1; b 0 r o ok fu i 1 ure,
re k-.iI t od i r o.v a o f the m a;j or o o a V rib u t i on 0 of t hi z s b udy.
I if:u.vo 4 Dili s cr:.tes cuite o3 f arly sevc*ic 1 i < o t -;
t b a t re f> < : e o: e c to i._ s ub i c h r .j y o e r a i c: o I v- i t i re pr the itanMoer", t :*r t.irp o:a! subsequent Or-king o;-? ?.;ltbio
:V c r3 :. *:: e r le ture o 1 o;: a o 11: 11 ac 11- r in y an d b Icol y,
ce; vi .r f! a :; th no bull-3 oj oro'1 sico¡ P T1'is kir.a c
hjtrV -i:*':- : ': '.-oc;;-' by :ir l*-. h' >-:,0 r;% It differs
;. : t r i ? y . 'a ti a t' 1 j p v in ; f c vr* j * n n r : f. o c 1 e pic n 1
a i t.tv. h" t -,.'j su 'v o af '*.* c f o i n r z ¡a j *: al J;; lv\ *-e d It
re: le c ' c ; 1 v:i.!: r-'\: or 1 c e.:: r. r. : t o ;' r¡: a j ¡; f ;¡ a i: 1 t o o
rsvi-'i x_ r."- i :;- vid ce:.tracah, occur jw o oras;t
s oc i.l a rech !' ; :.' r ;h;-.:r¡ 01 a'*.re -\ liartl,
: : -BOOMC::: i; 1 o.hk f M '.h a>: : > h : -V ;.lv.! th dv


33
TABLE 5
HEATING EXPERIMENT CONDUCTED TO DETERMINE WEIGHT LOSS OP
ARCHAEOLOGICAL SPECIMENS SUSPECTED OF HAVING BEEN
THERMALLY ALTERED
Sample
Weight Loss
After 24 hr
at 100aC
(#)
After 24 hr
at 400C
(%)
Total
(%)
M
.19
.68
.87
N
.28
.76
1.05
0
.27
.78
1.05
P
.39
.41
.81
R
.56
1.01
S
.35
.85
1.20
T
.4?
.52
.99
U
.36
.55
.91
V
.44
.69
1.13
W
.22
.38
.60
X
.35
.52
.87
Y
.27
.40
.67
Z
.25
.48
.73
35
.42
.59
1.01


90
closer tc ..other when co.-tsin -aterialc cut. tiio.it i:0o k- a.
8J fluxes, '.vhen the flaw is introduced which is preliminary
to find necessary for fracture to occur, the heated reel:
responds more lilts "less than a rock ee-i;,.to. In other
vcrijc, crystal boundarist are re I caps a- irte.vf'niing with
tbs remove.;! of fishes. Those stats.fonts have tec' sub
stantiated throughout tills dissertation by reel rocharles
tests, : i; .a electron cicroscope al1 ustretionr, .analyse/;
deroietj'atir.;/; a reduction in surface urea of heated mate
rials, S3 well as intuitive observations' and experiments.
k. I'xehictcric peoples were aware of the arl von tapes
conferred by thermally altering their litiiic /.ate: iaj a be
cause the chipping debris recovered iron archaeological
sites has been intentionally fished following subjection to
heAt. This is apparent because the fishes have bulbs cf
percussion which demonstrate that there hat boon a point
of ii/ioact. Bulbs of percussion are not exhibit.:: if rod's
explode when too rapid heating or cooling occurs. Instead,
there are "potlid" fractures or conchoids! fractures which
do rot show a point of impact. The fished surface cf the
altered >/ ocinens aro ext.rsvoiy vityc',., varying erg rood --
n'oly fro:; outcrop sampler of the same Materials. Very often
duo, due to ths pr: ranee cf ri.'ut: amounts cf iron, tr ore
is I color cruaye irwi i,rey-bcl.r:o-bro.nj to oink-red. l/wila
color change occurs at. a lower to/vser .vttre than the sir;' i.f i-
cf.nt cUango- re suit ing in easier 11 .i!;;i r / amd wij.3 net ceauu
at. all u oar; iron is present. it moy be considered a reli
able factor if U3... in cor unction with ri pc, tu .


TABLE 1
HEATING EXPERIMENT TO DETERMINE WEIGHT LOSS OF 1-INCH CUBES
Sample
Percentage Weight
Loss
96 hra
144 hra
48 hr
48 hr
48 hr
24 hr
24 hr
24 hr
24 hr
Total
Obsidian
0
0
0
0
0
0
0
0
0
0
Obsidian
0
0
0
0
0
0
0
0
0
0
Silicified
coral
.36
.33
.04
.05
.11
.06
.15
.23
.07
1.40
Silicified
coral
.49
.33
.04
.06
.06
.14
.19
.19
.08
1.58
Ocala
chert
.32
.06
.01
.03
.04
.06
.17
.13
.07
.88
Ocala
chert
.52
*05
.01
.02
.07
.09
.07
.15
.09
.87
ro
aThe total hours of heating for the 100C and the 150C increments actually
were split (that is, 48 and 48, 72 and 72) to determine if additional weight loss
occurred when reheated at the same temperature. When it was determined that no
additional weight loss occurred these two times were combined and the procedure
was discontinued.


TABLE 7
:uwu.vr;; o? atclic abscaptioi spbctagkio ooiibtea Aiumis
PorcoBv'JBe
OC. j .L tf
Kg
Ac
da
i-
On
2
Jor.c son Lt ke
(Tine £ r a Inocl)
.010
.230
.033
. 005
.Cl?
.010
Oornsor. Lake
(coa r r o c; a a in c d)
moo
,0.00
.013
.016
.010
.020
Lie'- S>>rin3fc
.011
.1113
. 095
.033
.010
. 012
Oc a 1 a
.010
.230
6.600
. ('^-0
025
.050


26
the reduction in heating time. It should be pointed out
that most of the samples tested did not exceed 20 grams.
Had they been larger, longer heating periods might have been
necessary. One sample, however, weighed 95 grams and the
percentage weight loss for this sample was comparable to
that of smaller samples of the same material. See Table 2
and Figure 2 for the results of this experiment. Figure 3
graphically illustrates typical weight loss patterns for
Florida cherts.
A number of samples which had been used for the
experiment described above together with their unheated con-
trols were placed in moist pure quartz sand and left for
one month. Water was added to the sand periodically to
maintain dampness. Heated and unheated samples of the same
material were kept as controls at room temperature. The
purpose of this experiment was to determine how much moisture
the already heated materials would absorb as compared to
unheated samples subjected to the same conditions. The
amount of moisture taken up by the heated samples was greater
than that of the unheated. The heated and unheated controls
left at room temperature during the month yielded some in
teresting information. The controls, that had already been
subjected to heat, lost less weight than those which had
not been heated. See Table 3 for the results of this experi
ment. The soaked samples were then subjected to heat to
determine if there was any significant difference in the
amount of weight loss between the heated and unheated samples
or in the temperature at which the weight loss occurred. See


75
Ocala cnsrt) 2n.:3 :¡ ah fl: at, bc.idi.en, 'uto
nade with t. ;> So i Is Lhr rfcL.< nt at bir Univox sily
Florida to use the differential thornal c':\jysis equipo en ,
The results of this e**; -or ir out v:crs ercou.iv. :,in;_ since they
sub cl an tinten data obtained iron the weight loro expori-
iiioni, .is the surpje tnkea on energy (neat), mor is
driven off* This was apparent by the endothermic peaks at
112 0 as she wn in Fi£ure 15 Tor opc.1. tVohn.sou 3-oka cbort
net previously heated, Ocala che.it) and jins lis!; film,.
This was due to the removal of the adsorbed water hold on
the surfaces of the micrccrystals. In the pure quarts scur.-
p3 r t h e aires d y ho tod che r t sample t he hip h Sp r in a o c .'a r i
e&q.'h, and obsidian there is no peak at 112C, Those nato-
rich c have already been devolatilized or there is no noinrm
to ri ve o if.. Tile only unor.a,! y i b c seers to e xit is lha I;
the chert from Hi ah Springs which is CXipoceoe in ape did
l\ o t s ho w c no a k at 1 j X 0. Th i -s m at erial is :: o r o c c r: s 3- y
c ry31:- i X ine 111an rx>oh of o thor I'l orida mater i 3 Thi a i aa t
is borne our by the quartz peak at 5753 occurring v/ith this
s e '!i__ X v end the pure- qu ..i r t z c s jupio. Thi a ;: e ok re p re s on to the
i ..ha--hoc o o v a-qp in tie crystal lattice, and it ic ir.rediat
as the sharp peel indicates. This inversion reaction is
reveroik!e in boating end coolies.
he check 'V- vrliiity of to-; dob hemic trend u>
fjinniny aba at 550C~tOOc C (,.ee Figuro 3 0) additional or;pie
V; e re p ro p a re d an d t e n b e d a = oof oro f h c- so T.atorial f > ; ;o re
rorun to dc torame i i' 11 e end.ut .cnj c hro,d ;;-c.i.c : 11 np ¡n


I certify thi I r:¡ve rc. .. th... xtu', t\ in ny
opinion it comorrj to acco table stanu .-.tls or scholarly
pr-e sen tat ion -?: 1 is ful ly ade qua t e in s c oye and. qual i ty,
a 0 a d x. 0 c / t ^ 1; x o 1 10.0 xhe do y reo of Joe t o r o £ 1 h i 1 o s ophy.
Profesaor of Anthroyc1ogy
1 certify that 1 have read this study and that in ry
opinion it conforms to acco .table standards 01 scholarly
pro sent at 1 on a1 id in ful 1 y rd q u at e, :! r v c o y 0 and quality,
as a d ia acrt e t ion for t ho 6.egre e o 1 Joo t.0 j/ o:C Phi 1 o0 0phy,
1 certify that 1 hc.ve read chis study and that :o ...y
opinion 2 u ecu horns to acce; tub] 0 standards of ac'ol only
p re s e n c at 1n ;j:q 2 s f u 11 y a d e y.: 1 b e i r. e a o p o a : q u . J ity,
at a dissertation for the deyroe of hector of 1 hi iosophy.
I certify that 1 have read this study at?, that in iyy
Oji'iim' i !: c.:nfori is to acceptat- 10 >tand. --is of echo 1 ar 1 y
v o s on i ? L i en m l i:: fully ad o y uax o 5 in sc oy 0 a:: d qua 1 i t y,
as a dissertation for the decree cf Tactor cl Philosophy,
Ass ocite fro f e s s or of Go o* o; y


observance ox the phenonenon of thorns 1 alteration stinulated
the undertaking of this study. During the summer of 1969
I attended a four-week Flintworking Session conducted by
Ir, Grabtree at Shoshone Falls, Idaho. This session was
sponsored by Idaho State University with funds rrantod by
the Kational Science Foundation. ir. Crabtree's encourage-
ment and suggestions through personal conversat i on s at that
time as well as subsequent written communications nave been
inva 1 u ao 1 e, Dr. F. V. Settler of t he FI an t r a thole L;y
Department at the University of Florida,who gave so generously
of his tine in helping me with the photographs, but whose
real contribution vas his enthusiasm which is more infectious
than he realises. Dr. H. Y.. Brocks of the Geology Department
without whose help this project could not have proceeded
beyond sr idea. No phase of this study was undertaken or
completed without hi.? physica 1 and menta.1 particxation.
Lastly, I would like to thank the members of ry
famj1y for their patienen since 1964.



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81,9(56,7< 2) )/25,'$


INTRO UCTJ. . k<
A rvocmt tiu'.. 1 ic"ition (Or btre o : Ni-; 1* Vi;
suOe-:: tec. tnot pro-. :i fcoric ir.fin i: ce/ ha^a it ntaae-
our to theme.IIy alter hie 1.1th io rev iaj_ial3 evio:- to
nanU-fae ture or fin al oo;ra¡loti">n o i chi nj>. b t on o .. iera-., t a .
otj.o s e n c r t e a -tin a t 1 on c _f f' i;;.- ye c¡ at on e t o o j e a s : -'a .1 "L i: o I
tffstr II3''gr recovered Iron £robrealorjicnl titeo lot to aha
s o o c- \ i''.1 i r- r. t he. t i r i r t n ?.} :n i :i;c 2i a d b :* ; en o 1 o ?/e d at c : i. i o -
any in t. e a fcetc ai Florida, Florid3 materials citen
ox;i b 11 uhf.'. :; i a.hi3h 3 j o t a/*.d v i tre ona '} r r. t er ?a i t v c fc-:
no. :1 c i :l v : oa he re 1 al t era tier- ojt cl d: .i .7c r rlc e 1.1' .iV e
tho a j. I i c c oy: ' a t. o r : a i r Ioun-i in c.it:c oj: a.
c .a '.c r- v.r i :: 17!?-: t; o fc r r h e udie "
L he c o 11o i o f a i o.*e t o e 1 e i n t; Pi::? id a 31 t 2. un - \o ,
ir a i:* o > ¡. a Rr- ¡ va:: y ?! o ri 7 a o ov l r i'o r : a. s c n i c d bi: t
-\r :car--aa \v-.-:. ecu-: t5 .:? rh-re baar' era v-c> n- L'.-r-1
aun - ; c.. r1. : r ifc** '.oria.o., ; n ve. f* -da:
act ,.v:,U jir. rr i'-.; be -n r- a-i-jed, ..or ; r.
;o-r a r;-l on t o i .nr Vhroyoi ov y at ha
o.V lo.-i i -. :V.t i. : n ':?.J et't a "aterialt
roe ov .i 1 v ae i o :or ; o r-,. deb 3 t : ': r;
'i an +b.'J *: 'nv... .-a, i, -;rv '.i'
'lC: caia


29
} .00
P
,85l
4
4\
'i \
5i< i
*t,!
f 11
. 50!.
u
;T
-i
, 1C..
X
\
o- Short,
Chert fro:.i torte'o property,
A5 Oicb.ro* County, Jloriir
!-
'VXs
/ XV.
/ IC'
X
7
100 lyO 200 X>0 500 550 400 4.50 5u0 550 600
T-^ifipeu l v.i*e ( C )
XVoipht Lo-.s ci -S. o ylor:Ciisri*
tie lij yicrl X aO'C-ivi Cbse ::. e * for* All ilLoricLa
Oreov/.x.r1io.olod /^ro '. IVo-Yg. ) I-c^lod (Cbf.idi an,
A.-:k'15.:i1 d)d ru.t follow this
raster1;: 'i.


*¡5
the ohimse v; . r* re ac H o d ai; d a.in .:b 7 r d 1 111 b Y o e V. 1; 30
o e ci rr e d Oh air:, an ( ? 01 e 1 ; i o c t n c 1: e 3a ;¡t a t a i 1 a _ u
oti'ie r t r p u :3 an 3^ 0 at t r it a c h 0 y. 2 1-.h t c * 0u f s ; c ft e con
on bt ro r y t h Te ts) .1 onuria c 17a to?. :,-1 y-n 1 >; a:. 0. y 20rl
1 a\ vry livcle v/aiybt (otter L onro at they a a
2 i -r t 01?.' and O'1/, re r pc;013 vo . la; t :i mo r. on et... -:0 j
that ev. .-t: taco.'.53 rosier to .Cr-Ho (C:?Mr:0: cora.rx. 1
about to 25b ana, bee :t io X:i nr. :-;x:.J* cad s re
bcapeo to bV.at 1_->e yre: nad .FIocl0a cb&v \:o til a loa0 i
v.v i a ri t c : r' c o an3 e r,:o a3 no d F j r r J 1 a e be : i;: oxu j. .r j_c 3 e.r re :
Ho; -e -'e r t Ho:?c doa r n c t sec.; t c t. c; y?:.'. S ;¡ c : t. y re -
d i a tab ?. e C ixi'c ne nee b e t v: 0 e n t r 1 ar: 01 cr> e. c t v.*s i ¡: h b l o a t . a d
crystal arse in Florida chortr, Fhis cc-v.id be -., tv
he t . r o y re .i t i c a si a c e e ven £ in a -;ra :1 r > e d .:;=r 0 ri -. 1 a . ? y ¡ e 0
1 a :ra;e vo id. a;. - e e s t hat e am\ a ; c na i 1 y hd a t e c t ad, i i3
lOJ-e liholy r;:caisc, even though ti a;.; la lo:;.- wetev in
?T* y g.L v ox: i r¡ t e rs t :1 > a 1 s p 0 e e 1; .;a: . t in c _ y:-121 :0 a a ' .
i- e, ?>ro sli?;! '..rd. a? en?, end yrobeb.ly ore r.ot aacavd any
belter t; m. j.::-.- ...' va a ; L bane poo, : :.e . ai.aj a <>\r-. w of
v earn; a 07 r Fa? c ey b"': a tie a : t f-u*:. o..u r..
...; (* e in r. 1 'i c f. 2* ¡ ... 'a m -y; t j : m; I;. ,v n j -y <
f lXt eo'; '. ; cu tc VJ o?aid; cmet iy ,t ';: o th; ecppCl -
t x arts .r; dr \c a 1..,;; v 2 re ?'..: ; i K; ; j ? 1 0!:c vi r -o'-
e >.1' c a 1; . : c re v.b0.;: vs cu a?, a r XH c ;toc; a t- c X
F-;va ie 1 £"l v e r.- . voa;b 1 y .o 1 e a...c c1..a:? i:Lo ar ni
the vise cr the- cri>T.t,,,:;5 H .*l rv.¡rf:


58
Figure 10.Heated Specimens and Unheated
Controls Illustrating Degree of Color Change
Depending upon the Amount of Iron Present in the
Chert.


caire t';o
A ))1L : . 'i:;.
foi" cf
' x
'.AO.:'
' u c
. l'.
-t. o:


:i-i.c -'Ti e:
a:?c.'i .Vvi
If an arc a e elopie t in opectr that iha ch? :psd .-1 o
r oTiain ho roo ovei'S r o:: si t o h a vs toon 1b e i y a 11 e re d,
it would bo cos.iraolo to subject these **::tori.als to a
> t and arc ia t o 31 in o ri or to 21 i_:i r: a t s i h 0 1 g a 0 '" 1 ao b 0 r.
I'll i c :< a :* :rc or tan t a i a c 0 3 hern al a} terati on a re pen is in f c ru <
tion concernin'.; not only stone technology, bub contributes
ultimtcly tc a praetor valorsfundinn of prehistoric sa;i'::
bohav ior-j.1 patterns. 1>\ i s bco^ioos evon r.-ore val''.able if an
investir tor is working on tire levels vine re only store
arti 13ot hav0 been proserv0c .
The fcl].ov;indisc.ur 3ion ir. vciv'.'; a revi ov; of the
:,: ;ny o:u e"Irenes cr ...duc10cL thrcupbcut the c0ursc of this
study to d:-tten. 5ns i-' one or :/.re o these uioUt feasibly be
replied to site unte rials, .'tor a fuller account of these
ovi'orirn r.-ts, the roedor is advised tc refer to the scot cr
on he Li'O 7 oleyy,
Voirbt loss car riot h- rood an a criterion to
determine if t_.ee im^ns had been th email;/ altered because
eve,-orino rio acre:; at re led th: 1 he a tea spec irons tended to
bnhe. on .ri.anr: a ein. In other words if an arehaeol-
cf ;i- t vc i_ hu- 5 i.c ai0d, or:d revoipho0. outcrop i::atorials nj c p
i i ¡ sit' . n t e r i nl s S:c oheck a i f f or o ices in v:e is;ht 1 oss he
-. r00 ?10 ;/ . .) a 1 d f i !\r p .1 o .1 p i: ic ;.i a t d.i f .1.'er : n c 0 -In d e v o n i 1'


1. , X- Ray !) i i i* : .i . t *>s II1ve t i t' A o
Ch-./v. .o Oo',." r 1 -.Lo or : 7/ x 'lori
Cae :ci r- Are oj o ,i e 1; a i t o Ci1 :> ; c a1 j. r : a r a g . ?A
15. Resulto of Differ; r.lial ;A varal Analysis . . 7'1
16. l'etx'otj-vophio octions 3Lcv;:ui; I. o Cogo tab le Glande
in Rer.G;*a va Ui. acate! Rio i 1A a Clieit , 77
17. Surface Toe\'jr-a.pv.y c.f ULheaaoe r.r.'i la ted 1 o! 1 en
La ke Che r err J.* s a o V xa -c !y i: c Le a: -..u : j _;
Ele o tren i .loros cae o 00
13. Sur fe o o Topo;; r v. hy o.f Unh.o at: J ar d J le ata d o i 1 i o i:? i e d
C o rai f r o;. l-l o r!.. a a e. V x -- . 1 o d > y t:: e Lev y .i n ;
Electron VSeroacope B1
19. Specimens ir ex. tac University cf Herida Gol A ce i en 3
Ehot-i.;.! Lull Arcan ]Rit rivera Su o so .*i:vu V H e 7 a a 1
A.11evav5 o. \ 3urroundcd "by Eat ro: r 7 itreoup _. In
Arc o s that. Have Been leReu efter Al te:, -j ti yo Of.


t lift fc tbs n ob s e rve d b e h av i or v;o'*.\ 1 d n b ; n : 1 j : c , t!i .o
the problem be inf; invectiva ted if the obre rv.vvz had rs'd
more attention to detail and bad provided a more thorough
description ,
In additiont in the section, or Let ho do I a ".7, ocu
par i s on a re iiad e be t :e en mat e r i e 1 s 11 t he v c b 3 cr : n ton-
11 cu a j. 1 v s a b:} e c t e d t o h oat v j ide r c on 11 oj. : c or d i. .1 an a\ id
s ob 3 e c ue n 11 y f 1 a? co c. r i t h s nr p 1 o s e xliib i v in v o 1 1 :<.fr a a v* rrs
v*her e ho o t bao been applled suddonly, e. , t hrouj b f ;>re c t
£i ros. Ctnei* types of fracture resulting fro:.* expone j. on and
coni:action are noted. This analysis served as a r>:iiador
t ha b f 1:; ji t na t c r-i a I 3 uay b re ah w 11 h a c on o h o:. u I f r a 3 t r o
b u fc t h a t no b u lb 0; y ere us s i on \; i 11 b e p x e s 0 r t nr- J a 3 3 u p, c c
has taken place. The archaeological debitega suspected of
being intentionally heated does possess bulbs of poreuroion.
:i bo J u.t i on z t o any pr obi era c. re at best approx i a t on s or rive ^
at by vl.2 elluination of those least likely'1 (Asonar ifbl ;
f -? 5 ) In : h r s o as d 5 v c . .-* o o 1 c 0 ;i e a 1 re: 1: a 1 ns b s vc p re v : d ? '
c .1 ue f c p r o h i -1 o r 5 c practice r-. t trough 3 31 eun t ic o 31 r i n;. -
t i o: : o A a 11 c rv. a i iv e s o 1 u t j o; .13.
Th-- 1: yr. o t h cois i v t h:: at v. s :j un j o V-./ n.b e rig in a 1
pc o pi . x ai j a r 15 t'' i c r aw -f: ' t " r 1 j1 3 r t o: !.; > f ir a 1 j mnu -
f uc t uro o f r. !'i: pp e d t o n o t o o i c i o v ro nt b ;'. s . i by (1) hi 11 or
ac c oun t s v ( 2 ) e x* e 3v i:u a t a 1, i o n v. i \ 1e n 0 n tv:y of i: t (; n t j on al
vs uniat ntArctured sorfac.a, (5) uf/.:.avi-rv.< between
out croc and -j.tc re t.sri-'l.: > (! ) hr c. r r.: r. .'..b out
c4a . i.%ic. 1 r> 3-t;3u 11i\g i sr eciu>¡rs vhc.:'1 j~v


LIST OF FIGURES
1. Areal Distribution of Outcrops Probably Containing
Chert in Peninsular Florida ...... 21
2.Weight Loss upon Heating of Cherts from Various
Locations in Florida ........ 28
3. Weight Loss of Samples of Florida Chert Illustrating
the Typical Pattern Observed for All Florida
Specimens Tested Throughout a Two-Year Period ... 29
4. Explosion Resulting from Too Rapid Exposure to Heat 36
5. Results of Experiment Conducted to Test the Validity
of "Flaking" Hot Stones by Dripping Gold Water
on Them ..... ........ 39
6. Vitreousness Occurring when Florida Cherts Are
Heated and Subsequently Flaked 44
7. Example of a Potlid Fracture which Often Occurred
when Florida Cherts Were Subjected too Rapidly
to 400C Temperatures ....... 54
8. Examples of a "Crenated" Fracture which Often
Occurred when Specimens Were Removed Directly from
a Hot Oven to a Cool Environment ......... 55
9. Specimen Depicting Intentional Fracture with Bulb
of Percussion and Typical Fractured Surface
Emphasizing that Impact Has Occurred ....... 56
10. Heated Specimens and Unheated Controls Illustrating
Degree of Color Change Depending upon the Amount
of Iron Present in the Chert 58
11. Composite Illustration of: (a) Drill Press,
(b) Corematic Diamond Core Bit, and (c) a Chert
Nodule with Cores Removed to Be Used for
Strength Tests 61
12. Decrease or Increase in Compressive Strength over
Unheated Controls of Heated Specimens 64
13. Composite Illustration of: (a) Compressive Strength
Testing Machine, (b) Close Up of Jig with Core in
Position, and (c) Core Split by Application of
Point Tensile Load. 67
vi


nu.iii
:i: ii.v:
J-.. ji.be o.oror; -1or y c o: r on. t e ; rr s h o
ho .i*ov -a -1' T-h o t svb ec t inf 1; nt to f ?<: on ?. y o e f ¡!; r i
t:.ve effects (o*G*, fond I9;>0; dUIdl) v crcvyl firs burr
a o c o un l a exist ( e , Sc h xzel ao he r 1 8'/ ?; r *>!. o r .1 87 7: 1 n
18c-3) to vc:.-ran 1 invest!Ration o.F the techrtore.
¡yion s Iv s oxeo rimen t s c c ncluc l c d * ro o, h out a too -
;yo ar * ori cd, in whic i iiint materials i; rc ;cc to ho a t
wider mrorous diverse conditions, h \v j cl..on.-¡.rated tort
the alvenation of siliceous rocks, vori critic.!; tero '-ro
tures art reached siovjly and maintcinch Coi a su., sained
revi of ro'bab 1 y c onf orre d ai i aovar t :.c o r o ;; i..: , i ' r or :i:-.ar
i Vi V ox n f a c tu r i n ; his chipped s tor o ivc 3 t n t s
vh 0 oi11-'quoted a0 !;hc-d o i drip r: r c c 1 d . r i a v hc t
rec :: c 1 s been 1 rgo 3 re s r or s ib.1 e f or 0. : ; r d 1 t. s f f j re
c. s a e oj j i ;/ :l b u t inesc so r n fi;! at u j r i i ; : c h. v. e 1 o g;,-.
;;11 r:.jtr- hy t 1 is irr'c;t: yc,tar ;;o r,cMl' . th c 11 j vr.I .r
;:>rc v':. mc ed n o S' j c > -r: c b oil and re v iO v .1. 5 . a c r v: ¡ c < t' 1
roer i; .11.". c ru > f i l- ¡ < n L- t he find in a o f r cv (11; C ) s n11 ; .1: *.
(19' / >) ;: o v v e r i i 1 0 *. o r c 1-" r-cr to r h -v ;v, c _ o i 1 c v : c'
Clo77), ; ovrrs (li7v), and I.-.n (.'iSll, 1. ; v;. :cr'v:-v..l
ov rocks fror- a hot f j c after }Jch tr y ; : v: c ir. ir.-
i; olai-er 1::, .he or 1 y cbyjctiov to tlv . c:-;- v : ;J c; r
hr.:v! Lv ^ \ 1 ere :-t:; i 1 ah 8. sod r- ti rv : v ' . ? .
87


76
Three additional slides of Johnson Lake chert were
ground to 3^? which is standard petrographic thickness, to
determine if thermal stresses could be detected which may
have been generated within the grain by the application of
heat. At a magnification of 430X no differences were ob
served for an unheated control, a specimen heated to 400C
and allowed to cool in the oven, and a specimen heated to
400G and removed immediately from the oven to a cool environ
ment (see Figure 16). Thus, despite the fact that strength
tests revealed a significant reduction or increase in
strength between heated and unheated cherts, and that point
tensile tests indicated there is an even greater reduction
if materials are removed immediately from a hot oven, these
changes are not observable petrographically.
Determination of Specific Surface Area
The method involved in determining the surface area
consisted of the gas absorption technique in which helium is
used. The data were analyzed by an Orr Surface-Area Pore-
Volume Analyzer. Four samples were submitted: High Springs
Oligocene chert which is coarse grained and gave a quartz
inversion peak on differential thermal analysis, Johnson
Lake Eocene chert which is fine grained, and Eocene chert
from north of Ocalaboth heated and unheated. The results
of the tests on the unheated cherts were consistent with their
grain size and packing. The least specific surface area was
4.64 M^/g for the High Springs chert; 539 M^/g for the
Johnson Lake chert; and 4.86 M /g for the Eocene chert


24
procedure was followed for 1500, 200*0, and so on through
500G but it was not felt necessary to subject the specimens
to such long periods of heat or to reheat them at each suc
ceeding temperature since no additional significant weight
loss occurred with prolonged heating or subsequent heating
at the same temperature (The validity of this procedure
is established when the next experiment is described.) The
results of this experiment are given in Table 1.
Twenty-six specimens consisting of samples from
14 chert nodules obtained from various areas of Florida
plus one specimen of English flint were weighed, heated,
reweighed, reheated, and reweighed again through successive
temperatures to 500G in the following way. After the
initial weighing, the samples were heated at 100C for hours
after which they were removed from the oven while hot, placed
immediately in a desiccator, and reweighed when thoroughly
cool. They were returned to the oven and again heated to
100C for an additional 4 hours and subjected to the same
procedure as described above. This process was repeated
until 500C was reached. The oven was taken to the testing
temperature at 50C increments, left at each increment for
1 hour, and then moved up. In other words, it took an
additional hour to reach each succeeding temperature. The
only variation which occurred within the experiment was
that it was not considered necessary to subject the material
to a total of 58 hours at each temperature as had been done
at 1000 The fact that no significant additional weight
loss occurred by reheating at the same temperature justifies


8
Holmes (1919: 364-5) quotes accounts of the Digger
Indians on the eastern side of the Sacramento River and of
the Seri Indians of western Sonora, Mexico, who employed
essentially the same technique. It would appear that these
methods were not actually observed by the recorders.
Ellis (1940a: 42) furnishes other accounts pertaining
to the Athabascan use of this method and describes several
experiments where "chipping" in this way was attempted in
order to settle the question as to whether dripping water
to remove flakes is fact or myth.,' He says:
Experimental attempts to duplicate this fracturing
technique have shown it to be very unsatisfactory. In
the first place flint exposed to an open flame for even
a short length of time will heat through and shatter
into angular fragments and tiny flakes. The portions
of the flint which do not shatter may be treated with
cold water dropped from the end of a stick or by other
means with little reaction. The usual result of the
application of cold water to hot flint is the boiling
and rapid evaporation of the drops of water. Occasion
ally small chips may fly off, but their direction and
position cannot be controlled. Dropping thoroughly
heated flint into a pan of cold water will simply re
move tiny fragments which are broken away by the sudden
change in temperature, but often even this treatment
has negative results. Also the flint which has been
subjected to fire is so filled with tiny fire cracks
and the surfaces of the material so roughened due to
the differential expansion of the crystals caused by
the heating, that it is impossible to use it to any
practical advantage in the shaping of stone implements.
An examination of thousands of specimens in the museum
failed to indicate that fire played any part in their
manufacture (Ellis 1940a: 43).
Pond6s (1930: 25) account is in complete agreement
with Ellis.
An experiment was carried out which is described
in the section on Methodology that was conducted prior to
a knowledge of Ellis' work. The results were identical.


?
Exposure of hi fot :'C t;
Aid Tn \Tho~C~j.T^ *_Jj. 11 1
This categ orj do als rimo? i jo- a i tr> ... ;ti : r! ac e o \y;..
or, per1'.-a pa more accurately, fane lfu.ll .Into rare tat leas of
f l:c j t h and o o c o un t s.
11 s a a ins apprc priat c t o r on t ion r -r f 111 o v, o *: 1 *
ksA/wn description. v:ii.:.eh appears to have bee ;; to gewv o ith
)If; r:i';v. Lekmc?:.o :
Vs threw a large flirt clone, from boo to six
feel ir circumference, into the lira. After the
ato;:>e beoamo very hct, smal.1 t hin pie c e 3 v-'on 1 a pop
of f; v;o se ] ec ted rh ose p3 oce s v;hj c h woul d re qu:i re
the least work to put into ohope, and picked these
Piecec up it}? s s cick sp3 it et ze end *( *dJ.i ? t'Vse
piece v wore very hot, ve dropped e o 3 d ¡v. : oa the;::;
places *.:e wished to- thin dov,v<; the or lid .star u'Jwod
the soot torched to chin off, and .in ibis voy we as* cla
some of the keenest pointed and nharper- [ erre.-a th;.t
could be fashioned out of stone (V/'al.-.ac-o w bo?be3
i 9y?: 10.
Ill cup1,! widely see anted by iap-aa, :-? "srpr-inr '?
be or. 1 o rp o 1 y di s era d i to t b y .caos t r-r o f e c s :i o" ;. " s V o to s :i.-
who sro sophist ieatso. in tbo ax-1 of f 13 a\ aw -pp 1 ny, 1 i dces
scorn i i V.:o r v;.; ? t o c f : :<. ;;.o t o u o c t h ia r a t i c , e v c :. : : cn o
e ou 1 t c x>;i t rol t he dr ipping o f v--a t o r n u ff i c ;l.t y o ore t ic t
the type of Hole that would be removed; the work row.-a
v r c-* T: t rc h f p ?; t o * b y v r. in y a. po r c u s- l or or p re o.; i!: t o o 1,
Al o J j y i- h isane 13: k , ; -o J u.o v< (1 v 19 15A ) c :i i ^ a '1A
re r a.vh ? ib 1 e ao c cavo t o f t he u s e c f f J re in c t yp j \._ f .1 vr v :i .>
pi ementa t furnijh'ed. by Tro.vs II* fra'V.vf w'1 o
was infoj-. d by Cnic-f .ion 1, the ed cl r-.r.r.- no
of the I io-s.rc trio?- rcsidsrt o'; lh- ir i hrv coo <
of Iova Hr.ot:i,r- 5 t;ixv in. hi, f;rrn ^ f ; r a rr o \¡ *h :* ed a a c re ma-' i o b y fc h o sy a t s -.. 1 n ;;pi ;i r. s -if
f: re end ..-.tor, raid J sti 11 : \ c jo .; w-e * lo c '
aiTCOv ~*h:.--td :

93
FOLK, ROBERT L. AND CHARLES EDWARD WEAVER
1952 A Study of the Texture and Composition of Chert.
American Journal of Science, Vol. 250, pp. 498-
510. New Haven.
FOWKE, GERARD
1896 Stone Art. Thirteenth Annual Report of the
Bureau of American Ethnology, for the years
15^1^2, pp. 47-178 Washington.
1910 Antiquities of Central and Southeastern Missouri.
Bureau of American Ethnology, Bulletin. No. 37
Washington.
GREEN, H. W.
1%7 Quartz: Extreme Preferred Orientation Produced
by Annealing. Science, Vol. 157 September 22,
pp. 1444-7. Washington.
HAMMATT, HALLETT H.
1970 A Paleo-Indian Butchering Kit. American Antiquity,
Vol. 55, No. 2, pp. 141-4. Salt Lake City.
HOLMES, W. H.
1893 Stone Implements of the Potomac-Chesapeake
Tidewater Province. Fifteenth Annual Report
of the Bureau of American Ethnology, pp. 3-152.
Washington.
1919 Handbook of Aboriginal American Antiquities.
Part I. Introductorythe Lithic Industries.
Bureau of American Ethnology, Bulletin, No. 60.
Washington.
KERKHOF, FRANK AND BANSJURGEN MULLER-BECK
1969 On the Significance of Impact Marks on Stone
Objects Concerning Fracture Mechanism. Glas-
technische Berichte, Vol. 42, No. 10, ppT~439-48.
Frankfurt Am Main. [In German]
KRINSLEY, DAVID AND STANLEY MARGOLIS
1968 A Study of Quartz Sand Grain Surface Textures
with the Scanning Electron Microscope. Trans
actions of the New York Academy of Sciences,
pp. 457-77 New York.
LUTTON, R. J.
1969 Systematic Mapping of Fracture Morphology.
Bulletin of the Geological Society of America,
Vol. 80, No. 10, pp. 2061-5. Boulder.
MAN, E. H.
1883 On the Aboriginal Inhabitants of the Andaman
Islands. The Journal of the Anthropological
Institute of Great Britain and Ireland, Vol. 12,
PP 379-91. Condon.


16
aay bs cono Jaded, ft ..-reforo, that Crt'. Vt -. e
nade a significant and origina' contribution with bis ob
servation, experimentation, and descripcin. of tais phenom
enon .
I first, discovered the then-.si r; ti e i~ . .Vv. I
was about 1?. I would find ivorhed cbori;. i : ¡ iicft-'-riol
of superb quality, but vlien I feuv.; fh. rev ter: ;r
source it was never the se.jj end liad e.n on;irc-l;/ dif
ferent texture 1 iinallj -..'onrter-r.c f.J they Ira in
porno wey treated the stor:a at A. sc ioi'd. fnc "Id seal
range and heated, the roche vhiuh I burted Ar via.
/.ftar Much trial end. errar, 1 was able to du; Areata
the toxtu.ee of the werhad pieces and decided iVa,
was What the? irusi have done. A. could >,oU no one tc
accept the thec-r^, hovevor, until the Les yost
conference in 196-''-. Ti.-d.er eccen-.-od it readily ns
he had encountered the sot-a complex pret.l.eu in .41rp.-/-ia
(Crabtree 1969-, personal eoser-ir ication).
Since 19&4, ony archaeologists throughout the id. -< and Cid
V.orlds are beeAopi.rg to suspect that r-ucb of the £to:.e re
mains recovered from archaeological sites has been eubjenyen
to there,el treatment.
Since the Literatura Review has revealed no accurat--
earl.y deKcripcion relative to this probier, that night bn
applies to o.'\:hn>Ciio5a:0. finir-, at least : pse-ci -n c-f i. e
major cciiti .Ihus.i vi aired at in this J eve. '...'. v. ' to
have failed, A.e., it should be possibly to is... nrtrnt they
prehi -it eric peoples i-cre a ware cf the- ah v anteras conferred
by v hart ally altering their lifthic aterais. However,
enough accounts exist descrih:-v; the use of fire in cono
photo of the Vt.nv fee ture of f 1 j..-: c tools that too evidence
cannot be- cc.fieidevt-d entirely negativa. It is not strprA is
that accurate so counts o r.ot exist when it is tab-.: into
cei.vidarai.i c:: that:


10
Thus, there appears to be even less information
from European sources than from the lew World, However,
the following account concerning the Andaman Islanders
demonstrates that the intentional heating of stone to cause
alteration was not unknown to certain groups in the Old
World. This is even the more interesting since the Andaman
Islanders were reported to have no knowledge of how to
kindle fire.
Chips and flakes are never used more than once;
in fact, several are generally employed in each
operation. . Flaking is regarded as one of the
duties of women, and is usually performed by them.
For making chips two pieces of white quartz are
needed; the stones are not pressed against the thigh,
nor are they bound round tightly so as to increase
the line of least resistance to the blow of the flaker;
but one of the pieces is first heated and afterwards
allowed to cool, it is then held firmly and struck at
right angles with the other stone: by this means is
obtained in a few moments a number of fragments suit
able for the purposes above mentioned . (Han 1883:
380).
A paraphrasing of this quotation is to be found in
Mason (1895: 137)*
Use of Fire in Quarrying Operations
The information contained in this category comes
from archaeological excavations and observations made at
quarry sites no longer in operation.
The most widely quoted use of fire in aboriginal
quarry sites is that of Fowke in his description of Flint
Hidge, Ohio:
. Traces of fire were plainly visible in the
pits, from which the inference is natural that fires
were built upon the rock, and that, while heated,
water was thrown on it. The stone could thus be
broken into pieces (Wil'scn 1897: 870).


ACKNOWLEDGMENTS
This study could not have been undertaken or suc
cessfully completed without the cooperation of many people
with varying scientific backgrounds who contributed their
knowledge, time, and equipment. This type of interdisci
plinary approach is increasingly important as specializa
tion becomes a necessity in an extremely complex world.
The author wishes to express appreciation to the
Department of Metallurgy for making it possible to use the
Scanning Electron Microscope; the Civil Engineering Depart
ment for the use of their equipment and for assisting with
the rock mechanics tests; the Soils Department for the use
of their ovens, for assisting with differential thermal
analysis, and for conducting the atomic spectrophometer
analysis; the Geology Department for assisting with petro
graphic analysis, determination of surface area and porosity
of Florida cherts, and for permitting extended use of their
oven; the members of my Supervisory Committee, especially
Dr. Charles H. Fairbanks, for suggesting and approving of
these investigations and for editorial assistance.
There are always special people without whose sup
port graduate students might find completion of research
projects overwhelming or impossible. This author is very
grateful to: Mr. Don Crabtree of Kimberley, Idaho, whose
ii


54
Figure 7Example of a Potlid Fracture
which Often Occurred when Florida Cherts 'Were
Subjected too Rapidly to 400C Temperatures.


firmly cement the microcrystals of quartz. This fusion led
to approximately a 45% reduction in strength necessary to
fracture Florida cherts -under point tensile load, and approxi
mately a 60% reduction in the intergranular surface area.
When the rock is fractured subsequent to thermal alteration,
the fractured surface is extremely vitreous. The fracture
splits the grains, rather than breaking around them as in
unheated counterparts, revealing the true luster of quartz.
Since crystal boundaries are no longer interfering with the
removal of flakes, heated material fractures more like glass
than like a rock aggregate. This fact is dramatically
illustrated by the change in surface topography when viewed
by the scanning electron microscope. A color change may
occur when cherts are heated if iron is present in sufficient
quantities. Color change occurs at a lower temperature
than that effecting thermal alteration but may be used as
a valid criterion if accompanied by vitreousness.
The information gained from this study leads to
the conclusion that if flint materials are cautiously
heated for sustained periods, an alteration occurs which
confers an advantage in manufacturing chipped stone imple
ments. Furthermore, prehistoric peoples were probably well
aware of this advantage.
x


UNIVERSITY OF FLORIDA
262 08667 196 2


62
s ainp les of Oc al a chart 1 inch in length, tere- p re \ a r... :1.
One of those was heat-d to 400G and the other was kept
as an unhetcd con i:ro 1, 3ot_ cubo.inJ cored 1. jtad san--
pies had been relieved fron the oten ionodiate?.;- at the end.
of the heating pc;:ice \-r thout first being allowed to cool*
1lie sigri f ic ano e of f a :>;> p roc c dure \:i 3.1 b e e o e y a r 311 f
juter.
Arranger ants rere nade v/ith the Civil ^ oer.hr.
f apart rent at the University of florida to test the sveg:.-'
of t hase materials. fhe 0quipj;irjnt ushcl v?as a 8CO,1'00-1 b
capacity Hie hie Unit trsal tossing achi no with hydraulic:
type j o a dins end five ranges. The results arc yivr.n in
Tab 1 e 5. The cross sec t ion al are a of tiia corod s eisip 1 o s ;:: 0
st?jqcIard.1 sed to 1 inch ns foil ovs :
o
A = arr
A .7853
The fi r;u re 3 re c ul13 r y f ro, 1 th-3 c oiapre ss ive e tro.-y tk to c V ..
for b r. t c 0 m d ? s. v 1 e a v.-o r n t hen c :l vi e d 0 y -8 5 t us 2:.-
Pre 3 sir; fho foro in poun 3 of press uro pe r s quare inoh.
io another
tvTt
cored S£xp3.es of c.vSic--
i-jid f:;.g'
8rrings c tat :e rc
\;c- 1 <
h f t *, cvp r' Fa i t c t re r
o;fh f v
as O.e 1;crib ati ho0vc .
Che
s a i vole of each o.f those
:at ari ala
was bon cod to 4003G and si]ovad to coo? in the even, One
sajo;. 1 : of 0: oh v.*=e retained as ajj. urbe atoa control. fi-:-
vo1- 1 t / ; a -; 1v : n 3 n T;: b 1 9 be e kipur 12 v hic h g: : 1 h 1 c -
: 3 i y in 3 w ;_j t 1 e d a i a y¡ 10 c 0 r. t c d 1 n To c las 8 v 1? d 9.
he or >v:.r. jive how yi.-ldrl the fed 1 or? :r; rosnlf.
i>o - A .: hi- f jo in hr 3 c ?>, if is th hr...


46
If opal were present it might he a simple matter to
explain what occurs when water is driven off through heating:
the opal when dried would crack and adhere more firmly to
the microcrystals exactly as jello would tend to stick to
the side of a glass,, This might result in a binding of the
microcrystals. The presence of opal as interstitial mate
rial in chert, however, has been quite thoroughly dismissed
(Folk and Weaver 1952; Schmalz I960). Attempts to detect
the presence of opal in this study produced only negative
results.
Despite the discouraging comments thus far, the loss
of water which occurs when cherts are heated is a very
significant factor in the alteration of the rock. With the
removal of the intercrystalline water, the microcrystals be
come firmly cemented. Thus when a fracture occurs it passes
through rather than around the individual crystals In
other words, the stone breaks more like glass than a rock
aggregate even though the same microcrystalline structure
and texture are still present. This, in turn, explains
the increase in vitreousness of the fractured surface.
Chert is composed of microcrystals which constitute the
mineral phase known as chalcedony. Mineralogically, chal
cedony is waxy or greasy in luster but individual faces of
this mineral are normally not seen because the crystals are
anhedral (no definite shape or orientation), usually sub-
equidimensional, and microscopic. Therefore, when fracture
occurs, especially if the rock is coarse grained, the


Figure 13-Composite Illustration of: (a) Compressive Strength
Testing Machine, (b) Close Up of Jig with Core in Position, and (c) Core
Split by Application of Point Tensile Load.


Vibre :u:
Tv vit..: -1 i- o re
glass or a ra: :;v nub-rtsr*:-' h; 't ..d fu: ue :oro
v i vre ous rr. ob j o ct in, I :t i h . t\: o 3 stc. . *' L ? c b ex
¡el a.? s. Tro r de r ico o c rypi/c ry a t c.I i: : '-o /, t o c on ~
vox1 t o 3; i o en ercr-o v,u.-\, 3v ore ?v acoJ. J A re .' -o ov i it A o
r e o o o or. -.-ty t o ruv. 1s o? i i: 'c- o t orre n v.. u;- : o oT o e I -C A TO0 0
( a a o re,. io i' -1 y ;;0CG"T'). /.baritina? rccvjas i" scclo
of TMorJa cov-xd not achieve or- r .cinta ir: to. xr: 'X-o; ts
h i e\ , This fact i Ten o wn b 3- tro cu,o:. i by c f t ha p o o i e ry
ro?;¡a A.r.s v/h A o 1 .Ir:oe o.te s ti- at p o ii. o 1 v:'.o f ii-e at- a trac ¡
1 cvjcr t su7orstutopronab 1 y rot oeu-r 00 (ox 10004h) *
¡Aireo the* practice of altering litl-ic materials seers to
J ii i ve o c o urre d on t re o e r cm j.c 1 e v e j s in PI or id a, it c c v.l cl
not be assured chat earlier inhabitants were caretTo of
producing tempera tare s higher tnan their descendant:-:.
Bo o idea, from pc t roer a p h 1 c an a 1 y s e s urh i c h vril 1 be de a c :c A t e 'l
latori it has been c3ei.iOnstrs.ted that the aiae of che crypto-
cry &t c Ci:: 0 o ? 3 nu b ch anjee even th oujvn vitre ous In e !:o j occara
after hi: at it ft*
FA o.Ti.' '.a or ? et s exv c 3j.e-.rc e t c :. 1: *. :;.c a A '.;; n on.?.1 o tro* a
c n 1 c o i_r a ;. i;:c d exc c p t f ox* :-;a. i- r 3- *\ dir e c tip u. .c!. i' v3 e
corle;-: v/l* ¡xh: v> -vy be r thin as 1/C i.n-.l: or as thieb -as
5 c*v : -a 1 i i icb thi s ? a Ct ~ r b o i rie c:ec <: r-1 i one 1. Oc " a:? i on-
ax J y, honev'i., the c-h-rt is sianiihj xeo.p ct- oxcooe i r ,
o.n inc!i or :;a An teA.chr>oca. V'¡ t*./it fire t,ri : r' .** <' er a::1 tidfror. c'"be:: 1 o


75
increase in energy being absorbed may have been due to an
instrumental error. Except for the absence of the peak at
112C, the rerun materials exhibited the same type of curves
as were initially observed. The sensitivity of the record-
ing galvanometer of the Soils Department had been adjusted
for the detection of the characteristic peaks of minerals
whose thermal reactions are of greater magnitude. Thus,
within the framework of tests available to this experiment,
the curves seem valid.
Petrographic Analysis
A total of 45 petrographic sections were ground to
approximately 1CV to show the internal structures of chert,
especially grain size and orientation, intergranular rela
tionships, and cracks. A careful search of the slides at
a magnification of 100X to detect evidence of differences
between heated and unheated specimens failed to reveal any
thing significant. Some of the slides suggested that heated
materials had more fractures which were more open and more
oriented. Due to the heterogeneity of chert, however, it
is hazardous to draw any conclusions from the petrographic
study other than the fact that there is no change in size
of the individual crystals or their orientation when cherts
are heated to temperatures of 350C-400C. This statement
is in agreement with the findings of Tullis (1970: 13/*i0 who
reports that Dover flint even when subjected to axial compres
sion revealed no preferred orientation when loaded at 400C
under a differential stress of 3 for 20 minutes.


59
(.40%) of iron. Those changing from K 6,5 (between light
gray and medium light gray) to 5 H 7/2 (between grayish
pink and pale red) contained 2500 ppm (.25%). Those ex
hibiting no color change contained 1100 ppm (.11%). It
should be emphasized that:
1. Color change occurs only because of the oxidation
of iron and will not occur if no iron is present.
Many samples of Florida materials did not change
color.
2. The temperature at which color change occurs
(240C-260C) is not synchronous with the change
to vitreous luster in Florida materials
ca 350C-400C for sustained periods.
5. Therefore, color change cannot be used as a reliable
criterion (at least for Florida cherts) in ascer
taining if materials recovered from archaeological
sites have been intentionally thermally altered.
But if a combination of vitreousness and color
change occur frequently on artifacts or waste
flakes as is the case in Florida, the assumption
that man was subjecting the chert to temperatures
sufficiently high to cause a change prior to final
chipping is valid.
Strength Tests
Preparation of the Samples
Uniform-sized samples were prepared in order to
determine, by standard rock mechanics tests, whether any
differences in compressive and point tensile strength exist
between heated and unheated specimens.
Initially, twelve 1-inch cubes were prepared, each
weighing approximately 42 grams. Using a diamond blade, it
was necessary to saw the stone as accurately as possible to
the desired dimensions and then laboriously grind the sam
ples to exactly one inch. Any deviation would have rendered
the results unreliable. Since this method was extremely


TABLE OF CONTENTS
ACKNOWLEDGMENTS ii
LIST OF TABLES v
LIST OF FIGURES vi
ABSTRACT viii
INTRODUCTION 1
LITERATURE REVIEW . 5
Exposure of Flint to Fire as an Aid in the
Chipping Process ....... .... 7
Use of Fire in Quarrying Operations 10
Caches 13
Discussion 15
MATERIALS 18
METHODOLOGY 22
Heating Experiments 23
Weight Loss 23
Decrepitation and Explosion 34
Vitreousness 40
Discussion ........ 43
Iron Content of Florida Chert 57
Strength Tests 59
Preparation of the Samples 59
Compressive Tests ...... 60
Point Tensile Tests 66
X-Ray Diffraction Pattern 71
Differential Thermal Analysis (DTA) 71
Petrographic Analysis . ..... 75
Determination of Specific Surface Area ...... 76
Scanning Electron Microscope ........... 78
ARCHAEOLOGICAL APPLICATION 82
SUMMARY AND INTERPRETATION 87
BIBLIOGRAPHY ........ .... 92
BIOGRAPHICAL SKETCH ..... 96
iv


o' :-ron. hlhose c''anting fy-jm ]T 0,5 (b -1 ] i. .'
¡ --;y and lio di un light gray) to 5 R 7/2 (botv.'yen ran
pin k cui?. :1o y-et ) o un t: irso, T1 ::oy>-
hubitir.y fio celo i? chary- car. rained 1100 pro. ( 1lp ) It
s ho u 1 d be 2 :.:p ha o i ? o d t h a t:
x. Color chango occurs only because of viro ouidotion
o: iron and vil! not occur if no iron if; present
Ikr-'o rvu/oples of Florida rater; 1;. did noo charge
color*
2. The temperotara at rhick color eh..age occurs
(240C~2oCc,C) is not synchronous uifh th ' chongo
te vi'-, roots luster in Florida materia! s~~
c a 350 0 C;+(X 0 C 10 r su & t a ine d pai-i o us.
3* li'f;reform s celo.?1 chonga cannot he used a: a reJ irk ;
Cx i to;*' ior 1 at* 3 oamc ior J.1 cri0.u ch0ri.3) in asecr-
taining if laate rials recovered fr or:: ore hue 0 logical
sites have been in ten t i on a 11 y t h e .r nal 3 y a i t ? re Jiafc id a coLibination of vitreousnoss end color
change occur f recu.en11 y or: avtifa0 13 or v;ssh
flakes as is the case in Florida, the a~-iiL.ption
taut pp.u van: sublet int;>_ client te- ia. upe roturen
sufficiently lira to cause a change prior to final
chipping is valid*
Strength ffosto
Ito; ; ;p;.; t_? : r jof_j-he__3r poleo
Vo.iforoi-r,iced saxples rare pr<,t. orad. in order to
cl e t c r. i: - by s ones 0 rc in- ?.k ; 10 r h v.v: i c 3 t e 3 t s . he r ; e r: an.7
u :.ii e3.'en0 o c cy y r<..i ve mid p o 1 o h trr. s ie : t r 0*1 g t h :i ,.
'b & tv; 5n i v 0 t e d re d 1) n';: a t ?d 3 y. 2 0 i...- i: y..
In51 i ai 1 y, t >-t^' v e .1 in/* h cubeo v< rpner a d e o.c :
i/c in * a oxi.: toly gra.r.'S* Us in : r d: end brine-, it
-v0 ? ...0,o1 y to ;>cvf :!5.:.r".y a.y ac.cx u:< t 1 y ns por:nibl;.- to
th-- ui- rrnr-.: --:1 tb..u laboro-1 -.ly gil: i oho son-
!' to c.V'Ot': ; ii;? ;jjt- 0 'vi dir, uld V< 0 rer.do;
th; peso


vate r; O i'
JOW V
four f
0.hi> :¡ <: j
u fo ti-\: ol
kno. fl c yj r_ o c or j y
o: too u:~9 oh .Ci-v.-.i
.t;.;-'* :r i:, o: e vafe Ib 10*1
" i to ^i.-i:i.-..ve V;cn
: OCX ' (- 't¡ o V 1 y !V; I 4
y. 2 r t .i. o v "l v. t-1 y j ate; -a r- b ? nf: s ir- o 3 i i.
ar-3 p vi.-.v' hr,; o o y i is t i r v
.. L e: i a 1r a e c a i t 1 c c e t e a h i11 al o
becky.:.
knr j:-; s. i y y c a v o; 10 e h e a o cu s-> .i . ; .in:; :u < i t r c / :t =!*.
sperrradc proov.. c= por.oa .Iono 1 lo t.?.h;i% 1 arya
ch.tpp.'.i fiatto. a\ O'V.i, etc* hr.vs knar:, r-vpo;rein ths
liter:i v.' v i :e d t'1: te b ¡: b e t n ¡:.\¡el- o y- s c x. 1. h b r, c r no o r a i. f;
v/hy t )->e e e re d e;; c r i t i C 11 : o -i l< c :, r j.o o J y r ?sa;:: able
to h'j peo i rhv t' ?3 lrr-t Cv;:v; deoc/Gloed .vocenL'ly by
HaL'it ;i ~V0: 3;-I) v/v.; i;sofl ' pc.I-:::Ir:ic:v: butchering
i it, Oth r s U;-:p a e ; i on e tha i: hava be :o anc :i 13:cd :.n t h..
1:! t v a tv.:: . uve v-j n v i;b, 3 [.o: ,e a i/ere ( i ) b a.vi; d o h :¡ ;* o ther
r.: o i o i ; {.< V./r it- i o h d < ib 5 tr o, 1 evo:.; ? 3 : ( h ) l\.; r. d a a
gravo y ceda* (;} v-vu?i.\. i.=h:;:: vr:; foraa to i;, ccapletod Inter.
X t t b e .70 -1 c-v.i r. 'a ia i v d ;; v t an o }: t r o rp g g c i o::: 2 o:.,o
''cachard' o-V-'ihoi br-caito Iba buriea flmln ¡va.'na tbcrr
a a i y o 1 ve r:- d ir. ordo v t o 1 e i c in al chj p , i- . p o j ;i o... . bu la
or;l a s,r: 1 ? r; t ,1: o .' o n c r i./i on a r.c; x \ v e a t i o y 7 \o ? o b
c he x o c- o i i ;! t a o e .vJ p 1: > t v t o a 81 u: 1>> c.t a fe m..-1 i *1 o ;, -
:1 n;; r. f to7.r h^> v> c.e.\at :va.t.,; va a;of ' ¡ j ?.> 1 c-' f i; n
i? no l.: :e i; i :*. x-, o a f o 1 a o v. o:p o n o t to o top b o re...:..
t >. .-11; j. o ; a X o c:;' t : v. r¡e v i c .\.i c o o f f i r*.;. Tho.te f e r i 1
i i ib o r o- f 't.v :ib c :. o i i : p 7 :l. : 1 : 1 r,y t i\ x : ib 11 .e
^ ; xtiv. *... a ¡ o o 1 a-. . la . ib -. i:;i. 5- -o,.:.. i a Vv ca-'.t-' r y


84
Vitreousness may not be completely reliable however.
Several broken specimens were selected from preceramic
levels (>2000 BC) of a site (A-356) in Florida. These
specimens were chosen because their outer surfaces were
extremely lustrous and some exhibited a pinkish cast. It
was suspected that all had been thermally altered. Small
flakes were pressed from each specimen. One specimen which
had an especially greasy luster on its outer surface was
very difficult to flake and the freshly flaked surface
was dull. This was a disappointing development, because
it was hoped that by removing chips from field specimens,
it might be determined that vitrification which penetrated
the entire mass of test materials is a permanent change and
might be useful for archaeological interpretation especially
if local outcrop materials are not naturally vitreous. This
specimen had either patinated subsequent to thermal altera
tion resulting in a replacement of the internal luster, or
soil conditions due to long burial had operated to form the
greasy luster on the outer surface. The former explanation
is more plausible because often materials that are not
lustrous will be recovered from the same location as
lustrous materials. If soil conditions were responsible
for the luster, then all specimens should be affected.
In examining a representative sample of flaking
debris or artifacts that are suspected of being altered,
an investigator should find a number of specimens which
exhibit a relict dull area surrounded by extreme vitreaus-
ness. This situation suggests that the dull area has not


14
Montgomery County, New York: . a cache of 117
arrowpoints on the farm of . near a spring.
They lay about 6 inches below the surface, on a bed
of ashes 3 inches thick, which rested on a hearth or
fireplace, about 10 feet square, of cobblestones from
the drift. The arrowpoints average about 3 inches in
length and are of dark-blue and gray flint, leaf-shaped
(Wilson 1897: 971).
Old fort and village site in Saline County, Missouri:
Three feet farther from the center was the edge of a
pit 5 feet in depth and 6 feet in diameter. At one
point on the bottom was a pile of minute flint chips
scaled off in making implements of small size or
delicate finish; there were enough of these to fill a
pint cup. A slightly smaller quantity of similar chips
lay higher up (Fowke 1910: 90).
Dutchess County, New York: While employed in digging,
his spade brought up a number of arrow-points. He
described them to be nicely piled side by side, edge
wise, in two or three rows. There were perhaps two or
three hundred in all. On each side and on top were
some charred logs and sticks, that seemed to be the
remains of an old fire. They were 10 or 15 inches below
the surface of the pond. They are of a blue jaspery
flint, and seem to be in an unfinished condition. I
thought that probably the Indians had brought them
from a distance (as I have never found any of the same
rock anywhere in this neighborhood) and made this
pocket and covered the traces of them by building a
fire, intending to return and finish them at their
leisure; or, perhaps, they hid them there to prevent
their capture by their enemies (Shepard 1877: 307-8).
In 1894, Dr. J. F. Snyder excavated Mound No. 1 of the
Baehr Group, on the west side of the Illinois River,
thirteen miles below Beardstown, and opposite the mouth
of Indian Creek [Illinois]: At the base of the mound
was an oval of clay on which "was a mass of black horn-
stone implements, that apparently had been thrown down
in lots of 6 to 20, with sand over and between each lot,
as though to isolate them from each other. This deposit
of 6,199 flints was covered with a stratum of clay,
10 inches in thickness; and on this a fire had been
maintained for some time .... The flints forming
the nucleus of this mound are very . rudely fashioned;
some are quite neatly finished, but the greater part
of them are only chipped and ill-shaped. they
do seem to be unused blanks (Ellis 1940b: 112).
It is interesting to note that most of these accounts
mention charcoal and the unfinished condition of the finds.


11
Holmes (1919s 176-7) quotes Fowke in a similar
description of the use of fire discovered in another pit
at Flint Ridge, then adds
In general, however, the action of fire is destruc
tive to stone, and if not very discreetly employed
will so flaw the stone as to make it unfit for most
uses. Fowke tells us how this destructive tendency
was probably avoided by the ancient quarrymen of Flint
Ridge. According to his determination, fire was built
upon the surface of the flint body, such portions of
the purer stone as were desired for use being protected
from the action of the heat by layers of moist clay
(Holmes 1919: 364).
At the novaculite quarries near Hot Springs, Arkansas
which are possibly as extensive as those of Flint Ridge, Ohio
Holmes (1919: 198) observed some use of fire in the quarrying
operations.
Ellis (1940a: 45) describes an experiment conducted
by William G. Mills at Flint Ridge which may cast some doubt
on the use of fire in quarrying operations:
"... here was the bed of flint uncovered and an
abundance of dry wood at hand. The fire was kindled,
and was kept burning for two hours, producing an in
tense heat on the underlying surface of the flint.
The fire was then removed and two buckets of cold
water were thrown upon the surface. I fully expected
the flint to break in large pieces, but it merely
checked and cracked into small pieces to the depth of
perhaps half an inch. After the conclusion of this
experiment it was apparent that fire as a direct agent
in quarrying of flint was perhaps not effective."
The following account of Indian jasper mines in the
Lehigh Hills of Pennsylvania is interesting because it hints
at the possible use of fire to fracture stone in a manner
similar to the historic observances described in the previous
category:
Scattered fragments of charcoal were scarce in
shaft 12 below the ninth foot, but all the other
diggings and dumps were sprinkled thick with bits of


32
TABLE 4
HEATING EXPERIMENT CONDUCTED TO DETERMINE DIFFERENCES IN
HEATED AND UNHEATED SPECIMENS AFTER SOAKING FOR ONE MONTH
Sample
Wt Loss after 24 hr
at 100G .
(%)a (%r
Additional Wt Loss after
24 hr at 350G
(%)c
Ah
.42
.38
.18
Ah
.40
.37
.12
As
.91
.79
.32
Eh
1.08
.40
.03
Eh
1.29
.51
.03
Es
.89
.43
.16
Fh
.50
.47
.03
Fh
.22
.16
.17
Fs
.61
.57
.27
Hh
.86
.74
.08
Hh
1.07
.65
.35
Hs
1.00
.79
.25
Nh
.53
.47
.05
Nh
.57
.49
.04
Ns
.65
.54
.23
Th
.55
.47
.08
Th
.49
.45
.10
Ts
.87
.77
.55
Calculated from weight of samples 24 hours after
removal from moist sand bath.
^Calculated from weight of samples four days after
removal from moist sand bath.
cWhile there appears to be a slight, yet unreliable
tendency for the weight loss to be greater at 100G for the
unheated soaked samples, the greater weight loss is quite
consistent for the unheated soaked samples between 100C
through 350C. Because there is overlap in percentages be
tween heated and unheated depending on the sample involved,
this method, while consistent within samples,could not be
used as an archaeological application. Even if the investi
gator had a profound knowledge of the materials with which
he was dealing the results would be tenuous.


observance of the phenomenon of thermal alteration stimulated
the undertaking of this study. During the summer of 1969
I attended a four-week Flintworking Session conducted by
Mr. Crabtree at Shoshone Falls, Idaho. This session was
sponsored by Idaho State University with funds granted by
the National Science Foundation. Hr. Crabtree's encourage
ment and suggestions through personal conversations at that
time as well as subsequent written communications have been
invaluable. Dr. F. ¥. Zettler of the Plant Pathology
Department at the University of Florida, who gave so generously
of his time in helping me with the photographs, but whose
real contribution was his enthusiasm which is more infectious
than he realizes. Dr. H. K. Brooks of the Geology Department
without whose help this project could not have proceeded
beyond an idea. No phase of this study was undertaken or
completed without his physical and mental participation.
Lastly, I would like to thank the members of my
family for their patience since 1964.
iii


Figure 4.Explosion Resulting from Too Rapid Exposure to
Heat (note "potlids" and blocky angular flakes).


jSd.id.
i-36
1910
Giltdri, K.
i 9o?
HAi :¡ ..-dil,
1970
iOLi ,2'i,
1B95
1919
K&KP09,
1969
f.uiSu.
1966
r.y-'t i-
es?
95
, 1, ..i,! '..i afi.r-:> *i l'1 '' i17 _u'.
A study of the .trior,' .na Ce:, o: i ; of Chert,
An eric en Journal of 1'.. lore.-? Yol. 2'jO, tv:.. 496-
3TC. he',; haven,
,:/. A;
Stone Art. ?h: rt ;'qt i.h ,vrl ho not of the
Bureau of .. a viaitheolrr, for the gears
Tu'Jip97 l\'7-\r;8, Washington.
Antiquities of Central and Southeastern Hissouri,
Bureau cf Ansuioea Bthnoloyjy, Bulletin, i-'o. 57-
Washington.
V,'.
ruarte at. Irene eraierred. Crier. to ties: Broduced.
by annealing. Science, Yol, 1579 nerteiater 2i,
up, 1444-?. Washington.
birlLSli' H.
A 1-alec Indian Butcherlr:- Kit, Anericrr .Iris ouity,
Vol. 55¡ ho, 2, pp. 141-4. Sal l! lt
!. E.
Stone Implements of the lotovac-Sneeaasolee
Tidewater Province. fifteenth Annual Threeet
a tw a-i: i.3. FB. .
Washington.
KancUjool; of Aboriginal /nteritan Antiquities,
Part 1. Introductory'tbs iithic Industries,
Bureau of American Ithr.olory Bulletin, Bo, 60.
Washington',
Fiiiis: aks arilsjiisciin rjiL-a-Bsoi;
On the Significance of finrset i s on Stone
Objects Concernir Fracture Feehaiiltn, Glas-
tcubnische Berichtc, Vol, P2, at. 1C, pp. 45t-'iG,
Pr.a'nV. uact Am Pain. i In C-ean3
, x.vio stata ,;y gAsfe&|s
A Study of guar' da. Band Gruir Surface We; tuner
with the Spanning lectro Aierv'ooge. Trcno-
action:: of the _Fev; yGarW Ac: r -a y c f Sciences,
pe. 57-7/. 'Jew lo.vh,
i .0, the! opy
1. eriicric:
a,a a,- ,
da a vara aic harping of Iracta
Bulletin of the Ge;
Vo:r.8c7V't5rTo7ri
On- th '.jori in -1 in r, \A-1 n t n o f the Ar c1 r r
in 1 .nc. Tv f r>f; th ..nthno cl- ' :1


jor re-
47
fractured suri ace is dull due to refraction tur
flectti.ua. A ft-or he :it;> ny > the fractured surf"ca is vitreous
duo to the grn tor ur anr-.if amioc of 3 iyr t ;h c \ occure when
V ie ;Pr &c ture -posses + raue h sue ce s siv e r icroc r;rs t s 1 s an d
i o t a r c i ty s t f!. r> aces reveal in j t Vie in t r ? g res vti a r n a tu re o f
querta.
If the j .; a r e r i J. i s fi n c g ec i 'no d t I t 3 c : .-. f o a 11 e r
s? i 11 y faster ;i iich l.ay be V- c v use e v cn thcv rh i 1 c. :n t r, s
the sane overall amount of '..-ter, there is lees moisture
t e:1 nr.; r '-novecl f ron eny given in tersti l;i ul aro o Ti)ere s a o/.s
to be no correlation betv.von crystal ai as unci tbs Imr.rrs-
turn a t v:hich r.l x e rati on oc c urs :l ' hi or: dc 1: a r c c Tv -
love seen tc be some correlation betv/oun too eoj ¡yor. i tier of
the chert and the length of pice as roll the tc.'.y;-atvi.;
at urie.ii alteration occurs,, t'ho fact that crinr c-orts
are formed as limestone royiscomenjs v;ediscussed in the
section on Hater inis, dome cf the mt or:..vis to seed ryj oarer'
to : ifict dxiferently than others in that they did not
r a r. v u v t u ho same t e my e rat nr : s or t i r . a p e rio d s ; al s c t ho j
did ., .'1 dee w-r:l t-J; :. or explot Except for the area directly
ur'v- 1i1e or*tcx v:hi r h a1vr. :. = tr he vsr~j sil .1 ceovs
a 3a Id :f ao i or / e hangc- aid rx c t oc cu v .u j r. ej :re c Vj. a t tV:e
te cic.(. t;i;,yer11iiO s v; :i.c n u1;/ e f fcc t vd a r ' c c yo,
Ifietamerraturo£-- <;rc :¡i.; i= .;l sic aly 1 3 ft at
either 130 C or afO-'O a change occurs ifioh. I a veuy o uparen
'hvrt' the sample i s sub o g q u o i; t i y f 1 akc j rc v c r 1 trig a v .11 r c o v. j
X ' f u r o d a r rface. In a do i :,i on it j s d e f hi i V -o I y o r.;;; i o r t c
j->aru f:-ic tvro ^ tc1!r i; ^? cnO'" t " ( * v Y~- -v C r ) TI? t :f v;t


non-
51
needed to tx*. ¡ns:Torra j c.ro cry-; tal line struetur
crystalline fon.., the v i trii i eat ion which ocouj.-s v;hen rl in b
materials are heated to onl; 558 0 -ust hr. accounted .for in
another way.
The i.purities in flints generally act as fluxes,
due to eutectic development?- . ,
. i;iOp0v was found ir ;il I flints vary in.; fres
0*0? to 0 12 "per cent* V/hilc iron 1 s ob jec I,-iorrnle
as an ira pur i ty b o c au se of it s cl i s c oil c r in, j effect s,
the small percent^e present in the flints woo! cl
probebl:*1 be of nc significance in a body censos it ion,
Seme of the American flints are free from Cab* and
oil e rs contain goner illy lea a t h an the Fro nc h 11 into.
iIoss on ipnit: oa va r3 es fron 0,15 to 0.85 Pe r c en t
md represents CO., dissociated from OaCC;,, end ad-
s o :?b e d o r c h "j r. i c JX1, r a o i ib i ?.o b. w o i o r (Pr c dnl r* ui d
Sheerer 1920: 292-
It the impurities (or comb in'it ion a of impurities) contained
in Florida cherts are serving as fluxes (substances pro
moting fusion) to fuse a thin surface film of the rvpc-
cryst?;ls, then change will occur when the n.elting eoint
temperatures for these impurities arc reached (eutectic
dc-vo 1 oprcat). If thi r, is the caso-, anr,-rers are fourd for
two plural5Jip* problems: (1) why vitrification occurs at
c u c h a 1 o v* i cu o e r a 11: / c (150 c C ) and ( 2 ) why s one lx tori a 1 s
do mot respond at the same temperatures-the molting points
of tba Mux; s are probab 1 y cifh;r!'P 1 ' the percent-?pe
of calc inn is quite hijh, this also erpi.;ias rhy coruain
Lurte via Is do not n.ahe a do sir oble o tur. ge de spit:.- i;lo
ta r j £ r a L u r e or I e n *; t' t . j f ti t c he a t in . p oi..j C a I c i urn v.d I J.
serve as a flu:; if pr-j-ont in i-r.alll quantities, but ere-
v o Vi i s fc 3 o da;' j r e* d re'! c 15. on f r o n can- nr r A: p j f a r J : *r, c qe r:. .i 11 a, Tur eo /Jor 1J eh : ;:\vl cl; re a; or ud


19
Chert, being a rock, varies greatly in its physical
characteristics even though the basic components, the minute
crystals of quartz, are uniform in character. The factors
that determine the physical properties of cherts are:
(1) the size of the quartz crystals; (2) how the anhedral
crystals fit together affecting porosity and fracture;
(3) the amount of foreign material present, fossil replace
ments, and other heterogeneities including flux compounds;
(4) void spaces; and (5) crystalline fabric (the crystals
are not equidimensional or always randomly oriented). Thus,
in the Florida cherts, there are different types and even a
single nodule is not necessarily homogeneous throughout its
mass.
The lithic raw materials used almost exclusively in
this study were Florida cherts. Justifications for using a
general term such as chert are as follows. To this author,
at least, the term flint indicates an extremely fine-grained
material found in the chalks of England. Also, as stated
above, flint is used as a common designator for artifacts
with no specific material intended. Using the modifier
Florida preceding the word chert calls to mind a particular
type of material much as Arkansas novaculite, Pennsylvania
jasper, or English flint does. Though there is a range of
differing textures and homogeneities, Florida cherts were all
formed under similar conditions and share common character
istics which distinguish them from other siliceous rocks.
There are a number of conditions under which chert
will form. Florida cherts occur as a secondary formation due


,'n-: 2 ad
firply ce,.lent to mic roer;/ate 7; ^' :a
to appro xi ir--i bel y a re due ti. -a 1" rtronrjth rvceaeary to
fractu r-o 10 o r i d a c he r t s u r d o r p o in t '; ensile i o na, n ap r re::
l r t o i y s GG-' r a i. u c i' i or in t he i 11i e re; n ui t : s o v .h¡ c -. ar c- a
h'hGi the roed lo fractured eubsecuer. :j to l };: r ;-¡l altcrau) o¡u
che ir actUi1 3C £ur f. sca :i o e::l.roi\o7.y vi t re c . .* , V..ia c tu:: j
splits the j:c*c'.:..; > rather than break:; re, oreara rv.ac i.n
i nhe a L"a c o a- c l\: . r o a 4 ro v o c 7. ir r t h o ox uo 1 v. c c r oq u11 e
S ince c ry s t a i 1: o unda. r i o a ar e no 2 oe.; r 5. n t o r fer i: > 'V i. r
re-oval o i'lakoa 5 beate 1 at?ri¡?i 5 r.>cturoo :oorc .1 i::o .1 ac
than ].i>6 a rock arareyate. This facu is cra¡r'.ti erd i y
illustrated o the cirineo in -- in-fl c--upe-.par.hy fv-':-oi5 vio. o:1.
*&y tbo ocaijair ; el actron aicrcr oo; c 1 co1 o r chroa-;c r .r
occur vd*."u charts are he atoa : f Iron is pro s-:-at la cu.m cica
quentiba oa, Col o' cheayo occurs :-rc Aovar tenva. v.a.cr
t h ur t h: t ao c t i.i *:; t}' erar .1 a 11 r. r a t i o z i h v t va y b o a: a o
a v al i c! c r i r ari o: j i f ac c oiz a1 j i r d c y v i i: i- : ou s i e s,
The 5.n f o r j a t i o r. c ai n o C fr c 3 a hi ~ s t v o y ] c d / t o
the c o a c j us : n t h at i f f 1 i r. u n a t o r 5. ?, jo aro c .-a-1 i o us 1 y
he e i e d i o y c a o t a i j' o i o e r i o c s o: i ?. 1 ! ortica o o o u r 51 \ ''. i c h
ccrl sra r/n aivanlv. '. ir:, .'.anufacturiny chippo i ctone ir. I-
::.O':i.v, Vi.r-tliernorc- ^ pro riot orle pocplas ver prchahj^
j.1 o f t Ij i a a <1 v aa l,


/
y
v
Opal, Pure

Chert, Cob

asoa Lake
Chert, Joh
¡son Lake- Pre.
eatc
Chert. Hig
i Springs, Oiigc
oer g
c
FI irt, Erg
.ish
- -- ,r
Chert Cea
.
Obsidian
0 l
SC
0 ?
Degrees Cei
i
DO 400 30
itigrade
600
Figure
jial.ysis


73
Ocala chert, English flint, and obsidian. Arrangements
were made with the Soils Department at the University of
Florida to use the differential thermal analysis equipment.
The results of this experiment were encouraging since they
substantiated data obtained from the weight loss experi
ment. As the sample takes on energy (heat), water is
driven off. This was apparent by the endothermic peaks at
112C as shown in Figure 15 for opal, Johnson Lake chert
not previously heated, Ocala chert, and English flint.
This was due to the removal of the adsorbed water held on
the surfaces of the microcrystals. In the pure quartz sam
ple, the already heated chert sample, the High Springs chert
sample, and obsidian there is no peak at 112C. These mate
rials have already been devolatilized or there is no moisture
to drive off. The only anomaly that seems to exist is that
the chert from High Springs which is Oligocene in age did
not show a peak at 112C. This material is more coarsely
crystalline than much of other Florida material. This fact
is borne out by the quartz peak at 573C occurring with this
sample and the pure quartz sample. This peak represents the
alpha-beta change in the crystal lattice, and it is immediate
as the sharp peak indicates. This inversion reaction is
reversible in heating and cooling.
To check the validity of the endothermic trend be
ginning about 350C-400C (see Figure 15) additional samples
were prepared and tested as before. These materials were
rerun to determine if the endothermic trend indicating an


15
This is exactly what one would expect if these "caches" con
sisted of preforms to he thermally altered prior to final
chipping. There would be no reason why they couldnt be
left for extended periods until needed. Perhaps they were
never recovered by their owners because European introduction
of iron and/or disruption of the aboriginal way of life
intervened.
Discussion
In addition to the references cited there are other
accounts tantalizingly suggestive of thermal alteration of
rocks used to make projectile points. It is tempting to
interpret these descriptions as evidence of heat treating
simply because it would be rewarding to discover an accurate
account:; however, they must be considered conjectural until
proved otherwise. This might be accomplished by reexamining
cache collections as well as conducting excavations with
this problem specifically in mind.
It is possible that pertinent publications may have
been overlooked (many were not available), but it is unlikely
that there exists anywhere in early documents the step by
step procedure involved in thermally altering siliceous
materials under controlled conditions. Several authors, most
of whom have already been quoted, consistently mentioned the
use of fire. A summary f this information might be as fol
lows :
These processes [of shaping] are distinguished by
such terms as breaking, flaking, . All are purely
mechanical; none are chemical, save a possible use of
fire to induce changes in the rock in some parts of
the quarry work (Holmes 1895: 25).


>0
to the re; *1 ac e lo n t of c a a- '> ona7, e s w i t h o i *1 i c s. Al 1 o f t Vie
chert deposits in Florida :-.ro in rea Li on ship to relict clay
hi 11 s in o on t ac t v;it h linea ton; the mo generally c orre si.'1 ond
to the Oca!a irch v;here si? 1 oe<:>_dopositc 11 0 unconfori¡
ably over the Ocal : lix?oio;vcr Cherts also occur at the
edyo of the arch vic.rc 11 cestones are intexceedcA with
ci!icecus de ?ozit ihe cc, cur r? nt;e of cLer :a i3 thas in 1-hr;
up p e r part o f fch e lio c o no Coal a Linn s t one, and the 01 iy c c 0z ie
and Lower hioc-er..s Ferrari one bordering the areas of the
Ocala Uplift* Chert t fciuid on the Ocela Arc h have replaced
j iraofa tones that are Loco.no in ays and those such as occur in
lo mando and Hil i Ac o ro O o un t i o s h ave realc ed 1 A r e r to :a~ 0
that are Olicocene and Loner Li00ene in ayo Cherts in the
Ijioeone deposits are found as far sooth as Zulpho Springs,
liare eo vounty* There arc no cherts zu.iu rally outcropping
along the east coach of Florida or in south Florida (Lrooirs*
personal c wu¡ ¡unicat i on ), Figure 1 shoves the ex ten b of the
are al d i s i:; \i but.i on o f r or rr. 31 ions t h at r,. j.g Jrt c on t a in cha r t
in pon Vi £ u 1 a r Fl or i d a.


69
were heated to JOOG and 350C left for 24 hours, and then
removed immediately from the oven
The results of these tests are given in Table 10.
In all samples except obsidian for which the data were not
consistent, there is an increasing reduction in strength
with increase in temperature. In addition, though admittedly
the data are scant, there is an even greater increase in
reduction in strength when heated samples are removed
immediately from the hot oven.
If a comparison is made between the results obtained
for compressive tests with those for point tensile, a dis
crepancy seems to exist. Under compressive strength when
samples are allowed to cool in the oven they resist failure
longer than unheated controls. The results of point ten
sile tests, however, revealed a significant reduction in the
time and load necessary for failure to occur in heated samples
regardless of whether they were removed from the oven while
hot or allowed to cool in the oven. This seeming paradox
is easily explained. The binding of the microcrystals which
occurs when the rock is heated adds compressive strength
through cohesion to the structure. The increase in homo
geneity which increases strength under compression is the
very factor which descreases point tensile strength: (1) the
individual microcrystals are bound more firmly together;
(2) therefore, when the flaw is introduced which is pre
liminary to and necessary for fracture to occur; (5) failure
takes place more readily because the specimen fractures more
like glass than a rock aggregate. The added decrease in


INTRODUCTION
A recent publication (Crabtree and Butler 1964)
suggested that prehistoric man may have found it advantage
ous to thermally alter his lithic raw materials prior to
manufacture or final completion of chipped stone implements.
Subsequent examination of chipped stone tools as well as of
waste flakes recovered from archaeological sites led to the
speculation that this technique had been employed aborigin
ally in the state of Florida. Florida materials often
exhibit the pinkish cast and vitreous luster felt to be
indicative of thermal alteration and differ markedly from
the siliceous materials found in outcrops.
Since the summer of 1968, the author has studied
the collections of stone tools in the Florida State Museum.
Specimens from every Florida county are represented but
samples are scarce from counties where there are no natural
outcrops of chert, e.g., south Florida. Waste flakes were
not available since they had been discarded. For several
years, however, the Department of Anthropology at the
University of Florida has been storing all stone materials
recovered, including chipping debris. This debitage was
also examined. This extensive search has led to the deduc
tion that the original speculation was valid, i.e., many of
the chipped stone remains appear to have been thermally
1


57
influence when attempting to predict fracture Therefore,
the more glass-like the material, the more predictable the
fracture. Heated cherts are more glass-like and fractures
are not only more predictable but easier to execute.
Iron Gontent of Florida Chert
The incorporation into chert formations of concen
trations of iron which impart a pink to red color upon
heating is usually because of secondary enrichment resulting
from the mobility of iron in iron-rich paleosoils or bog
deposits. In some of the Lower Miocene deposits, however,
another situation exists in which iron seems to have been
incorporated at the time of silicification which resulted
in the chert formation. In addition, although they are
rare, bright pink colors (ca 5 R 7/4) (Munsell 1946) are
sometimes found in cherts imbedded in terra rossa residual
soils on Ocala Limestone. These cherts are dull or earthy
in appearance and do not resemble cherts which have been
thermally altered (H. K. Brooks, personal communication).
Color change takes place between 240C and 260C
in Florida cherts. Figure 10 illustrates the variation
which results depending upon the amount of iron present
in the sample. Unfortunately, true color representation
was not attained but an analysis of the iron content (see
samples in Figure 10b) revealed that samples changing from
10 YR 6.5/2 (between very pale orange and pale yellowish
brown but nearer the latter) to 10 R 4/4 (between pale
reddish brown and dark reddish brown) contained 4000 ppm


89
temperature was. This would be almost as ridiculous as
saying that he had no conception of time because he hadnt
invented the watch. Besides, these investigations demon
strated that, at least for Florida cherts, temperatures
between 350C and 600G (a range of approximately 500F)
would effect a desirable alteration in the material. That
is, as long as the elevation of temperature was gradual,
there was no increased ease of chipping at 60CC over that
of 350C. While there is no apparent increase in flaking
ease, however, quite often attempts to chip flint materials
that had been heated to 500C-600C or had been heated to
350C-400C and removed immediately from the hot oven,
resulted in a lateral snap due to end shock. Thus, there
is additional strength loss with increased temperatures or
increased stress. This fact was supported by point tensile
strength tests. Below 300C a satisfactory change did not
occur in Florida cherts. Materials were not tested above
600C (approximately 1100F) because the aborigines probably
could not reach or sustain such high temperatures.
It remains to determine if the three major problems
to be investigated in this study have been successfully
solved.
1. A desirable change does occur when Florida cherts
are thermally altered resulting in a stone that is easier to
flake than its unheated counterpart. No structural change
occurs in that the size, shape, and orientation of the
individual microcrystals remain the same, but through the
removal of interstitial water, the microcrystals are fitted


i.uc.r. .30 .in energy boirabsorbo } ' r- a c.v. to an
instru'.3Rtal error. Except for the absence of the peal:
112e,J, the rerun matc.ri1 s exhibited the some typo of curves
a s v.'eiv in j t i a 11 y ob served. The sens! t i v i by a f r he reco rd-
ir^ gea.l variometer cf the Soils Departs one had boon adjusted
for the Ctec 1;ion cf the cb j.racteristic reaha of r ircra 1 s
i ose thcr *.al rose tions are of groate a0grita .9, Chi;:
\' i h;) in the f r or a. c nhc of tort s ava i 1. ab i a b c t nia e xp e r in-: r. 0 v
the curves cm. 11 valid*
A total c.f AS petrographic sectionc vero ground to
approximatel y lOp to shov; the internal struet.res cf chart,
especially grain size and orientation, intergranular re 1 -a~
fio.jshi'. and cracks. A careful search of ice slices at
a nogr:;1 fie01ior. of 1 CCA to detect evidencc. of diffc-roncee
bet'.-;a.:n heated and unheated specimens failed to reveal any
thing siptificont. 8one of the slides sirga2sted that hooted
' u b 2r 01 & h a d m o re f r ac t uros v;h i c h wo re c o r 0 open ?r more
orient..-'. Du to tro heterogeneity of chert, however, it
is hs:r. Cou- to Griv any conclusions fj'01.1 l ho petreprap?ic
st.1 y a":.r bher thi, f ;ict i;hat the re is no cher>3o 1 n size
o r t hr. ;:. : i v h m. 1 c ry.: i ; 1 r c r th e 1 r o r 5. t. n C t i o n 1 ;hen c he r t s
a;. ; n :.: -1 ' d I. :. t n_..or-1 u r.. c of f SC 0 C 400 0 C l7-is s t a temen t
?:? in r. -ern.h -dth the firdi/pe of Tul 13s. (19?0: who
rop0!:tr t ;P. /- :? f 1r t ev0n 1:: 12 sub j jcted to axial coup: e;
si on rv-vu.l-:' r ;vv;ferrc.d eric-if. .s'-ion when loaded of 400" C
v c. e r a c f u b i. I t" v. ;. o f ;. ?i for 20 niru.it e n v


61
Figure 11.Composite Illustration of: (a) Drill Fress,
b) Corematic Diamond Core Bit, and (c) a Chert Nodule with
ores Removed to be Used for Strength Tests.


S
difierenfly when hoato W'.--S subnltted to the Soils S: > rf~
seiit at le 7hiv ai o i florida i o i ioric Atsai ,'tic:
Spoetrophotosetor ana?¡.sis, The rosi.ts o thio analysis
are given in Sable ?, It is not Itnovm whet jicrcertage of
calcina is necessary to prevent the desires reaction lot
it Is interesting; to note that Coal;; chert and Hint Springs
chord had conn:; he rib Ip hiph.rr percentage# of calc inn than
the t'.-jo Johnson Lake specimens. The Ocala and High SHgrt&g
ctorts consistently reacted differently loor: Johnson Lelo
and other ilorida aateriais tested in that the expected
chango did not occur within the saro tei.oecaccro and tine
ronce s (
Figures 7* 8, and 9 illustrate various types of
firoic taros. iPigur* 7 s hov;s an exarcp 1 e of a potl id i r ac ture
vjhich occurred only when the Materials vene heated t<..o
rapidly. Figure 8 ohev/s the type of fractured surface
which often occurred when the samples vero removed frea a
hot oven to a cool environment. The specimens in Figures ?
end 8 have broken with a corohoidal fracture typical of
flit at mate rials. Figure 9 is a thinning flake; intention*-
el 3 :j s t r? ick f r o m an oh s .< i n c ca -c ; In add i t ixi t e th 3
conchoids: fracture, this lust speci¡m*n poa^ossoc a v;ell~
c fir. e d b u lb o f v s rc u r. r i cn n c t pro a cut in Fir mx- s v a nc 8.
Figure 9 as a re: infer a bat :i laicrocystall *e rock
v:ll 1 brack vrLth a cone"ride 1 fracture hut no bulb of per-
cussio : will i? f.-vadotf; lv.Ixx jmget r. -s vahe-n place,
T _c ro.ud t a o.' t h e 'na ¡ tin' c x r J: x n te f> t ib 1 ish
unite cl :: F: IFxt c .x.t 1 F.x k:_i.a u .v- be .* disturbio,.


79
electron be ait: the technique &o> s not eliminate or ere; '
any additional cur face features" (Xr ins ley one! Ii erg olio
1958: 458). Heated and taino a ted samples included silicified
coral, Ocala chert, High Springs chert, and fino and coax so
grained John sen Lake chert, The specimens ae-i/s placed in
a Cambridge Stereoscan electron microscope horsed in the
hcprix't- .cnt of Metallurgy on the University of PI or id. a Corpus,
T:;e eui:ire irr clured surface of each of thoae opecincurs \-c>s
scanned. Tip.urces 17 and 18 shew the typical surface topog-
ravd.-y, dramatically illustrating; the c hen pcs which occur
V'bon cherts are heated. Pi pure 17 is of Johnson Lake
crnrt (100OX); Xip1; re 1C is of silioiiiea corv.l (12,200X) .
In the unh.cated spec: .oi:c., the individual grains are seen
looking like so rimy broad crumbs. Some fracturing has
occurred throe pi: the individual grains but more frequently
the i'ractux-c a;oes around the grains. In the heated spaci-
1 isV:f., th5 fr:. cturos pas3 thr ough most of the indiviuual
grona; that is, Vo individual grains sre- actually split,
and the frac tures, continue on passing through the inter-
15 : -l- rr^.¡s vhic: 1 v.re now v.ore f irnly cen.0nted In othcr
v." h.; *v'fracture ocoor*; it alternately splits and
ijfsos t hr.':. h succor'dins crystals end in tere rye tal areas
5 n its rail ur.til it t jrui nates. This accounts for the
smooth surface ir. the h..aloe! specimens,


55
Figure 8.Examples of a "Crenated"
Fracture which Often Occurred when Specimens
Were Removed Directly from a Hot Oven to a
Cool Environment.


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Decrease in Coaprcasive
Strength
Increase in Compressive
Strength
Ocala Chert
Silicificd Coral
Obsidian X
High Springs Chert
Obsidian Y
-a
_
!
&
*r-
btr
cr
J L
i£r
0
(%)
43
5o
figure 12.recrease or Increase in Compressive Strength over Uoho-ated
Controls of Heated Specioons; Samples Shoving a .Oncreese Had Been Sea-oved
Isced lately from a hot Oven ahilo .Samples Showing an Increase Had Been Cooled
before Removal.


21
Figure 1.Areal Distribution of Outcrops Probably
Containing Chert in Peninsular Florida (Adapted from Cook
19^5> Plate 1; Brooks, unpublished geologic map of Florida).


66
both, of these specimens as obsidian based on certain arbi
trary attributes shared by both; the use of other attributes
may have resulted in a different category for each. Of sig
nificance here is the reversal of the amount of pressure needed
for fracturing the material depending on whether the rock was
removed from a hot oven or was first allowed to gradually
cool in the oven.
Point Tensile Tests
A jig was machined to apply stress to the cores as
described by Heichmuth (1963). This jig was used in connec
tion with the Siehle Universal testing machine described
previously. The jig was constructed to apply point tensile
load to the curved surface of the cylindrically cored speci
men with the long axis of the specimen placed horizontally
and at right angles to the loading jig. The jig was con
structed so that the point compressive loads were applied
through small diameter steel hardened dowel pins with rollers
manufactured by Holo-Krome of West Hartford, Connecticut
(see Figure 13). The cones of percussion induced at the
points of application of compression produce internal tensile
stresses perpendicular to the load axis.
Cored samples, one inch in diameter of varying
lengths were prepared as described earlier. In the first
experiment, two cored specimens of Ocala chert were heated
to 400C for 24 hours and removed immediately from the hot
oven at the end of the heating period; two samples were
retained as unheated controls. The results of this


16
It may be concluded, therefore, that Crabtree
made a significant and original contribution with his ob
servation, experimentation, and description of this phenoim
enon,
I first discovered the thermal treatment when I
was about 17. I would find worked aboriginal material
of superb quality, but when I found the raw material
source it was never the same and had an entirely dif
ferent texture. I finally wondered if they had in
some way treated the stone and so tried the old coal
range and heated the rocks which I buried in sand.
After much trial and error, I was able to duplicate
the texture of the worked pieces and decided this
was what they must have done. I could get no one to
accept the theory, however, until the Les Eyzies
conference in 1964. Tixier accepted it readily as
he had encountered the same complex problem in Algeria
(Crabtree 1969* personal communication).
Since 1964, many archaeologists throughout the New and Old
Worlds are beginning to suspect that much of the stone re
mains recovered from archaeological sites has been subjected
to thermal treatment.
Since the Literature Review has revealed no accurate
early description relative to this problem that might be
applied to archaeological finds, at least a portion of the
major contribution aimed at in this investigation seems to
have failed, i.e., it should be possible to demonstrate that
prehistoric peoples were aware of the advantages conferred
by thermally altering their lithic materials. However,
enough accounts exist describing the use of fire in some
phase of the manufacture of flint tools that the evidence
cannot be considered entirely negative. It is not surprising
that accurate accounts do not exist when it is taken into
consideration that:


c;.u}iest! con-
15
Tbi.i is fci.,ac11 y v; nat or?y '.oul ;c 1 5.:r ta c- 1:
is ted ox v-re forms to he then.:.. iy jittered rete to final
obippiufi. 'there would he no r;-*s:/n atp they cculci t he
left Jot extended periods? until a-,:?i. %*;'¡aps they aere
never recovered by their osona.n eecsue auroptaa iatredue tie.,
of iron and/or ¡ii.erur.ticn oJ the s.bc.eigi.^1 way of life
interne;: 3d .
Blscaesjon
In addition to tie references cited there are oiler
acco'. "it tnrtalisxngly euggfis'ive of therual alteration of
rocks used to rake proscfcile points. It is. to.ipi.infi to
interpret these cluscripf 1 sus ae evidence of heat treating,
sixply Veoauao it would be rewarding to discover an accurate
as: o cent$ however, they ierre bo considered con pec ture: jptil
proved otherwise This night be ace obit lis had by rsBXf&xniKS
cache collections as well pc car; dueliea e-.eerfvctinae v.ihh
tuis pi.Obj-.-i. speci.ticei.ly in alud.
If St r.otsi Vun that; pe.viinori orlsi leaflets stay have
teen CiiClook-ed or eg w.-rt. not avail ¡-.bio), but it is unlikely
f then? i etc enyvhers Ju early conn- o' ., the i. tep ly
step procedure Involved in thorn;J 1; ; Iboeirr; s5J.i300u.-5
rateriJr- under eontrollrl eenditjon . Several authors, .post
of whet, t .-vc already beer- quoted. consistently ner.tior-ed tie
use of fire, a suhdimv of this irti\vri.t30n uigbt be as fol~
1 ove.
'itone processes fo£ .- hpoingj i n-, ciistin; >..is'u 1 by
such terns as forsaking, flakin''| . .111 ax v.jioly
is oh icol : none are chai?. san-; aoosiM e use o"
fire 6; in*we charger, in f: : esc:-, ie ..... s y..it of
the Cue..:; 'I (bo1. rf; ; 1 j ,


^UNIVERSITY OF FLORIDA
^ 3 1262 08552 IIP


48
is not based entirely on intuition (see section on Strength
Tests). It remains to he explained, however, why it is that
if the temperature is raised too rapidly, explosion occurs.
The original weight loss at 100G is due to the removal of
adsorbed water held on the surfaces of the individual micro-
crystals. After this initial large water loss, the weight
remains quite stable until 350C. Prior to this, the tem
perature probably has not been high enough to remove the
chemically bound water held in the intercrystalline areas.
I suspect that the following happens: 350C is probably a
sufficiently high temperature for alteration to take place
if this temperature is sustained for a long period of time
(see Table 6). If the temperature is raised to 400C prior
to the gradual removal of the chemically bound water, ex
plosion results because the alteration proceeds too rapidly.
Vitrification is always evident, at least to some extent, on
the fractured surfaces which result from these explosions.
Therefore, some change must occur almost immediately when a
critical temperature is reached even though the material
blows up at the same time. There does not seem to be any
previous study dealing with this problem adequately.
Preston (1926) in his article on the rupture of glass dis
cusses the fact that glass will fracture when alternately
subjected to heat and cold. But his work mostly describes
the type of fracture which will occur depending on the stress
to which the material is subjected. Perhaps the answer lies
in the following statement:


urce3dure was followed for 150Gi 200G, ato' so or chro' .^h
bOOC but it was now felt necessary to subject the specimens
to v.uch long periods of hoar, or to reheat them at each suc
ceeding bo aparatare since no additional significant 'weight
lens occurred with. prolonged he cting or sub sequent boating
at che same tenterature. (Tdu-; validity of this procc-i.r.
i:> os too 1 ished v*hen the next e vneri nont is da:: c ii : d, } who
recul ts of this experi'-;ent are giv:in Tab 1 e 3.
Twenty-six specimens consisting of from
14 c he :c b n o du 3 e s ob t a ine d X r o i.*¡ v ar i o us are a o o f Ki <" mi a a
plus one specimen of English flint v:ere ghod ho atoo,
i a we i p;ho dreheat e cL, an 6 i-ewe i ghe d ag a in t rom ;i s r r. c ? s c \
temperatures to 50CC in the fell owing v/a.y. Alter the
initial weighing, the samples wore heated at 1C0C for thour
lite" which they were removed from the oven v'w.io hot, mlwood
i mod into 3 y in a desiccator, end re weighed when th-.c/ov. ,;h3 y
coo3 They -wore returned, to the oven and epain hunted to
3 O') 0 i or on add: hi on a 1 ly he v. re and sub.j e c t e d to be : an1 j
p i -o.,: w u:' o as d o s c r it e 1 ab c v::, ihi s p i o ca s s v;a s repeated
u;:.v1.p0Cc C 1 .::s ;'acho0 j he ov:.w wa b _ e;¡ co costir,g
t c o r:. t u v : t f 0 M b :i n c re me n t f1 I o i t at o c h :L r, o w?me n J" c r
1 ' our, 71 a v j i :.n n ove cl u j j I n c >t h e r v. s 4 i ; o o at i
s -.c: i l v. n wi h our f o re no h o no 1: ru c c o c. ? :i. np t o ¡ *;:. r a t ure The
o:;3. y vr i. o t i on v/p.ic h o c eu ura- vj ? 1 x h 3 .u th o c >" pe;'iw.nv. v.-; <.r
ti'; 1 i!: ,is v- >t- cor aioer*od :iccon;';;y to u>- ;j"c.t I:**>:.atc'icl
to a f v 1 c-pt'5 houws t c vch towpc*r j 1:uro a13d hoe:i done
at iLO'b-C, bfc f-ict that no sl"!W;ric?nL t chiiticfovl weight
.1 ow, oo cu rr. t-(. r WU-^bir _; at wo mo to..; .wulw hiwt'if.i1-
ir.; at


12
charcoal. About; P.C cop c- \t c- -the- eh3.053 ; nd 10 or
cant o f the 1rye blocks re redd a. > a:-' if by fire ,
while reddened fra.:merits viere abundant it all the
fire-places, k'o'citing v/a- cnroi- than hat fire had
p 1 ayo d a great p ar t in the o u 2. rry in g p r o cees ; bu i wh i 1 a
four fire-places examined phewed no trace of cooking,
they 100 gave no sure clue to the it purpose, and thora
would have r:;mined 3 doubt whet or the fires lr-A not
beer built for uaruih hud not a .fifth hen th die--
C!;v:tsd in shaft 2, at a depth of ip feat, seeded to
y v. 1 ; 1 e ihe q 12* s t i un. X t v;os an O v en r-o :v..-. ? r-j y )> Lrj 2. t
cf a 1 h;.:p of ja roer and coni; aired a a ass of charcoal
srl &s: :cn iho fact that the sides of the blocks weva-
re 0 5e : c d an sevc re.2. i a cl 1.1 -c c 1 y s. -lit t hr o nr; h th 2
itj i d 11? ;h i 1 t'no i. tr r: tices vTu0. f ?J. Ie a wi c;} 1 ;' ine
sp). inters, offered conclusive evidence 'list clio quarry-
r.'.r. had built- the fire to frac lure the blocks 1 which
a an red ?. feet, 1-1/2 feet, 6 and ? inches respec-
tir J'v in disasteri
i \y 0 ;e 1: ts provec (a) that i f a lar;ye* blcok
10 ro * rhJ y h c at e d o c
nere ns pieces at a mc-d.er-ito
v;euv s re rr t r 0 f 110 & re
ents '.Lose the i?' original
luster, hov.'evox*, acemo tf
lr clay, cu vas ndice .
of two foot in dieteter is
wood fire it brinks into rx
bl o., (b) that only the fir
podd n-- d: ( c.} that the i'rL;
gloss V/ the process. The
be rayeined by leap burl:;.3
by the nigh-;o3 i sherd fr-rotor a of r,ora>~> of the rode, v.
c hips fc uu d on th e fire 01 r. c h ; I'ore ovo r* tv n :y o f l he.
v-vrked forks gathered or the 0or-face had been prcbe'fy
i i re-re dd o no , an ' it s net. un 1 ike 1 y l ha t the In d ian
could bow sc n :;: d the b] ocks as to eoech the r u vo
ports without seui? irv.. the whole-, vhil 7*1 of
largo end coa.cs- blocks si.-giit heve tear* f:>.ic-fractured
to t;:ot tie]e o!: t ; f vhe i-y ( ?ic rc e 2' ISr-)A : S-';6 ),
Cakl oy (1 f6 2 pern or. a), cs-ouuicaiion) cays "I have
ecir-c acroos evioenoc at several localities suggesting that
rton:. age crafvauien sOi. uti^u-s ootcxiiied finkeH ci :I n trac tab 3 c
stone by uniur hit vothed o'" :ftrv netting,1 . Also
A.r k.*-.usklip on the coott cv. vt ..< f the- Cepe kaninaula,
Soul): A/rica-, cros.ioi? cl ye at n<.c revealed a Late
Achpoli^: factory sato. it the base of large blocks
of fui 1hr.vrfc?.?v i'n- b. v;. 2V'txui:.:;; t'wouyh the
r.r.-sc -¡lor? cri pranritie;a cf 1: rye tf.u;:rnal flakes,
en d o a fch f a u.r r c r. .; '. r.;: <. . i:- j a r i- a round sur f ac j the j'e
ax1? a c'j bruV/.in or :.".cr., v: i-iul or.es and cleavers
raw- tv., suck fluir, k v err A. tk I. Good1.;in has
auggr::t-. 1 fv. x s c'r nMan r...rv c vtairv i ihe fiekes by
the v-f 'fir .- vkk k. ', that iv 0 say burning
ii-v-n -?ourd i' .; '.'look.:- 01 .¡undstorio and then dashing



PAGE 1

)CL1S FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI ICUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCI'S FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC XUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC 3CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC )CUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOCUS FOC

PAGE 2

:icns Gonc6)rnin{;; the Theriiu-j. Alt^ j.)OGTC.i: 01? -ALAUoCiAA,

PAGE 3

'ERSITY OF FLORIDA 3 1262 08552 4725

PAGE 4

This study could not Lave "boon uiidertakcn cv BivccesGfully coLiplcted i7ithout the cooperation of Eia^iy peopl-:^ v/ith varying scientific back^ri-ounds v:ho contriciitecl their ki-i-fwledge, tiiae, aiid equipiaent. This type of i'^ite./aiscipliriary approach is incressinrcily iir^i^ortant ar; specic^liaation bocones a necessity in an extreiaej.y coKpl-f:x v;orld. The author v;isheo to express appreciation to tho> i)cp^;rt,J9nt 01 Ketallur£,5? for '.iakinr it possible to use -.no Sc?^:riing Tilectron Kicro^^copo^ fche Civil iringine^ring Denor^ti.ient foi' the use of their eqL)ip.c.ent :u.'d for astiistir;?; i^irh the rock Kechantcy tests: the Soils rep.:i.rt;;ient for th-^ uae of their ov^nsfor assisting I'ith differential ther-n^l pnalysis, and for conducting; the atcuic Gpectrophcr:;;-teic^nalysis; the Geolo::y Department for assir;tinp uith ee^^'"graphlc enalysio, deter;uination of surface areri and peoosi of Florida cherts, and for peraittin^; e::tei'dod u^o of thei o'-cn] the nenbcrs of :;iy dupervisory GoTn;:;ittee , ea.;eciaJ]y Dr, Crna-les P. iPirbonks, for sufv^esting -mo approvina of theoe investie.ationK and for editorial aceistancc. 'Hhcxc v.r-'e en, pert ;\r.:ej..d; . . ! i '; fj.nd conpl'rGion of resesjrc:! projects overwheliiinr or a ; ' ' •. , .^.i : :..,,::^:^ ; / ' '/ r:rateful to; h la, .' .. . . . iberley, Iciah'j, e

PAGE 5

observance of the phenornenon of theriP^Q alteration stinulatecl the unQertakin;-: of this stuey. During the siir.imer of 1969, I atteiTdecl a four-v.'eek Flintvorkin^'Session conducred bj Ur. Grabtrse at Shoshone Falls, Idaho. This session v/as sponsored by Idaho .State University v/ith funds --ranted by trie National Science Foundation. Tlr. Crabtree's encourau;ement and Bur-gestions through personal conversations at that time as i^ell as subsequent v;ritten couirjjinications ?Lave been invaluac'le . Dr. ?. V:. Zettler of the i'lant PatacJ 0;j;y Depart i-u'^nt at the University of Florida, v/ho save so £:enei'Ousl; of his tine in helpinr ne with the photoTr^phs , but v:hose real contribution v/as his enthusiasir. uliich is ziore infectious than he realises. Dr, H. K, Brooks of the Cieology Dopartrent v;ithout v/hose help this project could nol have proceeded beyond an idea. No phase of this study vas luidertakcn or completed v/ithout IjIs physical and mental partic:.::ation. Lastly, I vculd like to thank the nenbers of ay family for their patience since 196'^!-.

PAGE 6

.13? 01'' TaBLIiS 1, lleatiTip; E^rpsriaont to Eote/':.iinc V/oight I:or;3 of 1-Incri Giibes ........,,.,., ?"? 2. neixtlnc^ Experinont tc Det:;ri:dno \^c±p^t Loz?. oi Sa^iipJeE irom jjiffcront Locatjloa'^ ,_.,,.... 2y 'j>, Uesiilt^ of E'roerinont GoTiductod to Detei'ia^riv^ Ability of Heated itock Sainples tc u'a"-^; Or; Koistueo ,,,,,,. c ...,...,. c ,. . VO ^i„ Ileotinp; Experinent GondiictGd to Detendne DiffoPGnces in Heated aiid Unheatcd Gpociricno AiCtcr coakiny for One Konth .,,,,..,,.. 3>? !;>» Hoati);'']\;x:perirnGnt Conducted to jjo tox-Mne ',;oi.-^.;:Lor^s of Archneolosical Specimens SiiScecto.j ^'f Havin^C Beon Thersially Altered .....,.«,., 55 6. H'^at Sc&kin^; Bxperiiiient Conducted bo ,::-cert^jn Lenf^th of Tii^e lleceGsary to Siioct T•,or}J^;:1l Alteration ^i2 7. Results of Ato.nic Absorption opoci:rop'-.c/^:oi:^.{:ti/rAnalj.'si;-: ,.,« ........ * ?1> 8. Ke3u.j.ts of Curcpresi^ivG Strouyth [Tr^s';*^; Waen Rooted Specir-.e.in Arj ficb.jectsd re b Coo3, Envircninont While di;i] 1 Hot . ^ ,,...,.« . b^ 9. HcoiOts of Go:-:: rL'j:-; vo o!;:?on^;th ';?ests W'lian ;]oc-i;«d 10, Iterniltn 01 Point Tensile StronGth

PAGE 7

TAELK OF CONTEIvTS ACKlJO-/L:^]X}i-;HI;T;:v ..,,... 'l LIST OP i'i;>UR^S vi ABS'Ti^AGI' .,....,..........'. viii IKT:iODUCTJCN ...., o .,-...... o....» 'LITSrolTUrii RU^/i:?.-/ „....., ,,,.,. '} Exposure of Flint to J<"\r3 as ai: Aid i'j. tli:; Use of Piro in C^uarr;'in:; Cp^iai^icns ........ 10 Diocucsicr: .,,.....,..,..>...-' ^ !? IaTjI^ i-Ati."»,,.«,€»€«<•• i•••••'•*• '-'^' Heat ins "5::vperi3ientd .,,»,»»...,....,-. r^?:^ Voif^ht'Loss ..,.,,.... = >..>... ^i' Bt-crcpitaticn aiid ExpIoKio, j:A Vitreo-unness ,. ..^ ..* = ...-.»' . "^C "Jiscussioii ,,,». = » 4 o .. , .,..,. Iron Content r-f K.orid?. Chert ,,,..,.., ^ Prepaiiition of the S^-^^plcr ....,..,. Coiapresoiv.-; 'i'eots . „ .. . . . . . < « , . , Point Tenaxlo TeGts .............. X"I?aj Diffj/soticn Pattc;rn , » Differoi: t-iiu. T?terrial ^^Jielvsi::^ (i^i^^O ...-.-.. Vl Pet2";>:c,.:-^obic Aiial^yois »««,«.• ^ ...v ... . 7;> Detc;';^l2::ttion oi Spooirio 3urf«c-:.; Ar-Cia 76 Scanning; Electron Ilicroscope ..,...,..*-, 76 ARCiiA^OLGGIOAl Ai^PLIGA-ClCi'; ^ = .....,., 8,.i SuiJ'JARY AND IKTSRPRilTATXv 1 ,...,..,..,. 37 BiriLiocF;.p-iY . . . . , o , : . 9:? BICGRAHIIGAI. .:;A:v,;CH ...,.., , . , v6 '1 .5 r,'i GO

PAGE 8

UST OF FIGURJilS 1. Areal Distrlbutiors of Outcrops Prcbsbly C'Jitaininiv Chort in Peninsular Piorida ..<,'....»/',, 2i 2. Vfeiglrh Loss upon Keatin^i; cT Ghorto f-oi^ Vsriou.;; Locations in Plo2?ida 253 3. Veight Loss of" Samples of Florida Chort Iilusi;rating the T;/pical Pattern Obs-srvod TorAll Florida Speciifiens Tested Throughout a Two--Year rr.rioa .... 29 4. Explosion Res-^iltinr^ fro.Q Too Hapid Exposure to Hoc^t . ^;6 5. Results of E:;porinont Ck>ndi;cted to Toab tb? Validity Oi "Flaking'' Hot S-conos oy Driopin^v GoJid V/ater on ThOHi • f . V .'...,», V ., 7 ,...., . . ^'-';' G. Vitrocusni.ftS3 Occurring vvh.cn lloi'ida Cherts Are Heated and Sub;:;equontly iii'laked .».<,.„.,.. -;•'-!7* S>:anple of a Potlid Fract\:iro which Cftoi' Oacurrea when Plorida Cherts Were Subjected uoo Kanidly to -'lOC'^'C Tenoeratures , . , ././'... '-">-'!S, Examples of a "Cronatod'* Fracture \-:hich Often Occurrod v'hon Spccinenj;; Were Heiucved Directly fi a Hot Oven to a Cool IvavironioOn!., . . ^ , , \ . 9. Specinian Depicting Intentional Fractuj^e v;ith Bulb of PercusGiGn and Typical Fractured Surface Eiiiphasizin^; that luipact HiS Cccurred 10, Heated Specir;:ens and Ujiheated Gontrola lllusfcratiin:; jJegree of Color Chan;_^e .DoTiending upon the Arr^ovait' of Iron Present in the Chort ,,».,,. ^ ., ,, 58 11. Composite Illustration of: (a) Drill Irosa, (b) Coro:aatic Diaxr;ond Gore Bit, and (c) a Chert Kodule with Gores Penoved to Be Uacd for Strength TcotSc . = .,.,.., 61 1?. Docreauo or Iiicr-onse in Comoressive StrexTp-th over Uaheated Controls of Heated Specimena ."'...... O'-'r 1^. Composite Illustration of; (a) CcMpressive Srron;:th Teatin;^ Kgchinc, (b) Close Up of Jin; i\/ith Core in Position, and (c) Core Solit'b>Analication of

PAGE 9

3A, X-Hay Diffraction Pattern Illustratin^j that r^o Ohenr.e Occi'.rs in the Ci-ystal Lattice when Florida ChertQ Arc Subjected to Critical Teiaperyturos . . . 15. Re3u3t3 01 Difforenbial Thermal Analysis IG, I'etrorjraphic Sections Showing No Detectable Change in heated tg Uiihoated Florida Ghorb , „ . o , . . 17. Surface Topocraphy of Unhsatod and Heated Oohnson La.ke Cher't Saiiiples as Yievred by the Scanning Electron Microscope ..«.*».«...:•.;*», 18. Surface Topography of Unheated and Heated oilicifi.ed " Coral fror:; i'lorida as Vx&v;od by tne Scr nninj: Electron Kicroscope ............ ^ .., . 19. Spec3nen3 frcT^i the Unrversity of Florida Collections Sho^vin^l: Dull Areas Kot Flaked Subsequent to Thermal Alteration Surrounded by Sxtreric Vitreoupness in Areas that Have Been Flaked after Alteration . , . 8'S

PAGE 10

Abstract of Dissertation Presented to bhs Graduote Council of tl:& Universit^^ of T'lorida in Partial Fiufilliient of the ii;ec-!;'iro";ent3 for the Degree of Doctor of Philosophy INlfJjiSTIGATIONS COriGS^riUIKG TlIE THSaKlL ALT:i:iA.^iv:OI^ OP SILICA }',T1aERALS: Aja ASOIIAEOLCGIGAL APPAO/GH Barbora J'oxa Piirdy llpx-ch, j9?1 Chairman: Charles HA Pairfcaru-:.s Jiajor Lepartneut ; Arithi'opolocy A reo(;nt piiPl J.cati on (Crabtr;^'? aAo Butle;^ 19oA) su£;v:ests that prehistoric lufin may h.'.v« found it ed/antcxx^'GU£; to thcP'ri^ially altc-r 1 ithic ru:-; laatej/iid.p prior to L-aav^ fac ture or final ccnTplotion of chippod ytoiio iir^ploLicnts* The specific otgectivsa of this re;;Garch cuid the cc^r. elusions reached are as follovs: 1, Pc estaojieh v;hethor a funotionally desirable chaiipa in (Aisrt cccuro v/hen it i~ ?i\ib^ecnod to t^eat, JCy:perinionto v/ero co;":lucted to detemii/io the tsr^p'cratai-o aiio, leitpth of tiii'.e nccoscaaj to effect the detectabla ; hyclcal alterations. Ilofftod an:] unhealed Florida chertc vere otud. by petroaraphd.c anaiyois, x-ray diffraction, diffurential therviol analyais, ;:c-avaJii£; elcotx-on rd-croocope, a;;onic spect;:^ophor;oter aiiaJyain, standard rocA ir!ech;-'nica to:A;^ aiid the yoa ub;;a.)r::tion surfoca a3n>a anc porooity technique 2,, Po davcrijino \vhaiA;er priiiLii; ivo pi'ople^: ";if:;ht hiave bea.n o.v.-.ar'^"' of the advca^ta "coo coyilcvrod by thcri'iaPly altoriny litiiic ^ate^;ial3. A revie-/ of the lii;ai-A-are raved '• a -^ '>.;.,. .-ietely adequote account dei^crioJr' / '. techniaa . :.-corda o: A-. ". , .• a, "•• :'-

PAGE 11

concl'^sion tiiyc fij.-e was used soJijetiiries ir conjimcrion v;ith iithic tecbnolory* An exanination of archaeologiccil ohip[^i/:udebriG revoalorl that a portion of l;his debits^;'.; h-do. buf;?! ini;ej'tionally flaked after aciatinp;^ The flaked rjv.rfact-o £.i--e luo L^rou.3 and differ in tliis respect iron outcrop snr.p3.es c.f rhe ^;tiuc ii.&ter5.alSs The flakes also h^jvc boloi; oi porci:f:3ion in-dicatin;:; that impact has taken place* EiJ.ba of percussion are not present v;hen rocks explode froK. -ukeriii'G Etrosaea tbouph the aonchoidal fracture t;-pica3 of flint iPa^ericls is evident. 3« To reco:f;::;.end a fcechnioTiG V;kick nirht be emploped by arcaaeologists to detcrraine whether the ohippeci stone reriains recovered frou sites had been therr.aliy alte::ed, Fio practical standardi'^ed test v/aa discOYcrec, Ho';ever. iro;;! a-J exarninaticn cf a repre-sent'itl^.^o sain-le of flrskinc; debris .J an investigator shonld find a nunbei'of epeci\nenc exnibitinp a relict dull area aurronnded by areas of hiph Ina uor. f'hia aituatien aaron^ly su£;reste thai; the duliJ area hsu not ^c/een flaked aubaequent to heatincv, v;hereo.3 the vitreous area has been flai:ed» xsiaperatures cf JpC^C-^l-OO^O are e^;ff icier t tc alter 5'jcr:d^; cl'iertc huv x-ray diffraction patterna de'^ionatrated th.jt i*a chan^-e in the crystal lattice occurs. Thia v;aa borne ont by petrographic analysis i^hich sho\;ed no chanpe in the shai-e, ai^^e, or orientation of the niorocrya'.als. The alterati.oa is due, at these low te;uperatures , to the presenct; of Ir^anAj^ities in the rock servint^ as flioies t..^

PAGE 12

firmly cenent t-'G juicrocrj'stal. r^ of quai-o':: . This fvyion led to apT;roxii;''rbcly a ^!-5>u reductior; in i-bronsth rioces^ar;? to fractU7:-e l''lorida cherts under point i;erisile loyd, ?nd appro::: aatoly a GOVo rciduction in the intorn;r-:"..uul&r Gurfcice areo. V/h.en the rock is fractured subsecUL^iil; to tli/^r^^^al alterai;;! oa, the fractured eurfaco is e:-:traaoly vitreous. u;he fj:'aGturs splits t!ie ;;;rai.a;^; , rather than breaking around uho;.. ac in iiaheatod coLiiitorv>artSi rovealiBr: tha orue Irster of qujjtz. Since crystal houndariei:; are no lo:.^;-:-r int'irfex'ii^r; ••^j t-tie rei^LOval of riakos, neated matoi^ial fracturon more liho -^lacs than liho a rock an;greyate. Thin fact; is drairiatically illufjtrated hy the cnange in surface fcopc:};raphy ^vhon viev/ed by the Gcaaninr eloctron i:.icrcacope, A color chanfce nay occur v:hon cliorta are heated if ii-on is orosont in cufficicv!' quantitiaa. Color chan
PAGE 13

INTHO DUG TICS A recent puT-lication (Cr-afytroo and Dutlei1964) suf,gested thoo pre^'iiGtoric nan i:iay ha'^'e J;'ou2-(d it aciVTint^fjieouf^ to thei-naily alter hie lithic raw i;:aterials prior to nsnurc.ctui-e or final cc;:i;.:letl on of chipped Gtone ii'iplerif/i^tr^. Subseo"ucr;t exaiuinati.on of r'hi:;;ped btone toolr: as x/ell a? of v'cstc ri3^:es recovered froi^ aro!iaoolo;/;ioal yites led to the 5!;^^:Culation t}ic.t thio teclmiquo had booi. ei,,plo2^ed aboriijincll;^^ in tl'io tt:j.tc of riOj'-J.da. Florida r^aterialc often cxnihit ohe pinkisi^ cast and vitrecua luGtor f eli t to he indic£-tiv.? o:' th.ernc.1 aibsration and differ laorkedly fi'o,;; thvj riliccoiH:; n-aterials found in cutcrors. Specir.o>is fro:.i ^-/Torjr Plcrida counby are x-enrcacntcd hv-.t ae::apjes are Gcarco froin counties v>)'hore there ore no natural ou'ucrcpo or c^;;i-t, o^S>. oovith Florida., '/j-.^ta fl?^,ke3 vere not av^,ilal;lo since they had been di:^carded, r^or -^overal Univorol uy of Florida has been ??torin?;: all cit-r.e .nc.terial3 recovered^ inclnding chippin;^ debris, ?hirdebit;'.;.'-^-^ alBo ex5i;:inod... This extensivo search has led to the deduction that the oriv;;:nnl j'pecclation vv&y valid, i.;-;., inany of the chipped s'jone renain;~ appear to have been ; "ly 1

PAGE 14

cilt-ered. The nuriber raight be 07'£-'tl:; xn^vof.seci if it were knrnvn whether patinated specineuu o;e cpeciuicns recovered from under the water had bc-e?) cubjectc^d to hnat^ Fati-ation as veil .If roinorala Trof-ont in ?loride Inkan. ri.vers, and ^prin;-;.^ cauiro chanjieD vvh: ch co:':oc^ul i;h'3 cri{;insl te:/:ture cf chert^ loakiii,' it iEipooribic: t-;> aeto^'-"irie (at present) if theriaal alteration has t^hen plaoc . The Gbjectivee o:C t/i:i research t};e.i undertaken vvore : 1. To estsfblisli Mhethev a iv.^-lloii.^}li.j desirable change in the chert occ-ars wher it is tborr^allj rJtered. The e:':porirerts coriductoA are descxiboi in the cecticn 0:1 l:'-ethoc'olozy v;bicn enbodicy rhe ?T;a-k>r portion of this disoert^tiort . 2» To deinonstrate '•/heblior prehistoric pocplo-:: :if\h1; have been avrare of the f.dvcntagos coni&ri'ed by thci-iiial3 palterinp their lithic riaterial^. To aia m this endeavor, ?tj ^r'tcnsive and extsn^ive s';arch ci exi;;tirp public at icrB Vifae mdert;v.hv:n* The resulto of this seai-ch are dericribod in the iA.thvv.tvre Hoviev;. irho Vise of annj-^^zy i-^ irtorpre i^ing; archaeologicil d3.t?"In its juost irersral sen?:o ... if-ans^vyiuS any belief about aonobserved behavtor hy rofcrral to observed behavior which i?! tnoufrht to bo rolo'-o^t" (A>:;chor 19CM : 517). Unfortu-yately . h3.3toric accounts \!cre not found vmich j;.ccuratolp descrubed ;;he procay^ of therr,U'l altero.tion , Rovje-vor, crouph descriptionrj of the use of fire durirn; so:no str-f^o oT stouo tool inD-Tufacturc \/orv; ^uiocr/Ci'^d \:,o -,;;^i.v;.ut *dic co.iclusi or.

PAGE 15

tliaithe "observed behavj.or" vroiild hc-vo been "jvo.levant "' i-o the probieri beinp; invectigated i.f the obt-f^rvei/S hc:d paid Tjore attention to detail and i:;ad provid-cd a more thorough de-cription. In addition, in the section on i:ethodolo:-.;;^', co!;jparisono are made bet.;een nateriels tliat heve been Intenticnall;/ subiecte^ to heat I'uder contxoil?;d conditiojis e^nd siibsequently flaked ;;ith. sau-ples exliibiting potlid xrsctiiroi" \--hero heat hac been applied suddenly, o^g., through forest rir<:f;< Othor typ':;s of fr^ctuj?o ro^ultinj, fro;.: Gxpansj.on and coritiv^ction ara noted. This analysis Eorvad as a re;ninder th-;^ i; fl:'nt aateriaj G iiay break v;ith a conchoidal fracture but that no bulb of percuGsion v;ill be present unJeso ii-;pacc has taken place. The arciiaeolcgical debitage sur-pected of be;ii'2; intentionally heated does poaooHs bulba of percuG&ion, •'oOjA;.tiov;s to atiy probl erj cr-e at best approxijjiations orrived at "'o'^i the oliiaination of thoeo least likely" (Aschor ISbl ; t'--'j')'' Ik. this cas3j archaool0o:5 cej. reicains V^ave provided clues to p.vebi;.^toric practice^. throu^l: systematic el! ia-inatioa of alternative solutions, 'rhe hypothecis that heat vrae used hy aboriginal peoples to alter l?thic rav/ ^nateriols prior to firal manufacture of cbipped atone tools i:-, ntren^tbened by (1) histor; accountav (2) experiiaontation w^tb. and atvidy of int;entional vs uniiHient j.onal fractured aurfaces, (3) coi^iparisons between outcrop and site :;r!afcerials , ('! ) heatln{-!; c,xperii:ient£ vith outcro.D 'jiaterials j'^esultinf; in specijnenr. v7hof3e appearraace

PAGE 16

reseaib3.es artifacoual remains ^ and (5) t(Vyts deiaonctratinc, that thermally altered "silj vo^^ous materials are easier to .fl.xke. 5. To suggest a tdcht-lq-ue v;ijich night be asiplojed by archaeolo{jist3 tc dcl^crraine j.f the chipped st^-ne regains recovered irom archaeological sit:eG had been thermally altered. Thio presupposes that the alteration is a permanent one readilj ascertained by siab^ectinn; the nateriai to so);;c yorl. of standard test. This problem 'Xp. discussed in the sectioij on Archaeolor'-ical Applj cation.

PAGE 17

lJ^'}:ER^'mlm i^iJVIZW FolJ.ovTixip; CraDtres and Butler's (lS&''i ) ci-ticlG, archive ologiso!^ beiAaii to lock for Indicritj.onf: of alteration by heat of matorialp \}p,ed. in raakin^ chipped stono lr:;ple:iant3. It novj appears that \:h±s phsnonenon is vi^ry widespread* ialGsionov-iof: J and advoiiturj^rn; "svere very poor Gthj:'Clo^;i«ts , it ::>f;ei;;ou. ^.u-rprisi/ig that th:i g techi.ique had net beexi ohsci-YGd and doGcribe^c j^jaorican Iiidiaiia, as well as othe:^ prir-iitiv;pr-oplea 3:001010. the v:orld, readily perceivoci the ad";"c;ntai,joy of Jron tools which were intpoducGd to the:c tarcnpp: Europfjan contact. Tl'Sy '.vi] lii:j[;;ly put a':h.de Tioarly tv'o Qillica ye&r^ of stoneyorkiap tcchnolof^y, often vdthi.i a sinJi;Ii r:aaor:^tion. hnfortv-natoly , very ]iai;le attention v;a3 devotod to the r^aterial or praatJcal aaj, octa r-.r T-'--"'-;^.t niidle of tb^ v:d,;;otoontn ocntixry, abori^jinal practiooa had be&n disoont.ini'Od tiiat a rapid attempt to racoad thcae praaticcs v;a";^ \u\6.:irt-'k&r} , In soiae cases 5 thi.s atta'upt caae too lata. For obvioua raasoas, therefore, it vras rioccaaax'y to turn to ninotaorth cciitiary sources alTno^:t entirely^ Thi.g, literature, uViioh in noGt fields of endeavor has oe^n laid to rest, v;as revie;^;ed in sn attempt to fdied cone. 1-Jght on a recent observation of man's uast behavioral patta--. 1.0 01 .laaj.^vu a lie anv.:..;. taa t ant 11 r^.nxiy

PAGE 18

Many excellent accounts exist of r.borisinal stone-worl'in.r; tecrmiques. In addition, nuinero-os experinental ntudies Iiav3 boon conducted and reported 'upon v;Iiich dGKc.ributhe step oy step jnanufactujre of toolG by diiec t porcu^-^ion, i;. direct porcuGsion. pressui'et and vai'ious coxi.binRtions o£ these methods. Those techniques constituted the Esjjor processes amployed in shaping una finiahinrv stone tools « The author does not v^ish to give the isipressi on that it vvas always necessary to them,-.lly alter lithic materialGo ^3oiae iiuterials probably needed no altej^aticn .. Mor is it felt thot fire \:e.s used in shaping;;. But it is thought that fire ofi-en played an important role in making the mechanical p.ivDcesses less difiCicult during some stan^^ of Eirurafacture prior to final retoucii. Holmes (1919) coivipiled a su^ciiiary voluine entitled Aborip-'i-nal American Pntiauitie&_, the sourcces foi;v:bich are nearly all pre-twer.tieth century as s perusal of the bibliography indicates. This book served as i. sprinr,board to the past since Chapter XXaV' is entitled "?ire ?'racture frocess'' and contains a nurdjcr of us3ful references' nuose of wfvich were available, in turn, led to others,IIan:>" of these early publications were not o;\railabIo., Des::ito the fact that ooif;plete coverer^e was not possible, it soon becaiue apparent thrit nan's vise of fii-o j.n connection wj.th his chipped stone tool-r.akins technology fell into three "ain catet:ories: (1) exposure of fJ.int to fixe as an aid in the chippins^ m quarry In;;; operations, (3) each-:

PAGE 19

Exposure _ of I;liiit to Fire .a^ an This categoi'T deals priir'n?,!!^' v;ith firsthand accoimts or, perbsp? more accurately, fartcifiil iuterpretationG of ri:'^«thand. accounts. It Sf^eras apprupriatG to ):;'entioo tiie rollov;!::.,.^ /oilkoown description v'hxch apoears to have had itf^ prejje^is Tvit)' Ve threw a large flint wtoiie, from tv;o to six feet iij circumference, into the fire. After the stone heoarae very hot, small thin plece>^ would pop off; we seD.ected -chose piece :'-^ v.'liich v/ould require the least I'/ork to put into sjiope., o^;d picked these pieces ^iv with s stick sp3 it at the ciyl] --rhila these pieces vere vo^ry hot, v?e dropped ccj.d uater on thoov^ plaC'?o we v/ifched tothin dcv;n; tho cr3d vntar caused the spot touched to chip off.5 and in this v-ay v/e ia&da some of the keenest pointed and sharpest arrc-'s that could he fashioned out of stone (ivallace a»sJ hoatel 195?: 10:?), Thou[^,h vvidely scceT:itcd hy lay-aon, rlvo Ar^3oiAa has boor loi-aroly discredited by aost professionals. lo those vho are sophisticated in ths art of f j.intlaiappin:e •vork /culd proceed VMch faste:;:' hy usind; a porcussor or presaui-e tool-, AlorjCs this sa:-o lino, I'oli,-os (1919; i^C^^i ) cxt^s "a re:u'a:''kFible account of tVio use of fire in chippiii^^ flint implei^ients * ^ . furniclied by Thcuys ii, fraser" who vrxs inforr::ed by Chief Paul, the head of a rennarn of the i:ic--n-!ac tribe, resident on the northern coast of Nova Scotia,, that in his f.-randfathor ' s time, flint arrovv-heads v?ere made by the systciaacic application of fire and v/ater, and I sti.ll have in ':;y possessiojti an arrov/-hoad made according to the process described by

PAGE 20

8 Holj:,es (.19192 ^-S^i--^) quotes acoounts of the IJi~:s9:? IiidinKP on the eastejrn side oi the Sacramento River end of the Seri Indians of v/ePtcrn Sonora, MeMico, x;ho eiaployed esse^jtially the sayne teciiriique. It; v:ould appear that thece Eethods v;ere not actimlly nb^.orved bj the recorde^^a. Ellis (19'' Oa: ^2) favnl^h^s other Bccormts pertainir to the Ath?il)ascan use of this !:.ethod nnd describoa several experiments v;here "chipping" in thie v;aj v-a?; attempted in order to settle the question as bo v;hetho;r drippirig; water to rciaoYe flakes is fact or lajth^""Ke says; Experi^nentel attempts to duplicate th;i s fracturing techniqus have &ii0v/n it to be very -ansatisfactory. In the first place fllat e:cposed to an open flame for even a short length of time v,-ill heat through and shatter into angular frasi^.erts and tiny flalcesc The portions of the flint v;hich do not shatter -x^x-k^ be treated v;ith cold v-aror dropped froiu the end of a stick or h-^ other raeans --jxx'u little reaction, The usu.al result of the applivu:; -op p. old v/ater to hot flint is the boiling and ."c--; ;^^ -tion of the drops of v/ater. Occasionally ^: ; ; ' ^ . ::iay fly off, but their direction and position canno': be controlled, Drox'sping thoroughly heated flint into a pan of cold v^ater v;ili .-Jiinply rs-move tiny fragiaents V'/hich are broken avray by the sudden chan(;-:e in tenperature,, biit often even tuis treatment has ne';;:€tivs results. Also the flint v;hich has been G>'b ;:':': ::oc to fire is so filled v;i'h tiny firs cracks a;id v"k' surfaces of the i(j,ate:i"ia3 ao ro!p:h.ened duo to the d:.;'i' . :::.•; ci.al expansicr .:i : : '.-"p^^tals caused by the :. v:hat ixis ; e iise it to any gTViCi/,'\.. :' ' /antage in tl^^ ' -_ ,^ •:[' stone ixapleinents, Ai> exa^aiAation of thcusana^ of specimens in the nuseuin failed to indicate that fire played any part in their manafacturo (Siiis Iv'-^-Oa: '\'^) . Pono's (1930: 2^) accoiint i::: in cor^pleto a£-:ree:jient with vilis. '''An .: ' : :\ out which is described in t})e soct:i ; . ' -y v^as conducted prior to a kdCvM.e.': . ' • results v/ero identical.

PAGE 21

9 Schun.acliGi' rcpoi'ts that The rock is i'irst exposed to firs, and, after a thorough heating, r&pid-ly cooled off, v/hen it; flakes readily into sherdo of diffor-ent ciaes iroder v;ell directed blows at ii-r^ clCF.-'rago (1677 : ^^^-?). rov;£rs records the follovdn^t It vras a source of v/onder to ;ne ho>; the delicate ari^ow-heads used o.ii Woj^••ari•o^JO with their lone thin points could bo ai^i^de without ursakinr; thoia to pieces, The Yiard ['/ijo';J of northern California j-roceed in the fcllov;ing Mjone.c: Taking a piece of ^oeper, chert ^ obsidian 5 or cor.,j3icB fVint ^vliich breaks sharp-corRored and v/ith a conchoid al frrxture, they heat it in the fire 8iid then cor-.l it £;lo-y-ly, v;hich splits it in flakes (1877t 10'^), Other authors (0.3, . l^asoii 1B^7? 2?6; Powkc 1896: ly'il) j--efor to the lov/ero ead Schunscher f;ccounts but ado nothing pertinerit.; The methods cescx-ibed by Powers and 8chu':\aeher are noj;e plausible th-.ii those avov;in£ that arrov/-heads ere D;:ide by drippin;^ cold v:-iber on hot stones; hov;ever, it sbo'ild be po5j;).ted out that they are in the idnority. ^Obe above reforerLci. s constitute the totalit;y of the available inioraati c-t on this s>ibject v/ith ren;ard to Ai^ierican Indisii practices cr:'le^v. sone uiKliscovered source exists^. The ai'bhor is :bi frequeut correspoudence v/itb ::lenneth 1', 0::71ey of the British Huseuxa. Ioi\dc^i« Re vras not avaro of thj s techrique at e"^ !i ^\xi6 couj.d -lot "reooll reisding exiy u"00unt of a:iy people hoatjiip stoue before finishiue. in X)roJectiie-poi2:: t for:.i'" (Oakley 1970, persorol corananicatior ) , Aaother Europeau scl-olor, Francois ivcrdes . . c launched until he trieO heating sons flint slid then he h/ecar;e c-.'.--":'' ': ' has ixoii traced the theriiial treatraerii; ' ' . ;vi;rean {'see Hordes 1968: 1593 and both he : .; ve done extensive work on e>:periif!ental heai, ore a u L :.';_, (Crabtreo i9''jy< personal c O-'amT-Uii c a t i on ) .

PAGE 22

10 Thus J vhere appears to be irvon j.or;:=; i^ifomi, LioD from Europoau sources than frcn the I^Igw Uorld. Ko\';!^vor, the follcwi:-!^;; account concorning the .^:iic!i;r;^an Isl^ncers dehioa&trates that the tntentiorial heating oT irUcro to oauGo altoration vvas not unhv\o;ai to ccrtalr; groups in fcha Old World. Thio is even the niore interesting oince the .Ardaman Inlander!;; v;ere reported to have no knov/Iedive of hov/ to kir.dle lire. Chips and flai:os are never used jnore th^^jri cnco; i;\ lact^ several :-:-/:^^_r-~:rJ_2-:,o.^:olo^'cd in each oucii^ation^ . , , : ... ":". ,:..:. > o:;ar:.; '.I as one of the di^oios of Y,oi':'jn-i .... i:; ..^..cJVy pjr.:\;..r);ied by them, i''or xaakirjcj ch3j?s tv;o pieces of v/hite quarts ore .need'-d; the stones are not; pressed against the thi-vh, nor ore they bomid roiuid tii^htly so as to inciceaPA'i" the line of least resistanca to the "blov; of the flokeri bvit one of the pieces io first heated and afi-ervards ollov;ed to cool^ it is they^ he'^.d fisr-mly and struck at right angles vdth the other stone: by this meaixs is obtained in a fev; ,a-o.iAents a n-j.".ber of fraf:r-ents suitable for the pux-DOses above i^jcntiioneo » T . (I^an 2c.P>Z-, A paraphrssinj:;: of thic^ quotation is to bo found in. IJasoa (189;': 15? )« Tho inf oriTjati on contained in thi3 catetcor^ conies froin arc]:aeolov;icel excavations ono. observations j^sixe at quar.i:'7 sites no Donrror in opsration, c;aari-y a: '.:o^: Js that of ?av:ke ix' hia dev'crlption o<^ Tlint }^3.d[^e, Or.io-. . . . ^!h-ace?of fire v/ero pl;o.n3j viaiMe yn the ^•"^-. . >'; o\;hich the ^ .^'v: is ratural that f'lres '^''. :i. ; • ;: v.:):-in the y^ } that, vhile beaued, v: i.'-r .. :.. ...aoi-m an i ;, , .... ^-tone could r^r;p be ^rohtu 1m Cu pieces (Wilson 1897: 870).

PAGE 23

11 Ho'uaes (1919; 176-7) quotes Fovke in a Birni.T aide scjripl; ion of the UB(? of fire cllscovercd in anothex' pit at Flint Ridge, then adds In f^ensral., hoi-zever, the action oT fir^e 3.3 dest.!''ac-~ tive to stone 5 sjid if not very discrcetlj^ ejaployed Vsill so flav/ the stone as to raake it imfit for Kiost use 6. Fov;ke tells us hov; this destructive tendency was probably avoided by the eincient quarryoien of Flint Fddf:ce. According to his deterraination, fire was built •apon the nurfacs of the flint body^ such portions of the purer stone as v;ere desired for noe beinjt; protected froin bhe action of the heat by layers of inoint clay (Holmes 1919: Jo^). At the norj^culite quarries near Hot Springs, Arkansas, \^hich are poocibly as extensive as those of Flirt Itidce , Ohio, Holnies (1919: 193) observed sees use of fire ivi the q\iarryinr; operations. Ellis (Iv'iOe; A^) describes an expeririient cGnr^uci^cd by \;illiavA G< Kills ac Pllnt Ridr-e v';hicVi li'^y cast so;;ic dorbt oi! tba use of fii'e in qvrar-rying; operations: ''.„,. her.:; was the bod of flint uncovered and sn abtinda^jCG of dry vood at hand, The fire v;as kindled^ and v-as kept burriinfor tv^o hours, producing an intensa heat; on the underlyi.ng surface of the flint. The fire \;as then renoved ajid tv/o buckets of cold ^>?atar v:e2:^c thrown upon the surface. I fully sxpectei the flint to break in large pieces, but it merely checked and cracked into s^jiall pieces to the depth of perhaps half an inch. After the conclusion of this expor:a;cat it >>-as apparent that fire as a direct agent in Gu^r.-^in{; o'" flint was per}iaps t^ok effective.'' Tne follov;iriv;cccG!.sat of Tndiar jasper ::;inss in the Lehir^h Hills of Pesnaylvania is interesting because it hints at the possible use of fire x-o fracture £;tono in a manner siiriilar to the historic cbser voncen described iri the previous cc'tcrcory : ':^ ' ' S'.-coal v;ore scarce in s' ' . but all the other d:.. .... ._:. ....... . ........nod thick with bitr .->f

PAGE 24

charcoal. About 20 per cent of the clii-ps and 10 j-9r cent of the la.rce blocks were reddened as if by lire, v/liile reddened fraginents were abundant in all the fire-places. Kothing v/as surer than that fire had played a great part in the quarrying procecsluit v/hile four fire-places examined shov;ed no trace of cooking, thfc-y also gave no sure clue to their purpose; and there iJOi'ld have renained a doubt v;hethsr the fires h&d not b£;e:o built for v/ariath had not a fifth hearth dis-co/-red in shaft 2, at a depth of IS feet, seeicod to settle the question. It v/as an oven regularly built of bli"ic':s of jasoer ar.d contained a i.iass of charcoal and aoho3. The fact that the sides of the blocks were rcofeyicd, and several had already split through the KiTidlie, while the ii'terctices v;ere filled with fine spl intsrs, offered conclusive evidence that the cuarryrn^-n had built the fire to fractiire the blocks, which ' i:.';a3:!red 2 feet, 1-1/2 feet, 6 and 7 inches respectively in diameter c riy experiments proved (a) that if a lar^e block of tv;o feet in diameter is thorourchly heated on a wood fire it breaks into numerous pieces at a iCicderato blov;; (b) that only the fra^jnents ne:: ',-1.; . ; , ' that is to say burning ii;.e:'; ..:^'ourd t^e ::]ook:; o; .i;;ndstoae and then dashing

PAGE 25

water on to t)x2 her\i;cO. reel-: to cause exfcliaticn, Hov/ev;:x-^ i.:; I'^r as i a:at avucc, no asiiGs have "been 0''iis rGT^or-lis pavticvio.vly ^.rteror; binf; sines it su^;,r:ost^; tuat ;^t a very ea.r].y il-:.^ ::\£U} h".a a ^op/visti rated kncv/leuBC not o:" 1 y ol 3 tone xraoruriKf/: prccosses but al^o of tne u:.9 01 fir-V:. For iiisnj JOc^v-y stone caohes coiis;! ;-;tin.j-.; oi a^-rov'hecidi spearheads^ croovod axeo. poln.?'hccl i.toriG hatchets, lartce lifc;;ryit^re and th'^r-o hey bc:ezi ;;:i;Clt ;jpsci.latioB, concorrii:)''; v/hy thesc:; yero deposited^ It: ko-jd^: porroct]y reaponable to 3\ipaost thyt s flint cacbo :•>; dcflcrioe-S I'ecentlp hj kit, 0th?;? supt%;-:?: vions thai; hav*^ been encc^Liritsr^d iri the litera^n^re are that th a'li:/ albereu in order to naho xinaj. ohJppi:;}r oasior, Viiile only a sffir-^l} iju:abo.c of tlo3cri>;;;iono i^iertcic.-;;, the pj^osenco of choino?!,, it ses/;'?: plc^iu-iblo to asourie that a f&raior plo;.rln^:; a fiel.d ^'/hr. uncover?^ as irany ss 3G^?eral hunr^^red flinc iiaplcr:cntft ar, one fell sv/oop is not f:oinp, to 3top to r;oti.co that the pit; also contains evidenco of fixv:;. Therefore, th^ xwusbor of ref^rrcnooa mi^bt be iCLUitipJied j^any tine;? if tlie ^•'cavaticv/ia ha
PAGE 26

14 Kontgoinery County, ITgv; YoxAh . « . a cache of 117 arrovrpointG on the farrti of , . . near a springo They lay about 6 5..oches "belov; the surface,, on a bed of ashes 5 inches thick, va.lcii rc;Sted on a hearth oi' fireplace, about JO feet square, of cobb].e.otones fro:,: the drift. The arrov/points averace about 3 inches i.n length and are of dnrk-blue and ?:ror: -^^lir^t, lesf-::^ha:^:;d (Vilscn 1897: '^71). Old fort and village site in G:0 Ane Ccuirnvj Missouri: Three feet farther frcni the centor was the edge of a pit 5 feet in dcptl'. and G fe?t in diaiueter. At one point on the bettor:. v:as a dIjc c-f Kiinuoe flint chip3 scaled off in r^;-hin^ iiaplei^'cntf) cf Linall size or delicate finish; there -cere enou^:-" of theae to fill a T)int cuni A f^jinhtlj ti'i'OAl^vr aocuivlty of ciwilar chips lay higher up (Fowk1910; 9^;)^ Dutchess County, I-Iev; Iforki iJhilj ei::ployod in di£:£:;inr, his npade broiight up a ruiuber of arro'v-poini';;, ho described t^::r: ro be nice],y piJcd s^'.de oy aide, ed;-eV'iee. in iv..e •. : '.c; rov.'C ^ There vrare perhaps two or three hvuue. -^d e. ; ";d , On each £;ide Hi-.'} on top vrere soiiiQ charred loes and ^;tj.chs, that eeencd to be the remainc of an old fire. They were iC or 15 inches oeJovi the surface of the pond. They are of a Lelue jiaspery flinty and see:; '.: oe in a?: imfi; aiched coxidition. l thought that pi.-ob./';.ly the Ineian;f h;:i brou^pu; them froiii a di stance (es I nave never founi any of the sane rock anywhere in thie neighberhcod; aud made this pocket and covered the trace^; of ":,hcio by buildinr: s fire, intending to retu^en ard finish thein at theiileisure: or, perhfeUo, they j.id then'' thej^e to prevent their capture by their env,e:ias (beepard 1877; ^07-3). In le-P-5 :r : Jb F. Snyder excavated Loiu::I "o, 1 of the Pecb^ei;.-; on the ;;-efjt siide of tr;o Illinois i.iver^ le.'.j '•• : P_:' e bclov' 3eard3u0v?n, are ee^oeite th.e :::outh of !;ef :> •• " . ' flllinoiyjAt t;u; bs:.e of the riound lee': ::.: c-e." of :. ; ay on -ivbich "v/ae a ua-s of black hornstone i;i'.;;leaeni;5,, ;;hat apparcntle bad i^eea tfirovn e o:er! in lota o:^ 6 to 20v vfith sand ovee end betv:een each lot, as thouph to iaolate then froic each other, '.ihis deeosit of 6,199 flints was covered v;it;h a t^tratun oT clay., ju :;a^bv;;3 in thickncea; and on thia a fire had been ...d for CO :. b , . V . . The flints for:ai-v: if' ^ naof te: -ef ^re vep/ . . . rueely fashiion^.'; M-, ^. . ^ — //'', r : p. "; f e. " . ]" \", . thi d.. ..u.x_ e... e.; .,.i;..e:.b. Ib.ee.e P:bJ..i e :.-'.'...: 112). It is latere atiar!; to notr^ thet i^^cat of tV-eee account' niertion chercoal and t};e unfir;ie''': -::.:'''.:.< b' the finds.

PAGE 27

15 This is exactly what one v/ould expect if thefie "caches" consisted Ox pre;Cor].is to be thermally altered priorto fiiiaJ. chipping. There v:ould be no reasDn v/hy tliey co-aldn't bo left for extended periodo unuil needed. Perhaps they v;erc never reoovored by their o\';nors because European :lni;ro duct ion of iron ana/or di.orviption of the aboriginal v/ay of life intervened . M^cussion In addition to the references cited there are other acco\;-n;:a tantalizingly iFui^gestive of therDal alteration of i-ocko used to make projactile points. It is toiaptinc to inherpret -chese descriptions as evidence of heat treating r,i;.:.i")ly \-ecr.:\uJ.?jts anyv/here in early clocu'n^ents the L>tex> by step proceduie involveci in therraaliy altering siliceous r^ateri-^ls ijiider conteoliod conditions « Several aut/iors , ;aost of vhoiC: have already been quoted, consistently rientioned the use of fii-e.. A sum::;iary of T:his inforiaation mi{;:;ht be as f olio va : These processes Cof shapinr;] are distineuished by such terms as breaJcing, flaking, ^ . . All are purely raeohanical; none are chor-ical , save a possible use of fire to induce chan£i;es in the reck in sci'ie parts of the quarry v/ork (HolTi:es JB^i^^; ?3') *

PAGE 28

16 It may be eoncJiicied, tuiopefore, tbat Crabtree Dade a signj.ficant and originu.1 contri^butj on ult':\ his obBcrvatioij, experimentabiorj , ajid description of t^iis phenoiaI first discovered the th.ci'ii;ii vr: ':. ' "Aen I was about 17. I v/ould find worked cib u.at'':.-i-:;l of superb quality, but v.'hen I iour.id t.. / ^ f.teriai. source it Vv'as never the sane end had :jj.<. e.!itij;el.7 different texture. I finally vjondered ii' thc;^ bad in some waj treated the stone and so tr.iedthe old coal range and heated the rocks vrbioh I buried in sand< After much trial and error, X v;as ahle to duplicets the texture of the v/orkcid pieces and decided" this was v/hat thez^ JJiust have done, I could ^et no one to accept the theory s hov;eYer, until the Lea Eyzies ccnj.erence -In 19S-!-. Tixier accepted it readi.ly as he Jiad encountered the BaT.e complex prcblem in Algeria (Crabtree 1969-, personal coKiriunication)^ Since 19&''i-j cany archaeologists throurliout tlie Hew sjxC Cld v/ori.ds are bec;n2">j\nc ""-o suspect that Duch of the stoue i-e-i;ia:''is ^recovered from archaeolo^^ical sites ]:ae been suhr^ecued to ther^iial treatment. Since the Literature I^eviev has revealed no accurate ca3?l;.deycri;;;t;ion relative to thj.s problen that iai[:ht be appj.led to arc}i3eolo£,iGH3. linde ^ ab least; a portion of the najor centv^ihutJ on airaed at in this investigation seeno to have failed, i.e., it should be possible to deinonstrate that prehistoric ot-opjos were cLvr^ro of th.e advantages conferred by ther;!:al],y altering their lithic materials, Honeveri enough accounts exist describing the use of fire in sone ph-.se of the :,;anuracture of fliv:;;: tcois tbar the evidence cennct he cc-nsidered entirely negative. Ix is not surprisin; that accurate accounts do not exist \-;n.cn it is taken iato ccnsiderati.on that:

PAGE 29

J. / 1.: liiuropeans who first encoiuiterod the American aborigines v;ere concerned v;ith itiatters othej.'' than stone technology. c»g, , survival in a nevv' ecological situation . 2„ It vas more fashionable to record esoteric cereHoriial T);-.r for inane OS tha)i the practical expects of nativfi life. 5. l"fon v;as ali^iost ii-xiaediately substit-ated for stone in r.iajcins implements; in fact even prehisoorically in the Southeastern United States, arrov/s mid spears wez^e often headed by materials other than stone: bird bones, bird bills, fish scalis, fish teeth, fish fins, animal bones, anircal teeth, horseshoe crab taxis, and oyster shells. Sone bad no separate head-"-the wood or cane of the arrov/ shaft was merely sharpened and served as the point » ^i-. Since chixn.;ins stone tools (except for c'-'-^ fliiTits) v/as not part of European technological luiov/ledga at the tiiue of contact ^ not enough ^vas kno-vn to observe or describe the procedure accurately, :nuch less interpret such an alien process, 5» Kost explorers, adventurers, etc«jV;ere ::?ot ^inong the Indians for extended periods. It is possible that this procedure occurred only at special tiiiios or in specific locatioi?.s and -./as considsered too nundane to inentio^i* To establish that desirable chan^.os go occur wlien silicftors :'aaterialft are subjected to critical te^'aperatxircs , it was necessary, therefore^ to turn to noniUjthrcpo] oQiical literature* Those publications v:ill be cited j.u appropriate places in the section on Kethodoloo:;y' =

PAGE 30

The ter'!!£s ilJlS^ ^-"^ i!4ilL'^ have 'been used interchfuigeably 3.rA i'c is dJificvAt tc de'GCPJ-iine fron x-he litfrature if Cxny actual strucoural ciffc ^encos exist betwe£i= tbe^i'. Fliiit is a tei'iii v/idoly used boi;h as a 'synonyii for cnert ejicir f or a subvariety of that materials Tarr says that flint is identical v;ith chert in textiiro mid coiir;osi~ tion and the term, therefore, should be dropped or re™ served for artifacts (l'etti;iob.n 19-49' 320). Thut:^, in describing chipped sttjne rooln, one iaip:ht say^ for exuiiiplCj that flint arciiacts v/eie j;:ani.ifcctured of ^rkeosaft novacuiites Pennsylvania jaeper, etc. This is, of co-^rse. already beinr;; done to a certein extent ana to those into:-.,'cytec in lithic technoiocy infcruation of tbj s nal.ure is important since it contributes ?;reatly to -n unaeretandin£; of the kind of worhinanshio tha^; raip^ht be expected or vr/iether trade rej at:^ o:!;eI';ipe ox^^iued :,.•' the 7uaLcrial is not local. lioet aichaeolosistG v^ould doilno flintea e rock co:!i'voecd cf ;cicrocrystalline guartz that breav.s v;: oh o conchDia.al fracture. fhAe In an adequete ronerai description, bat does not suifice \;h<:::n specific materials f.eon clivet'ci^e f^eo£;raphic areas are beinc; considered^ Fvo^v, the standpoint cf this investigation, knowledge of the fcrDiatlor nnd. composition of siliceous I'laterials native to the sbate of Florida is necessa-^y sixice el tore tion by heat •i;ir;ht not teke ])lace at the sa;ne tenpej:et'..n"r; j.n :uaterials v/t.ose structure is slichtly different 13

PAGE 31

19 Chert, beinf: rroci^. varies groatly In ito pb;yslcal c}iarctcterir?tlcs even thour^l;. the basic coiapoxiciits , the i:i?roxbe cr.yntals o.f quartz, are vniior-^i in character. The factors th-;t deterijine the physir;^! pi'operties of cherts are: (1) the £.1:^9 of the quart-.^ nry::t-ls; (2; hc/w the anhedr;;! crystels fit together afiectlns porosity a:icl fracture; (o) tlio ^.movnt of foreign Material present, lOBsil replacecents., arif?. other heterogeneities including; flu:-: corjpour-.'s; ('!•) void spaces; and (5) crystalline fabric (the crystals aro not eouidinensional or always randomly orieijted). Thus, in the Florida cherts ^ there are different tyi>cs and eveyi a. sii'vle nodule is not rjecossarily hoTno^eneous throurhoct its laass , The lithic rav? naterials used almost o:xcli;sivoly in this study v/erc Florida cherts. Justif icatioiTs f or usin;; a t;;erai^al term such as chert are as folDows, To this a\(th-.yr, at "leastthe terra flin^ indicates an ey:trenoly f:^ jj-e-grainsd ij-rceciel fcu/id in the chalks of J^nrland, Also, as stated fibcvOj flint is rscd as a coricon desigc'^tcr lor c.rtifactr with no speeific material intended, Usin^ the inoclifier Kiovvuia preceding;: the vrord chert calls to raind a particvlar type of nateriai mvicn as Arkansas novaculito, Pennsylvar/ia josper, or En^^lish flint does* O?houv;h there is a rar.r;e of differinj textures ai:d hoiiogeneities, 51orida cherts wei-e alJ fornied under similar conditions and share coinmon characteristics '..-hich distinsTUish then: from other siliceous rocks. There are a nuiaber of conditicns \mder ivhica chert vnJl for:::.. Florida cherts occur as a secondary fornistion due

PAGE 32

20 to the replacenent of carbonates vii.th Gilica?., Al]. of the c]>ert deposits in Florida sic? in rej.ationship to relict clay hills in contact \vitn liiuestorii:^ ; these generally corjrespond to the Ocala irch v;here eillcaous dopositc lie uncoriforii!™ a"i:ly over the Ccala Lis^estonj, Cherts also occur at the edf,e of the arch v;hnre lii-ie?:tones are interbedded \-/i1;h siliceous deposit-:, 'i'he ccoarrt^nce of cherts is thus in the upper part of the i,ocene Ccala Lin-ostone, and the 01i[;ocone a;ud Lc\/er I^iocene Format ioiis borderii}^^ the areas of the Ocala Uplift, Cherts found on the Ocsla Arch have replaced jiraostoneo that are Eocene in a^^e and those such as occur in IIo?:>nando and Hij.i shore Gountien have replaced liiieytoaec rliat are Oli.vocene and Lover liiocene in a-^c» Cherl'^ in the Ijiocciie dccocits are found as far soath as Zulpho Springs, Harc^eo County. There are ao cherts rr;turally outcroppiug alon;-: tlje east coast of ricriea or irx south Florida (Brooirs<, personal co/niiunication). Figure 1 shows the extent of the aroal dTstrihution of icr^nations that liiight contain chert in peninsular Florida.

PAGE 33

21 I I MIOCENE 1 I LI G OC E N E EOCENE .J^"^^ Figure 1. — Areal Distribution of Outcrops Probablv ^SSc^^S^^^ ^^^^* ^^ Peninsular Florida (Adapted from Cook 1^45, Plate 1; Brooks, unpublished geologic map of Florida),

PAGE 34

rJETHODOLCC: 0;hG experimejibs desc3:^ibed in tbip section \\-3y:c coii.cluctd prinarily to c;oter^:ine whether ivor;^ sort; of aiteratic takes (J.ece in nicrocryst-113i:o rock typea upon heatir^g thai: nakes the:u easier to f lai:e , especially to pressure flake. If such a cbange does o<.c\ho'^:e ^o 50" e] cv: I re;^n texaocrature urril the tcGt:'.nj: to.':.;':\. .vrr.r.e w-,:. jxicnt for a fr2>* Rapid rise ir t boated v;ere 3'-'',' tc'cperature until t •.:oh succecnrp Tncre. ; •usually 2hourn, : the materials "being

PAGE 35

All of the exT.ierinentc jnvolveu tlie use of heated and uTilioawCd spGcineiis but it v/gs necessary to cr-j-;^.tc a special catv-'gory dascribing the v-anj aiid varisd conditions vmdcr vhich the rod-: materials viero theriiially treated. 'Ihese tents fclDo'vod \-:hat might bo coiisicered an evolut j.on'xry seqnance since the rcjsul gs o£ one oxperiiient oi'Cen dictaioc; t?iG need for Biiother Vihich in turn sug£;ested still otho^ry. As pointed out in the Literature Reviei'j only Orabtreo and Butlers (196^^) arti^^le discusses iicatin^ of Gilicoous jnaterials frc^n an archaeolofricall;; si^^uificant poijit oi viev'j theroforo, these eDqperijJients are of a pionecx: Tv/a].va l--inch cubes, each weirhing approxiiuatel:/ ^i-2 grains 5 -.vcre laboriouyly prepared to be used for ccliproGxdve strerr:;th tects. (See headin^;^ entitled Sti'errth jletit^:: for ';be deecriptian a?id results of this cxperinort. ,} 3i>; of thOBo 3an]:l(:n \-,^yr treated as followGc Tv^o l--inch cube? ea::h of cbsidtani s-'.licified v . ' , uid 0(;ala chert v/ore v'oi-jhod prior to aabjecting then, to heat. Tliey wore placed in a Blue i: lab-Heat I-hixfio Furnace, heated to lCd"^-G for '\3 heura 5 ro;::.C!vad^ placed in a desiccator, a2id vroii:hed afoer they v/ere thoroughly cooled. They were then raheateo to lOO^'G and loft an additional ^1-8 hours to deteriaino if hi the moisture that v:ould be driven off at 100°C had ozcn . . ' ' h '"'" ' -hour period. It }\ad been .^... .. .J-: ' , :'0 change in v/eight. Thia ua.^v

PAGE 36

2'':procedure was follov/ccl for 150°C, 200^*0, and so on through ^^OCG 'out it was not felt necessary to subject the spaciKens to t-uci! long periods of hoar, cr to rohoat them at ei-.oh succoedlnp; ier.perature ;:ince no additiciial sigriificarrb -weight 3.or:s occurred with prolonged heu':in£: or subsequent aeatinc;, at the sa.me teKiperature. (The vGiiditj oJ this procedure ij, cotablished v-hen the next e-jcperdment is der^cribi^d, ) The recultB of vhls e:;rpepiuent are given in Tal:-le I,, Twenty-six specimens consistin^^ of oiurvplea from i^schert nodujes obtained froj'j various area^j^ of Fiorioa plus one specirion of Engli;::h flint v;ere v/enjjhed, heated, reweipihed^ reheated,, ana rev/eighed again through «ueceyelve teuiperatures to yOC/'O in the fcllov;inj^ v;ay. Alter the initial v^eighing, the samples v;ero heated at 1C0''C for '7A hou: after vrhich they ;-;ere relieved fro::i the o-jqzx vriile ]:iot, placed iriaediately in a desjccetor, end rev;oi;;ihed vrhen thorou.ehly eooj. <, They v;ore returned, to the oven and sC''i-i''3 heated to i,r;0'''; for an additional 'hcure and subjected to the aarie e: e . ; ./.-.re as deacrihed above. This process ^/as repeated until pCCC was reached, j;he over vi^e uvaen to the testing teiaperature at DO^C increiaents^ left at e'.;ch inorenent for 1 ho\ir, and then, nioved up,. In other v.erdsj it cook an additional hour to reach eacb cucceedinf;:: tei-'perature. The only variation v/hich occu.ered v/ithin the cxTeriment v^as tnat it aas not conaidered Jiecesaary tosub,ject tbe material to a total of r^a hours at each temperature as had been done at lOO^O. The fact that no airaiificant additional vei'^ht

PAGE 37

i li li 1 ! 1 i| i 1 1! 1 I i 1 1 1 i li j ! ii li

PAGE 38

26 the reduction in heating tiT/)e, It Ghould "be poinbed oxxt that luost cf the p.aTi'-.les tested did not exceed r:0 grans. Had they been lar^repj longer heating periods iiiight have been nece^jaary. One sa'^plo, however, v^eighed 9!^ gransand the percentage weight loss for thia sample vas coup"3:abIe to thot of smaller sample.:: of the sane material,. See Table 2 and ]7ignre 2 for t}ie results ol this e"perj..r-ent . Iigii.ro 3 graphically illustrates t^ypical weight tors patterns lor 11 or id a cherts, A nu]:ibor of samples vhich had been used far the expe3?irLiont described abov'e together vjith their unheated controls wore placed in ncist r^ure quarts sand and left for ori.e month, V/ater v;as added to the sand periodically to ';'>dutain daiirniess. Heated and unheatec! sanples of the sa:-;e •Material v;ere kept as controls at room te:uperature, the purpose of this exp.eriiuent v^as to determine hovj much laoistui'S the already heated materials vrould absorb as compared to unboiited ssjapies subjected to t/ie same coriditiors* The air.cnat of luoisture t^Uvon. up by the heated samples v;as greater than that of the unheated.. The heatec and iAnheated controls le fr at rooi2 teriperature during the :-.ovi.^i: yielded sojce interesting InforiiiaGicn. The controls j that had '}Arc.(x;y beeri. sub,iected i;o heal, lost less weight t^iaJi those ivliich had not, been heated, See Q'able 5 for the rosajva of this expertEient. 'One soaked saiaples were then subjected to heat to deterniino if there '.';as any significant difference in the ar-ount of weight loss betv;een the neated and x:inheated saii'ples i;-^ \r. t'-.r> '^iTiv,/. vn-; ;iv-.9 -.,T <..-^/. n}\ )-':;. ^.:c^;: c-^yiTrv-q occurrod. See

PAGE 39

2-7 HEATING EXPii:itIK.i:;N!r-2}0.D.;^2£t^r:il, -; yElGlii: LO:: Oi' SAliPLS;; o

PAGE 40

28 5 lo c: -! p -o o > 0) jO o o a to 4^ •: P 4? U 4..) too ^-! q j,q:;l

PAGE 41

29 p.A \ ! -| , yd) J' v;(-J . 1 — Ghort front York's prcport;y, ''']" \ Alachu? Qoviity., Plcrida \ 5 5 .la 100 l^G 200 ;'50 3( :y\

PAGE 42

f-1 r--.

PAGE 43

51 Table ^:for the results Ox this cjzperlnon'.: . It vi&c hoped x-hcifc this c-xperiiiient , though Ginvple, j.ai{^^ht prove to oe a rcli-iihile and inexpetjoive method to be onployed by archasologiata to d£;torni7ie if chipj^^ed Gtone icej'iiainB had been thernally altorec'. This v;ill be di3cussed I'urthex' under the hcadin^:; Archoeoloii^ical Application, but althoun^h tnore ir; a fairly consistent diirererce in v;eirht lost on an intrasaiuple level, oii an i2itersc;:iple level there is overlap. therefore, even i;C an investigator Icncv/ a {?;roat deal about the rock l^e wa& recovering (th;3t is, source, coMpcGition, f^tc), ho vK)ulc] have to be careTul in acsif-niny; too i^uch iT-iportance to v;eiGht Iosb. Ihis experiment aloo indicates chat the -weirht less at lOCC is T>robably not toe indicative since it would i'luctuace greatly depending on hov; dCiUp conditions v;ore prior to heating:. It has been deacnstrated that ail apprecicible ch^mj-je in v^'ei^^ht occur-s i.C th.o ssTiiples are left at room terperature after beia^^ reiiiovod freii a iaoi!n enviro/i-.:ent (see Table 3). Katerials xx-o:,: ihe field wnich i-;ere thought to have been thernaliy altered since t:;e^ v;ere quite luistrouG and nony exhibited a pin>:i&h cast v/cre reaped in order to coj.:-pare i^eight losses v:ith other specimens that -v/ere knov/n not to have been previoaaly heoted. The resr-?ltG arc given in •rabio !>.. if this table is conpared with Table P, it is a].u:-arent tfiot there is no si,7;nif leant difference in the aii-ount of iisoisture given off betv.-een the materials that bad been suspected of beinp; previously heoted and those vdaich \:ere bein^ heated for the first tinio. The results of this

PAGE 44

52 a;ABLh; AHEATING EXPEHIKEITT COKSUGTED '20 DZTERj^O^ DIVFERSIsCVDS ll^ HEATED MID UNHEATED SPEC11;EN3 i^.FTES SOAKING FOR OITS KCHTK y-t; Loss after 2^1hr imr;le at 3„0u"C Ah. A.h As

PAGE 45

TABLG ':y HEATING ^xr^rilTJENT GCNDUCTED TO l^ETEItia/iS VliKrHO? LOBS C] AilCIlAEOLOGIGAL SPEGIKjiNo SlioI'ECTZD OF KiWIlIG BBSII THE-RflALLIALT.SRSD Sasi^^le -! I 1 ,'eir^h.t Loos Afror 2'!]ir at 100 ^'C .19 .28 ,.2? ...OS p

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3^1corap arisen plus the data dera.ve-::? from soaking samples I'or a month in a laoiKo sand bath indicatp that it xn viot possible ro use weight f^aiii or loss as a pelishlo critoricn in clctormining ii' archaeoj o^ical specir:ons had been nub.jectad to lieate Soc rep i j' at i on^ _ and Jvxp3. o s i on It v;as no r.rystery to px-'initive man that firo could be destructiva to rock (:?Ge Lioerature Heviev;)^ but this investigation has att:aupted to demonstrate that •.frifysi siliceous rock naterials are cautiously si:b;iectod to heat^ an alteration occurs vvhich confemed sn afiviintar^a to prohistoric nan in the manufacture oi' his chippoc stojie i.^pleraonts, I'Inn had Kany thousands of yeans to discover this fact a7;d tcperfect the techniqua. f::.inca tho ase of fini: ax^.:} Ihe use of s'uone v;ore two of •cho earliest and most ijTiport'.uit J tens in the invantony of a physically and cultiirally e^/olviny; cnaature, it should coiae as iJO surprise th..t ho r.af:dually acquired an intimata knov;lodas of inieir att;;ibu"i as. The obsenyations to be aiso';ssed belov; ana probaV-ly ria.cb. like those a;vidr Ion;/ ago, Tho ;;iatoi-ials iriYclvcu in those oxpan5ij.ants v/ere all Floi-j.da criai'ts, I-hracticns i:uf;lLt occur ot di ft 'n-o^r.: tonpanauUi'GS^ o:: not at oll^ if otia^r aock typos Vvono used. Sufficiont saiapioc of non-llLoi^ida rnpitoniaj.s \-!ore not available lor orcporinentation. Those should bo tasted cvontiial ly becanao obo results v:oi\ld cor;;ainlY bo -a-O iplitenin;;-:. y.^n._^ny^2-=' C!970) 1' -: M bn : roast on calcine

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55 (salt-D, niiieralG,, etc.) \mtil a cveoklioa; sound is cai!.-=gd or imtil this sound .stop.?; to craclclc v/}aen exposed to heat.' Exx^losion occurs v;b.en the si;reys than is causin;^ decrepit^:.tion exceeds the ela^itic limits of th^ inrterialc When thi.B ntudj v;as initiabod, several large chext flakos were preT;ared in order to test their reaction v;]ieii. heated. The author' had jntendc-d to raise the tcraperature slovvly according to Grabtree's (personal cojiiEiunication) instructions but the oven v;aG progressinp; in degrees centitiirade while the author, uniLortiaiately, v/as thinking in degrees fahrenhcit. The o'ren consoquontly heated nore rapidly thar anticipated. At 'VOC^G the rocks exploded. The resulbii are shov;n -hi Fi^^ure 'r^ Subsequent experlKontc, conducted to deteri'iine the reasons forthe rock failure-, resulted ir one of the ma^or oontributicnc of this study. lif^ure •% ill'uscrates quite clearly several facb-i that refute oc^ections v;hica inay be i-aiscd v^-ith. regard to the iiitontio/L.al jfteatir;;; and subsocuent flaking of lithic if:iater?.ala . rhe picture shov/s potlid Iracturinp and blockjj enpular fi-^'ces ;^ith no bulbs of percussion , Tbis kind cf debris doa'> ;.ot occur b^^ intortional flakjno;. It differs narkodly fro-n t}iO thin;r^ing flakes found on archaocloj^icBl sites that are suspected of Oeinf? thei':::alJ.;y ali;ered.c It reasnblos e-actlj \vhat one v:ou]d e./rr'ect to resrjt from too rapid expansion and contractJ.on as rai.^ht occur jn a forest fire or if a rock had been placed in or near a hearth. S\3bsequent testinrr of Florida vjherts has revealed that:

PAGE 48

36

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No spa]li3is occurred (exoe;;\; en xaro ^^^^^y^^ ^ wbe:u b.-e !:;euroeratureB I'jeT-e raSsaa very ;r.LOw„.or . Fo -xp'i ^>5?ion occurred e"on ^hen the t2a;)ora.-curt; was^ raised rapidly to 550^0, alIov/?A tr> r?r;./in at 5!i>0°G .for 24 hours, and then moved 'co 'l-^'O v/. p--'o3ior .onc"-rod on sll occasioKS st 400^'C when -he"^iii8t3rial was taken to ^i-00°G v;:ithc-:b aliov^rais tiie teKDer^ituro to "be raised slowly or at^..^^.st leaviii^-it at 550*^0 for an exbended per.oa. -....a.ior 3peci;T.£ns did not explode as read:ia.y* TV t>(H tesi^eratux-e was raised rapidly. ercplo-xoH; or at least some spallin^, occurred wnen^^-^^J' "^^^-^ . r^aterial wes removed from tiie ovei^ aic -h^o o .v.:. or....^^ allcv7ing It to cool first. If th'^ taiaperature vas raised rapidly ^ explosion, or ^X least some Bpalling, occurred occasn.onG.,.ay but not orten when the jnaterxal v;a;?_ ri^iriov^K,. iro., ^ the oven at 330*G without aii.o\vjr:[;:; j.g x;o cooj. j.i.a-^o> Explosion -iid not occur at 3CC^G eve material vas remove froin the JOCG oven it;unftuxy>-.e Interestivisly, explosiorarej.y occur re... a. ..ay^ teiGperature when ti:.e material wa:^ ;ve^_oveu ^..i^^ir.-.-.atolv frois the oven if the tempora^^ure ^r.'i-^ oeea raised slowly and laaintaineo at nrie tost^riC reaper.:ture for a saataioed period » SxrloeiOii Jiever occurred when the material was tested a secoy^d time at the same temperaturo. '•-T-i.'--T^ f-'^e tfi-VDerature v;a3 raised rapidly a crac.v{:lir;3 So^se (decrepitatiorO v^'^s often heard at OV'0'0 and alv-ays he=2:rd at 400^0 when the materi^al waa reUiOVed fvon the ^^ren without allowlTip It to first cooj.. Ir waG not teard at. ^CC^'C r^'^:' :^y aaard w-^^t vTiaterials were heated 'or i 're. 'ihe^ saao3.es were placed dixecoly inio e p^^eheated oven at ^^O^-C no reaction, occurred a:" to.;: 1/2 nour but an ekceot a sample of Ooala chert; sr^^ppea^lrf half when, reis.oved froBthe hot oven and expcsou to air teispe mature. vni-^' <:v''^as were placed directly into a preheated ovori at; ^-OO^Cj e^'plosion corciaonced after approxinatel V 20 ninutey. The oven was turned ofi imiaedxptelv'^ e^oloaior ccutinusd interjiiittcrK:ly^ nntrl _ the overi booied to about 575*0. Ail^ aaffipies haci ^-..1, ^ ^ • . :. OVC ?ith the except: t vjhich die: dci: .

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58 Two samples thot iiacl ooeii licabed to 350*^0 for ?^lhoars were re-aoved from the ovon v/itb. ton^s v:b.ile hot (Gtill J^COi the tori^-G were v/arned on the side of the ever:, bafore touchi/;.^; too hot s;:cne.. One of these aaiaples Empped in half vn.th a very lo\;d bound (room tciripei-ature v;as about 7i5°G). Cold v;ater (tap V7ater) W3S dripped alon~ the ed^e of the ssiiplca v;ith a dentol Byringo to soe if they v/ouid flake — thoy did nob! (Sec Literature :teviev; for accomits describinr;; this alieoed phcno]:aenon . ) Tiie Ga::npj.os v-ere thes placed directly under the tap and cold v;ater allowed to flo--r over the entire Baiaple* Thl^. resulted in en audible hissing sound and a cra::;inr: of the Dateriai, The raiae procedure was xollov;ed vdth two samples that had been left at ACCC for en additional; & hours. Gra;^ing occurred and Gubsecrent attexpts to flake the Eieterial caused it to crumble. It v/as impcGSJible to pressure flehe this Taatev'ial becoiiee the flakes could not be renoved in a prec:icT;ebie way. ~hc specir^icn. literall;/ fell ?part (see ?e^]u:'e en queiv;:' .. f: -.: d;y irroguj.ar cr^cka ether e>:perinents v/ere conducted to test; the s:Ianifican.ce cf the crackling; sonnd vrhich occurred vrhen speck'' v: -:: , na::oved iininediately froa a hot oven. These expexf...-n-..:. ..il?. be discussed at the end of this section and in those deelirr.; vri.th Pctro;;:;raphic Aualys:is and Strength Tests.

PAGE 51

39 bOd

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^10 Vitr eougnes3 To vitrify is i;o convorl;; into, or c^o.se to reserfDle, glass or a glassy substeiiC? by hect and fusiorj, Tlie r:ope vitreoue en object in^ the :r.ore it has the luster of broken plass. In. cr-dcr for a cryx:tocry3te;llino reck to bo converted ir;to an ei'norph.o'uy^ , noncrystallan? structxn-o^ it 1^! ^^eceysary to subject it to tenperatijreB of ea l^i-OO-l'/OO^'C (approxi.:-abely 50OO"?). Aborisinal peoples in th'^ staue cf Florida coiild not achieve or i;ie.intai:: teTsroeratures this hir^h. Tills fact is kno^vn by the quality cf the pottery re:ii3ins v;hich indicates that pottery v^as fireo at a much lo\vcr temperature— probably not over ^30*^0 (ca 1C'00''7), Eiace the practice of alterinj-, lithic materials see^r^s to have occurred on preceramic levels in Florida, it could not be assiiried that earlier inhabitants vere capable of producing te::iperature3 higher tnan their descendants. IBosidea^ from pctroj^raphic analyses, vhich v/ill be descrjbed later, ithas been demonstrated that the si^e of che cryptocr^stais does not chanp;e even thou-vh vitreous luster occurs afiev heatin^% FloT'ida cheri:s are characteristically nonlustrous and cou3:se graiued except for cJi area directly* uador the cortex vjhLeh li-ay be as thin as 1/6 iiich or as thick as several inches, this latter beinr^ exceptional c (•ocasionalJ-^', ho;;eve I ^ the chert is slab^ike auO iedav^ net exceeding an inc/i or tv/o in thickness. When chect like this is found, the fins r;reiued area ^-cnerelly exterids froK corte::. to

PAGE 53

cor-bex throughout the entire hhickneGS of the rock and ^s extreii-'.ely r^lr.r.s-lll:o ^.nr^ hor::or;c:voovsi, Tyv^ioallyj ho^-;ever, the chort is found in tliick roundod i:ioc1u.1-js or bods aii.a the fine f;raiucc! aroa urider the cortc" rapidly BhadeK into &. ocar£-er grained vvc-3. farther vvlthin the .insss., The reaaon for tbifi di i' r-{:rcnce in tc:vture is" uot olear but it occurs during repls.ciaont of the lii-.eocono by sij.ica cxi^d. laight be "duo to a c3esc:ceaKin£, rate of precipitation because of tha diminishirc; ret'i of supply of 5:oli!tiou as cousclidatioA procoeds" (Tol}^ arid Weaver 13^?.: :?00~'.j. The smaller tuc size cf the cryptocry3t::is . the more the materiel vu.ll exhibit t^io vitreous luster of gl ase ou a fractured surface, end by covirrest, the Isrrcr the cryptccrysttJ s 5 the less lustrore is the ag?;re?::;ate inewe In. appeareuce , Intereetiuf:ly, after coaree greined chortis are heated slowly to eround J^O'^C, left for a perioo of tine, and viubsequently frectured, the fractured eurfacc exh;'bits a -^lees-like lenter but the grain eize hao not been obenaed, The reasons fc;^ thie are quite einple aed vol!!, b? expleined irj the diecaaeicn V/hich foilovrs. fa?>le G f.v}:;".-::r-'.zes e>-perli;K?nts uei^'C lar:.,e and eriall ^'ample:: of chc:.-t;5 froin different rock jaaeees and locationa. These tet^ts were co3-:ductod to determine the len^bh of true neceasary to effect alteration which reaulte ir a vitreous fractured surface, Each group cf sa:np.i.e;f^ heated at each teniperature wac taker to IOC'^0 a:id 3eft for 2 hours after vfaich they v?ere raised by SO^'C increments for 1-hour period-

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42

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to either 350*C or 400'^G ac indicated, -aio. then left at the uloi:natc tCii^poratni-e for the: dr>Gisnatecl r'-ri-d of t:-ne. The over. v;as shut off and the sonrylGS allov;6d to cool in the cvy)... The gradual oxisot of vitrification oeous to [^o hand in ^'.^.rrA with an incrsacinr^ eaae in renovin:: flakes. If alto:L"at:j ons take ploee too rapidly^ dra;uatic, deBtructive events occur. It should bo e:'iyha?ised th.at vitrecusnets 15; not apparent unless tho rock speciiuen is broken or cliipped after heatin-.':. The exteiior B'arface of tl^e heated stone remains dull. This is illustrated in Fif^ure 6h, The inloxviation prooenceu to Lju.:ri point has been nainij ohser'i?"8tion ynd description. The data nov res-ain to be interpreted and the si^;nificanco of the expcriLients di^-cm-oodt It sec:r.£; fairly clear that no reliable inferencee con be u-jide froin. cjifforences in v/ei^ht Ices and gain to h'O.p in deter:-nnin£, if archaeol eg: cal T'oeciiAena have been tbcr';;a^'inr altered, iv/e}! rnder controlled conditions, tho'in): si^;nif leant differences vrere observed for the n?j5:e rock \^;hen liaicsii uere eithe:t" subjected to li&at or kept as controls, nothing; reliable was j^ecorded when rsokina coapnrisonG betveen oiffej^ent rocks even v/hen the Tnotlod of exposure vaa identica:. In addition^ tl^e aiiiount of v/ator driven off, vrhether v:xc^f:t or ar^all, Tnads no difference in the chan^.e vrhich i^lvinatcl;^' resell ted an lonf: ari the temperature effectdnc

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44 Figure 6. — Vitreousness Occurring when Florida Cherts Are Heated and Subsequently Flaked. Top: Specimens were Heated Slowly to 550*0, Left for 24 Hours, and Cooled in the Oven. Bottom: Specimen was Heated Slox^^ly to 500*0, Left for 5 Hours and Removed Immediately from the Hot Oven (note relict dull area that has not been flaked after heating).

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/I5 the cliange vr^.rreached and maintained until the chanQo occi:;cred. Obsidian (Table 1) lo5Jt no \:3±r.'ht at all but other test:3 -^uzij^^t tha"c; a ch-iii_^e ij.igho o-^cu': (sec Ru^ction on Stren^tih Tests). A q^artH crystal &nd piilveriaed quart z, lost vcrj' D.i-jtle v/oight (after 2'^ hours at 550^0 they h?.d 2ost ,01S;' and ^0-^;Cj, respectj.vel;/) , out it has been stated thnt quarts bacoines easier to ;:?lal:o (Crrcbtreej personal coM}:iun5.cal;ion; Kan 1333. 3^^)Siglisli flint lost en^y about .155?'? to * 25% and, becyuse it is fA.ne i^iainedj \^e si-spectad bhftt line f^naine^" Florida cher*;;y v;oxild lose littj.' wci^fit end coarse r;rai7aed PJorJ.da cheri;s wouj.d lose iLiore = 'do'.iover^ there does notseei: to be cjiy 3i^;niincant ^ prediotable difference betv:een tha ar-onrn; oi v.;eii^:bt lost ;;nd crystal Size in I'lorida cherts, rhis could be due to hetero{;;oneities srnce even fine 5;rained materials n-j have lar^:e void sauces that canriot easily be detected^ I' is i^ore liJvely because, even thouf^h there is less v;ater in •^-ny g;ivon interstitial space vheii. the crystals are si-all,, th.jv Bj.'o still snhedral and probably are not :iacked any better thaii larger ones; therefore, the saitis anoun;of v;at'?r exists even thoujih the ccyvtals \vhich it sueroiines differ in size^ 'Che differ '.eirrtt less for Eny^lish fliat coxepered to I'lcrida chert aight be due to the conditions Mrid.eT which tbej vere forined, ?!Lorida cherts .^• aluy contain i;;ore water vscuoles. The cr;yptocrystwls of English flint are probably more clcselj" packed* Tho siiialle the size of the crysta''s, iho propter the surface area unless the crystals .

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46 If o;oal v/ere present it rAight "be a simple natter to exT'lairi v;bat; occurs v.'hen v;ater is driven off t}iroug'>i heating: th^v opal v;i'.cn dried v;oyld crack ejid adhere incre £i.r\:ilj to tbs -uicrocrj'Gtaln exactly cs jeilo vculd -ce^id to stick bo tie side of a gloGs. This might resulb In a bi;idinp; of the LiicrocrjStalH , 'jjhe presenco of opal as interf;titi.al iric.tei-iol in. chei'tj howevo.:', has been quite thoroughly disiiiissed C'olk and U&aver 1952; Schvalz 19&0), Attevapt^ to detect the presence of opal in this study produced only negative Despite tha discouraging coiiiments thur> far^ the loss o.f •• ater ^diich occurs \;hori cherts c-xj'o heatsd i/t a -'-ery si:p;/j.fica.nt foctcr in the alT:err.tion of the rock. V'ith the roncval of the intercrystolline v/ater, the jTiicrocryytfils be-cc'i'o far.^ily ceinentec. fiius v;hon a fracture occurs it passes throa^rh i-ather than around the individual crystals. In ot}iei v/oi'ds, tho stone breaks noro like glass tho'i a rock fCBX-OPjate even thcuph the same nicrocr^stalline structure and T,extaro are still present* ThiSo in turn ^ explajns i'. '. : ' ' . :.' 1m vitreousness o£ the fractured surface,. Civcrl: is co'ipoSird of :::icrccrystals v;hioh constitv !>>.;: the laineral pliase kno:-;!! as chalcedony. Iiin-^::-:\].oyicaj.l y, Cj1?1cedony i.s \'a~ry or crreasy in lusher but indi-i:h:.a:L faces of this Uj^ioi'ul ore noririally not' seen because the cry.'tals are anhedral (no definite: shape or orient:^tion) , visi^ally subcquidiinensionalj and inioroscopic . Therefore , V/lon fractiu^e occ'irs, especially if ' .• . ^ ccarse p;rained; the

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^7 i"rcicturcd surface is dull due to refraction aiid poor reflection, /ifter heat:Jns> the fractured suriaco is vitreous duo to the greater traiicnit tance of 3 ight v:h.±ch occur;:when the fracture passes through successive cicrocrvstals and iritercrjstal spaces revealing the intragranular nature of oucrtz. If the laaterial is fine grained, it seeiss to alter sli;^htly faster ;^hich may be because* even thou,^h it coutai^ns the same overall amount of i/ater, there i^; lees raoietiire "being renoved frorr. exij given interstitial area, 'fhe:re seer.s to be no correlation hetv;een crystal size and tL.G teKperature at vjhich alteration occurs rn 'Fl.cridii. cherts. Trere does seea to be so^ae correlation betv/een tbe coriposition of the chert and the length of Gime as well as the te:iv;oraturo at v-bich alteration occurs, I'ho fact that Florida cherts are formed as linestone roplacei-'onts ^cas discussed in the section on Katerials, Some of the muterr.els tested appeared to leact differently than o-jhers in that t'ley did not resivond at the sai:-e tci^peratiir >s or time periods; also they did n;.)l cecrepitate or explooe* Except for the area directly U2:d':;r the cortex vrhich alvjoy-i ;-::.;::; 3 to be very siliceou;-;, a satisfactory chan^;e did not occur in ooi:;e rocks at the testing tai;:peratures v;bi.cn usually effected a change. Vhen temperatures are raised slovj-ly aiid left at; either J'jO'^0 or '^iOO'''C a change occurs vjhich is vovy apparent v.Jben the sariple is subsequently flaked revealing; a vitreous fractured surface. In addition, it is definitolv easier to Tnairifacture stone implements (see Pigure 6a.) . ' :;tater.;ont

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4S is not 'baoed entirely on intuit J on (s'jo aectiorj. on Strenstr. Tef:to}. It roiaains tc be explained, however, v/hy it is that il" the 'oe^aporaturG is rjisod too rapidly, explosion occl^tg, G?he crif-inal weight loss at lOC^C is due to the rericvnl oT cidf'or-bed v;ater held en thr: p^ui-f cces of ths individual Eiicrocoystols. After this initial 3 arge v;ator loss, the v:oi3ht i-enalns quito stable imtil ^'jO'^C. Yv5.or to t,his, the tenvperature j>robably ha^o not boon high enoo':';h to roixovo the cheiuically binntd v/ator hold i.n the intercrystalli''i; aro£f3, 1 £;uspecfc that the follov^ing happens: 35C^C is probo.b2.7 a GUfficiontly hi';^h te::nperature for alteration tc tolas placi. if this teiaperature is KustaAned far a lona period of tiiie (aae Table C-) , If the teKoeratuio is raised to 4C:= C prior to the gradual removal oT the cheirically bouj-^d -vatar, explosioy;; rooults because the alteration pi-oceeds too ra]^idly. Vitriiicacion is always evident, at least to sone extent, on the fractured surfaces which result fro:.': these explosions. i'liorcioi'e , some chanac ^i.ust oecur aliiost inujediateJ y wiion a a-i^j.bicril terperature is re;-ched even thcu^pi the material bloos up at the s^^iO time,. Ihore doee not seeii to be any I a.; 'ic'us studj' daal:ij-.c; vd Lh thi\; X'— ^"-l-^-adequately, ..::.Hlon ^"328) in his article on the rupture of ^lans discueeas the fact that {^lass vill fy^clwre v:]\oii alternataly aab^ected to bear, ^nd col^p al .J. aork Licatlj' dcocribos t'la type of fracture v/hich. wi.ll occur depending; on the sfcroos •o v)hlch the material is aubj::^: ord . Perhaps the ansv/er lies ;lu the fcllo:.-:in;state; =::it •

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49 e . . principles of surface chemistry , . . , V/hen a crvstal consiGts of hinlilv polarizablo anions of lar£,'e siae , togethei' witu sraali , highly charged cations ^ then the anions will ''oe puahed to the surface of the crystal and the cations v/ill be recessed. Thus in a Viiiorocrystal of '}u.:\rt2. oxygen ions predominate at the ourface, v/hile t,];e silicon ions are depressed. It is believed that each microcrystal of quartr. then has a negatively charp^ed "skin," and ef.iectivoiy repels ad,;jaoent randonly oriented microcrystals . . , fracture probably takes place betv/oen the polyhedral blocks because of the surface rei^ulsion forces (rolk and V/eaver 1952; 507-B). V:b.en the rocks are subjected to critical tenperat are a ^ there i;iay be a change 5.n the position of 02:yge;i and sjliowj. iont^ ac. descrd.bed above* If the ions becoice too excited v/hcn te?:-perav,ure is a.;:'plied rapidly, explosion i.^ay take place c This may also explain the cj.ickinf^ sounds vrhich occur and often result in exfoliation vihen the material is rapidly cooled. Perhaps the reason these clicking sounds aren't heard v/h.en the material is removed after a sustained period is because the process is coiaploted and no further olLccn^-o is tab in;;; plc'cc. x/ailure v.-as accompanied by jieculiar ''clicks,'' ihese "clicks" v;ere heard early in the coolinr period and never duriua the heating period, v/hen the rate of tenperaturs ch-anre v/as lov;er<, When the ciips v/ere heated*, to a sligntly hia;her terrperatu.re , no higher T^ercentage of failuiea v;as oL'served (Pressler vsid Shearer 1925: :507). Material that haa been heated to ^CO-0 is no easier to fiako than that left at r^SO'^C for prolonr^ed periods (see Fir-. 6b). A nuriber of Ganiples v/ore heated to 600-'C^ 'U:!:•;rl chippin. of tliese speciiaens did not reveal any furthci.;:. a ... either. ,, ;n te do not support this observation since t}iere is increased stroncth .loss ivith increased tei^peratures under po?'rt tensile VJO J

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50 load. In addition, Vv'liilo there is no apparent incre^.-se in ilaking sase, quite often atteiiipts oo c'ulv flint materials thcxt had hocn heated to 50O*^G--6OCG or had been heated to ^30'C"/i-00"C and removed imraediatel^^ Trcn the hot oven, rr~ sidicd in a lateral snay due to end shoclu This fracture did not occur at the point of impact, The fractured eurfaco often X'osenbles that illustrated in Pigure 8c 'i^'lintknappers are familiar v;ith this type of failure since it occurs v;hen a siibstantial bio;; is inpartcd to a roch \vhc3e ma'-is is not adc'^iviete] y supported to absojinj tlie shoe^. With theae heated raatorials, hovrever, failure occurred when only f0.ic~ht pressure or percussion v;as applied^, Tiie cor'positicn of the chemically bound water mey not be identical to water as \:o normally tnink of it^ Inat :i ? 'il,jO. If the hjd.T'Ozon a?id ox^j'-gen ions are disacc fated end the oxygen plus paru of the hydrogen are pivej? off Then a certain i-e^apereture is reached, the reinainin£; hydro£'i:n i?v. \:i?n ite positive charge may hook up v;ith the negatively ch, 'r-yyen "skin'of the Liicrocrjstal and serve as the hinder,Or if the dep;.^e3Sod silicon ion is af^itatcd, it ; :':'^~' ,-'• ^. ion froan adjoining nicrocryntal IjO/K .r ii^?e XOVi cancerninr^ the reactions of var-icve types of fiinta v;hen r'..'.:-:!^ Their ai'ticie is coi^c ' , -/a ';;;r-ij y \rith flinte !o.-(,' Ir: the ce3''ariG industry but n".y iiold sorae applicable c i. rnce teiflperatures of I'iOO^ C-lyOO^C (>ZCOO''}P) are

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5>1 needed to transforra nicrocrvstallj.ne structurps t-o a noncry&tailine foiuj, the vitriiicatlon v/hieb occux-s v;heji j^lint materials are hoafcod to onlv jsC^'C rr-ust be; o.ccoimtsd .for in another vvay» The i,c:puritie3 in flintc [^enerGlly act as rj-uxes^ due to eutoctic developiaents, . . , . I. . r'OoOv v/as found ir: a.l?_ flints varying fros 0»0? to O.l^'^'per cent, vrnllc iron is objectionable as aii irapurity because of itr. discolcrinei e.tfects, the small percenta;;^e precent In the flints vroold probably be of no significance in a body cci.apo-.it ion,, Soiue of the American 'flints are free from Ca5, arid others contain generally less than the French flints. O^ho loss on ignition varies from 0.15 to 0.85 pS-'? ceut mid represents C0._, dissociated from CaCO-, , an.d" adsoz'bed or chemicaSly coubinod water (Trcisltr and Shearer 1926: 292-5}. If the irapitrities (or cornbln'itioijs of inpur:! ties) contained in Florida cherts ai-e serving as fluxes (s-'ab stances proraoting fusion) to fuse a thin surface film of th2 crypoocryskals, then change v/ill occur vhezi the n.eltin£point tei^Aperaturos for these impurities arc reached (euteotic dovolop::ieat)< If thjs is the caseansv;ors are fourd for tvio pu^.zlijip; problems: (1) why vitrification occurs at do iiot respond at the sawe teraporatures— -the i^Aoltin^: points 03the fluxes are probably dif<-erant„ If thpercentase of oalciUiU is quite hiph, this also explains v/liy certain niatorials do not :naho a desirable chansa despite the ter;._(. era tare or Icn^ith of the heatin;;;, parled. GalciUin will serve as a flux IT pj:-eaor,it i.u. sraall quantities, but presents the desired rcactior; frosi cocurrin;: if present in large qu3.:'!.a.i ties. Three ?loriaa cheats which resaonded

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dix fcrently vihen heated v:oi'e subnittea to the Soils He-^Jb-rtnient ai; the univc-i f^^itv of Florida for Acoiiiio Ahsorption Spec;trcphotoraet'";r analysis » The rc.r>vJts of thio analysis are given in Table ?» It is not hnovm //hot percentage of CBlciun is necessary to prever.t the desired reaction but it is interesting to note that Ocala ch.ert and High Springs chert had considerably higher psrcenteges of calcii'.a than the tvro Johason Lake specimens. The Ocala and High Springs cherts consiscently reacted differently thai': Johnson Lahe and other Florida materials tested in t;hat the expected change did not occui' V:ithin the same teii;pcrature and tine ranges. Figv.res 7^ 8, and 9 illustrate various ty7pes of frsctures. figure 7 shov/s an example of a pot3 id irocture ^nlj.ch occurred only when the inaterial s vere lieated tco rapidly. Figure 8 shcv-'s the type of fractured surface ^/hich often occurred i-;hen the samples -./ere renoved frcn a hot oven to a cool environ:.ient ^ The specinens in "I'igures 7 i :-d S }iave broken v.'it;'i a conehoidal fracture typic.-.l of flint naterials. Figuae 9 is a tbianing flahe^, intention-ad 1. y struah froD an obsj.di-r.-n core, xn add?ltioJi to the conchoidal fracture . this last specimen posr^esses a v;elldefined bulb of percnsaicn net present in Figures 7 ynd 8. Figure 9 ser-yea as a rc:id.nder that a iiLicrocystalliae rock v;ill break with a conchcidal fracture but no bulb of percussion v^rill be evident unless jnpact has tahen pl'ice. The results of the heating experiiaents establish quite clearly that crystal beuiidarics Day be a disturbing

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55

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54 Figure 7. — Example of a Potlid Fracture which Often Occurred when Florida Cherts Were Subjected too fiapidly to '4-00*0 Temperatures,

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55 Pigure 8. — Examples of a "Crenated" Fracture which Often Occurred when Specimens Were Removed Directly from a Hot Oven to a Cool Environment.

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56 Figure 9.— Specimen Depicting Intentional Fracture with Bulb of Percussion and Typical Fractured Surface Emphasizing that Impact Has Occurred.

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iji.n.ue'ice v/hen aotei.ipting t;o predict fracture. T/ioi-ef ore , th^ wore £.?.n£;:^;--like the me'^^erial^ the noro predictable the fi'acture. Heated cherts are inore ai^^i-^-li-'^^^ '^'^^^ t'actMres are not only xaore predlctatile but eaoier to execute* Iron Gontorit ol Florid-i Chert The incorporation into chert for;:i?; tion3 of coKcen-tratj ons oi" iron v;hich i.MpaiH a pink to red co] ov upon heatinp; is usually because of secondar-eni-ichinent; resxxlting fro!:' the nobi.lity of iron in iron-rich. palc-osoil3 or; bog deposits. Iri soine of the Lov/er Iliocone deposits, however » another situation exists in v.'hioh iron seens to have boerj inccj.'puj c.te I uL; "cL^ tiiiiS oi .-ilicificaticn v.hich resulted in -ohe chert forr-ation. In addition, althou^'^h they are rare, brij-;ht pinh colors (ca 5 2 7.Ai-) (r.m^sol]. I^A-^k' f-i^e Eo:':'etiTnes found xn cherts imbedded in terra rosso residual soils on Ocala Limestone. These cherts ere dull or eartli;; in appearance and do not resenble cherts ^^^hich have been thorn; a 1 3, y ii 1 1 e r e d ( hh K . 3r o ok s , v e r s c n a 1 c o,"r:iu-) i c a t i on ) . Color chanf~e tak.es place betv:een ^-rO^G end 260'^G in i'lorida cherts. Firure 2.C illustrates the variation w:"'ich results dopendinn; upon the aiiiount ef "jror present in t;!'e ssiiiplc. Unfortunately, X;^.C: color representauion wos not atcained but a.;:! analysis of the iron content (sec saiiples in i'ipure 10b) revealea thaS: sam,.aeB cha:i;-,inE^ froin 10 Yu G-V^ (between ^rcwj pale orange and pale yollowish bro-n but nearer the latter) to 10 R V^ (between pale reddish crovn-i and dark rcdaish bro^-;n') coDtoined 4C00 nom

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58 Figure 10. — Heated Specimens and Unheated Controls Illustrating Degree of Color Change Depending upon the Amount of Iron Present in the Chert.

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(c''!r;:o) of iron. '^bo;-e c'^mcing fr-ojii IT 6.5 (bet 'ooni \±i-^:.':. t^rny and. laodiujii light gray) to 5 R 7/? (betv;een ;-;.; ; _-' pii:k aud p^-Io re^l) o-ontained I'-ycX^ pjM' (^P^'J/* TV'-;.;-j ex~ ii:! biting ;io cclcr chcfn?'^ Cwntainod ll'^'O p]^::: (.1!!>0, It shovld bo -nphaslzsd that: 1. Color chongG occurs onl^ becaii^o of tjie o^iidation ox iron and vill not occur l.f no iror; is present. Kaif^'/afe-aples of Florida Eaterif-ls &jA nov c}laJ^go color t 2. echo teaperaturO; 'at •/•hich color chc-ngc cocu3:'s (240*'C"2oG"'G) is not 3^'nchroJf^ous v/ith t>r> change tc vi-crs^ovs luster in j:'lorida niateria!! y-ca 350''C~40C''G for si^stuined pemods. 3r Therefor^) ; -riolo.?,' chahg/xcannot be used a-a reJ iablv crito:rios; (at ijoast lor Flcv^ida elierts) ir • :-.^-,r-taining if materials rocovored froiri arc' . ' ' ' ;a.") sites have been intentionally therraallv :. . L,.,j.-:;,.,.. But if a combination of vitreousness aiid color ciiange occur frequently on artifacts o.r v,-asf:e flakes as is the case i7i Florida, the a~tuiiption t-i:;at-.;acS3:r;V?ae 5ul:,;^octing the ehpivt '^.o t'-.i^rjeraturofv stiff ici^ntly high to caus,e a change prior tc final chipping is Vdlid. Strength T^st^' Unifbrri-KiE;od saxplos ;;er6 prcporad in order to clotcrnino J by standard rock riocl^^^ifes, tJests , v^hether any differences in c^:jrcpreG iivc and point trn«ile strength exi:jt X^nitially, t-^^^lve l-iyich cui)^s V'^--^:'--"-:-jred, each i/eighing approxi:=:ately '^7. grams. Usinr : mQ blade, it -..0. ? ..o^:;3St:.ry to saw thy stone as accurat^^ily as; possible to the dsisirsd diriiensions and thcii laboriously grind -the sai/iplejs.'^i.to e:x;actlv one inch, Aiiv d<>viatijn v^ald hc-a rendero'^

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60 time consuirj.ri';, e. corinj^ device v/a.s used which r;;reatly reduced tho time needed to prepare samples. Usinga drill press o,s a basic piece of iiachiijery (Firure lln)? Corc-L;::--tic diaiP-ond core bit having an inside diajueter oi" 1 incih ± .CG5 i"ith a 6-inca core barrel a^nd 5/S-inch dianond penetratioii v;as constructed by ."Jiton 3r;it and Co., Inc » , Kew Yorl:... This is a variation o:l a Gorernatic drill used, to cut holes in glass. The Ciiert nodule to be cored v:as clanped into position as illustrated in 3?:*_g'ire lib. The d^ieiaeter of these cored ssFiplcs v/as exactly caa inch. The cored saipples that '/"ere to be used for conpressive tests v;ere then sav/ed as close to one inc): in lon^:th as possib].e and groiuad to precisely oiio nnoh. This reduced the nuj.iber of surfaces to be grouj:d fron six for the cubed samples to tv;o for the cored saiaples., The cored sanples thi.t vicrc to be used for point tensile strenf^th needed no additional preparation. Of the ojriginal tv.-elve ].-incb cv':'Ci<^^ six v/ere heated to 'iCO*^0 as described jn the sootion on Heating i;::perimen. ts and. six vrere 3-:cpt as unheaood, controls. One sample each of heated, and utdisated obsidian, silioi'ied coral, and chert fro;;i a quarry J ''li^os north of Ccala' v/ere i;.sed for conipressive tests, Goiapressive s-Grerv;th data c^btained frcn the cubed sa-mples of Ocala client v/ere unreliable due to error in testing; these were discarded. blabsequent^y , tv;o cored To identify this material as to location it v/ill hereafter be called" Ocala chert.

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61 Figure 11, — Composite Illustration of: (a) Drill Press, b) Corematic Diamond Core Bit, and (c) a Chert Nodule with ores Removed to be Used for Strength Tests.

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62 samples of Ccala clieri;, 1 inch in .lonj^th, ivere prepare:!. One Ox"" those v;as heated to 4G0''G and the other was kept ec fill unheo.tec). control. Both ci\bod and cored haatod sanplcs h-o-d been rericvcd froia the oven irnnediatel;at the end of the heating period \-;ithout first being allovjed to cool. The si^^nificance of this procedure v;ill beco.re :rr;--,-^r3rt later. Arran-j;effients were mace v/ith the CiviD. Er^ prince ring liepartnent at the University of riorida to test the Gtr^ngt of these :caterial5. .Dhe equipnient used v;a£ a ^'OCsOfO-lb capacity Riehle Universal te3;;ing raaohine v/ith hydraulj.c type lo^din^ and five ranj^es. The results are riv^n in Table 8. fhe cross sectional area of the cored sawplot; v/ai^ -s'car.dardized to 1 inch ns follov/s: A .735 The finuros resulting fron the coupressive strength tests for blie cored saniples v;ere then divided hj .?S5 thus e::^Niressin;;;; the force in pounds of pressure -£>Q'i: square inch, In another test^ cored sajuples of cesidian and High iSprinas cbert v:erc orepaxel foj' ccTi:prossi''e strength t?sts as described above. Cue sar^ple of each of these reaterials ^'Tos heated to '4-C0''C end alloired to cool in the oven. One sample of Oc^ch v/aa retained as vJ^i unheated control. fhe resiilt;^; are p;iven in Table 9' ^©^ Ticure 12 v/hich f^raph lordly '11] ustrates the data presented in Tables 5 and v. 'be coiRpressive tests yielded the folloaJ.nfj i-esults

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TAia.3 8 RESULTS OF COIIPRESSIVE STIOIGT^I Q^ESTcv V/iIEN HEATJ^D SPi^CII-iEKS ARE SUBJ:2CTED TO A COOL Ein/'li^OKriSlIT V/liILE STILL liUT Saruple

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64 o

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65 siliceous jpaterials arc boated to tomjieratureo of ^A-Q-O^C5C0'''C for sustained i>ericds and roiiiovcd v/hile act, certain Btrcs£08 occur v.'hich cause a reduction of strerj;;;;th \vhon cor.iparod to the anheated controls. The throe i;nhoated varieties vritbstood forces ran.rp.ng froia 44^000 to 55;0--'0 pyi (rounded firures) whije the heated samnles of the same materials rau-ed froii 25^000 to 52, COO psi. Tnia represents arproviinateiy a 4C>^ reduction of strength in the heated samples. On the other hand, \,'hen the heated eairples '..-ere £llo-:;ed to cool in the oven, aa eho-./n in Table 9, there was an increase in strength awou^rMinG to approxijiiately 23;% for obsidian and MQ% for the iiiiih Spr:inGG chert. Cohering I;he material v/ithout the int3:'Gduction of stresses allov;ed the heated scruples to resist failure for a longer tii;ie than unheated counterparts or heated epeciniene "^hat nad been streGsed by sudden subjection to a cool environnent. ho co;:^parison should be Liade betv/een the pounds of preesar.^ per square inch recorded in 0.'ables 8 and 9, TliO experiments wei'o conducted several months apart, the equij)raent v;as operauod by different individuals, aiid the rote of load i/as not obscrvcc: fc_ the saiiiples removed freu the hoL ovejn aiid th-jir controls* The rate of j.oad for the Table 9 samples u&i^ approxireately 20^000 pounds ]}er iiiinute. In addition, a.nd rx>st iinportenbly , blio sa/aples ^vere different. The obsidian sanples \
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66 both of those speciraons as obsidian based on certain arbi-trary attributes shared by both; the use of other attributes !?.a:y have resulted In a different catoGcry for each. Of si^';nificance here is the reversal of the aricujit of pressure need.ed for fracturing the material depending; on uhether the rock v;as roriioved fx'Oiri. a hot oven or v;as first ellovved to gradually cool in the oven. A ji:3; vms machined to apply stress to the ceres as described by Reiclu.iuth (15'o3)o Tb.is jig •.•as used in connection with tlio Hiehlo Universal testing machine oescjvibed previously. The jig v:as constructed to appj.;/ point tensile lead to the curved surface of the cylindrically cored s-;:eciiien v'ith xhe long axis of the 3j)ecir:en placed horizontally and at ris^ht an^jles to the loadin;^ jig. The J:^, v'ss constructed so that the point compressive loads v;ere applj.ed throuph s;:\all diameter steel hardened dov/el pins vjith rollers nian\-ii;'c'^;turoi by Holo-Krome of Meet Hartford, Cornice tic ^'.t (see li'ipure J^iv). The cones of percussion induced at the points of apr;lication of conpression produce internal tens-ile stresses perpendicular to the load axis. Cornd sa'Jiples.; one inch :in diar^eter of varying lengths vrere prepared as descx-ibevil earlier. In the first experiv.cnt ^ tvo cored speciinens of Ocala che.rl v/ere heated to ''00*' C for 2^'r liours and renoved immediately frora the hot oven at t'ne end of the heating; period; tv/o ya:nples v/ere retained as i.u-jheate-:' controls. Tb.e results of tiul s

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67 ^

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68 e>:poriraont were as follows. The iinhoauOil Ccala chort vn.Vistood Torcea o.verar;;in3 2700 psi ^vhile the rioated Deal a cher1 v/ithctocd forces avGraging l^'^^O psi» This represents s reducticr. ±n fores '\^'^ '45/-^ noodoci to brsalc the ic^nterial. Tho point load tensile strencvfch vai^ cciriput&d frcj.i the follov.ir)£; eii:pii"ico.l expression i^lven b^ --^oiohmuth (1563): T = tensile soren^th F ~ total f ai Itire loed 11 pounds D =^ ooi'G diaivieter jn inches TliO inforioation to be gained froiTi point tensile tc3t3 v;as considered pertinent to this investigation "beoau;:^; vbe aruonnt of foree used t;o induce faij.ure of the i-iaterial "bv point teii3i]-e stress is effsent.ia3.lv the sane as the igtren;;;th needed to induce fracture ivh.on iianuf acturinr liahit tool3 iron siliceous materials ov either percussion or preaeur-c riothodo. Therefore, extensive experiiiionts uere sel; V.V to test the point tensile strenpth of differin;;; 1, Four samples of oosidiori, Hi^h Springs chert. end. Johnsorj Lake c};ert ^vore tested ss lollcvs and allov;ed to cool in th.o oven: 1 S'.'j-iple of each used as controls 1 saja:;le of each hoaced to ji^GC'O for 2'!recurs 1 naiiiple of each heated to 3^0" for 2'-\hours 1 sample of each heated to ^lOO^'C for 2-'! hours 2. Tv/o ssuiples of obsidian and of Jolmson Lake ^)lJlt (fioia sane core as Johnson Lri3;^e chert ut.ed ebove)

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69 were heated to ^GCC and J^O^G left for 2'-!hours, n,nd then rei'ioved ii;jaediately iron the oven. The results of these tests arc z'^ver; la Table 10. "in all aam-^les except obsidia?.\ for vrliic)!. bhe data './ers not ronsistent 5 there itt an increosinn; reduction in stren-;;th '^;ith increase in teuiperature. In addition, thcuf
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70 C) fi •.'> o o v^i 03

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71 strength '..'hich occurs v;hen spejcinens are removed iiL-nediatslv Tron the hot oven is due to stresses resulting v;hen the ir^aterial is exposed too rapicly to a cool onviron-.^ent, Tv;e3ity-six x-raj diffi^aotion patter:i3 v/ere run on J.J different sarnples oi' heated and imheated cherts. Ho con^^dstent difxerences could bo detected indicating thot ;ao change in the cr;ystal lattj.ce occurs (see Figure 1-i). The slight difference shown is vrell within the range of experi•He2:ital error. If the crystals \;ere coarser , the peak \;ould "bo iiigher; if the crystals xvore finer^ the peak would be ].ov/er. Differential Thermal Analysis „ (JJl' A )_ The method of studying icaterials by differential theriuiJ. analysis consists of heating a small, finely groxmd sample at a constant and rapid rate, ancl recording by 3\iitable means t}:'.e endothernic and exothermic effects, A difforcntial ":;heriiccouple is used to detect these effects. One of the taerraccouple Junctions is placed in the sample being studied anc< the o!:hcr is sot in a thcr^^ially inexl: substance that is undergoing the saine heat treatment as the sai'ple (Berkelharaer IQ-i-'!)' J^'be electric current generated by the differential theruccouplo i.s a'\plifiod and recorded, Jli-idotherjiic peaks result if the sanale is taking on energy. BaraiJies were prepared of puie qu^;rtz, pure opal, heated and unhcated Johnson Lake charts High Springs ch&it.

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72 ^ 1 i

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73 OctJ.a chert, 2n-;;~j.:i sh flii^it, and obcidi.-.in, Arr-^pgenents v;ere rtade v/ith the Soi.Ls De^/arbii-tnt at the Un;Woic-.i.tv of Plo^:^ida to 'Uoe the differential theriaal enalysis equipine}it , The ros-ulta of this e::];crir;eiit \:cTe e;:cour«n;ii;~ since they substantiated data cbtainGd iron the vrei^ht lo;;;3 experimont. As the 3a:i;ple taJieG on energy (hGat), ^-^lauer is driven off. This v/as apparent by the ondother'^ic peaks at 112"0 as shewn in ?iC:;ure 15 for opal ^ John.^on Laha chart net pre-viousl;^ heated, Ocala cheit. and Englis!; fliivi,. This v.'a.s due to the removal of the adsorbed waiaar heJ.d on the surfaces of the nicrccrystals. In the aura quarb^; scua-p] a 5 the already heated chert aa-nplaj the High Springs ch.ert sa):ala, and obsidian there iJ s no peak at 112~'C. O'hasa natarit'lc have already been dcvolatilized or Inhere is no noiature to arive off. The only cmoinJy thao seaas to :;xiat is thab tr'.o chart frora }Iigh Springs v/hioh Is Cli-;ocene i'l aae did not shov/ a peak at 112'^G. G?hi i; iriaterial is r;oro ccersely crystalline than ri^ch of other Tlorida iiiaterlid„ This fact is borne ou'^; by the qnartv; peak at 575"^ occurrinp with this sa;;Lple and the p'xre quarts ssiiiple. This peak represents the a],pha--be-Ga chan^^p? in the crystal lattice j and it is irajadiate as the sharp pea'? iraij.cates. This inversion reaction is rovansible in heating, and coolia^. Tc check the validity of the endothari.iic trend baginnins aboat r;:30''G-^;C0^C (see ^'igure 3 5), additional sa-aplev-7ero prepared aiid tested as before. These t.iaterials v:ere rerun tc det'oir-arine if the endot:\erraic trend indie atinr-.; an

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! 1 • 1: 1 :

PAGE 87

75 l.;j.crea3e in energy bein-, absorbecl noy have been due to an •in3l:ruii\eiital error. Excer.t for the absence of tho peak at 112^0, the rerm> nateri j.ls e>chibited the sou;a type of cv.tvqs as \:ez-
PAGE 88

76 Three additional slides cf Joiinoon Lako chert; \vere ground to Jj/. ^ vrhich is standard petrographic thiclaiess, to deternino if ther;nal atressos coi/ld bs detectec vobich nay have been generated i/ithin the i:;3?ain by the application oi heate At a nagnification of -s^OX no diirerencos v-ere observed for en vnhc'atod control, a specimen heated to ^OO^G and allov-ed to cool in the oYc>n. and a specimen heated to '^lOO^C and removed imjoediately froiri the oven to a cool envii'on ment (see Figure 16), I'hus , despite the fact thot strcngtb tests repealed a siraiificant reduction oiincT-.^oase in stT-ength between heated and unheated cherts ; and that point tensile tests indicated^ there is an even greater reduction if materials are removed iirmediately frc2,i a hot oven, these chsnges are not observable petrographically. jJ£P-g-!£.-^'J-2-h£^!'"-:J:."^ /^^^ Sn eci fic^ Si.u-face Are a The method involved in determining the surfece area consisted cf the gas absorption techniqae in \vhich heliiuj, is used. The data v;ere analyzed by an Orr 3\ii-iece-Arca ForeYolui/iO Acaly^er. Pour sauiples vrere subnitted: ?Iigh Springs Ollgccens chert v;hich is coarse grained and gave a quarts Tn'vOJ/sion poah on differential ther!oal analysis, Johaison babe Eocene chert v/hich is fine grainec , and Zocenc chert frorii north of Ocela-— both heated and nnb.ei-ted. The results of the tests on the i/nheated cherts v/ero consistent xvith thei grain sis-e end packing. The least soccific surfece area vas 4.6^:rr/g for the High Springs chert; 'y,y9 rl^/g for the Johaison La]:e chert; and •'I.SG H'/g for tlie Eocene chert

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11 unheated heated Figure 16. — Petrographic Sections Showing No Detectable Change in Heated vs Unheated Florida Chert (Scale: 1 inch = 1,500,000 i).

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78 from Ocalcv v/hocc crain size is interiuediate of the three samples* Host significantly, the Eocene chert fron Oca] a thao }'c:d b'icn. heated shov/ed a rricrked reduction ivi the o p grr.na].-r si;rf3Co area: 1.90 ]-rvs conpared to ^'.86 I'^^/'s for ii.-?, VLnhoated connte.vpsrtc This represents approxinatclj' a 60>:i reduction in the £,ranular surface area of the heated cherts There is no qvostion hut that tlie Kicrocrystal],:i;i: :;urface area has been reduced in the heated scacinen. Th J s vas due to the roductien of the intert^ranular pore radii. In other words, porosity had been decreased duo to o fusion 01' intergrovvth of the ;';rai2iS» A coiJiputcr pi-intout sho;-;;rd the sl;;;e of tl^e por-e space distributii on and surface area distribution relative to percentape of occ\;rrence. The ploL for C'cala unheated chert shov;ed the ndjU'te size of the oririnal pores: 27. Bl^^ of the pores v/ere 2'6vor snmller in sise whereas about ,lJl-','j v-ore 370.8,;.. §£§I!IilJ3il_5i^£jL^2SH;. J.li^ roscope_ The scanninr; electron jiu.oroscope (SIT.) is used to study aurface raorpholo;_.;y (Krinsiey and Mar^olis 19&8). S'^iall flaheo not exceodinp J/8 x 1/2 inch vera pressed froia unheated and heated cherts. The saraples v/ere cleaned v;ith aoovone and rt'ounted vith Scotch tape on an SET! speci;^ien plup. Three orfour specii-ons \-;ere -aounted on each pluf;. The freshly fractured surfe.cos v;ere exposed for scannin.^. Tb.e sreciriens \;ere then coated v'ith f';old "in orde.to nahie the surfaces a bottcj" conductor forthe

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79 electron beam: the i;eclmique does not elininate or create c.ny additional surface features" (Krinsley and liargolis 19S8: ''+58). Heated and Uiiheatod sair-plc-G included -iilicified coral, Ocala chert, Hi£:h Springs chert, and fine and coarse j^irainod JcTmscn Lake cberb. The cpocinens were placed in a CaDbridt'ie Stereoscan electron laicroscope lioi^sod in the Department of Ketall-urr:y on the "University of Plorida Canpus, I'-i-G entire irac Lured surface ox each of those specinens was scann-d. Piauras 17 and 18 shov/ the typical surface topography, draiiiatically illustrating the changes ivhich occur v'ban cherts are heated. Figure 1? is of Johnson Lahe cliert (lOOO::); iM.r;ure 18 is of silicifiea coral (12,2GCX). 1)1 the unheated specj.':-enc , the individual grains are seen looking like so .niany hroad crumbs. Sorae fracturing has occurred through the individual grains hut inoi-o frequently the fracture goes around the grains. In the heated speciiiGns, the fractures pass through nost of the individual grains; t;j.at is, the individual grains are actually split, and the fractures contiauo on passing thiougli tlie interstitial-areas vhich are nov/ piora finally cen.ented. In other vroriS, >a-en fracture occu:-s it alternately splits and nassos thravgb succeeding crystals and iiitercrystal areas in its patb. until it ter;:i3 nates. This accc\ini;s for the snaoth surface in the heabed s"^;ccimens.

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80 unheated Figure 17. — Surface Topocraphy of Unheated and Heated Johnson Lake Chert Samples as Viewed by the Sganning Electron Microscope (Scale: 1 inch 25^^000 A).

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81 *^' imheated heated Figiire 18. — Surface Topography of Unheated and Heated Silicified Coral from Florida as Viewed by the Scanning Electron riicroscope (Scale: 1 inch 20,520 i).

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AliCHAEOLO^ICAL ArPIilCA^ION If an archaeologist sucpscts^ that the chipped stone remains he recovei'S fron a site hi^ve teon tbernialjy altered , it would be cesirablo to subject these r^aterials to a ztBnd.ax:C±z2d. test in Oi^lor to elii^iinate bhc "gueG^" racbor. Thif, 'J s i::LrortsJit c>xn.c~ x;hernal alteration rreF:ente inforijatiorj ooncerniny not only stone technclo;jy, but contributes vltinately to a j;reater underntanding of prehistoric nan's behavioral patterns. ibis becciaes even rore val'Aable if an investigator is ivorkinf^ on tine levels v.'hcre crip stone artiiacto have been preserved. The follov;int' disciission involveiy a review of the Trsaiij e:ri.-erijnents ccuiducted tnroupbout the course of this atadp to detor:::ine i-" one or i:ore ol these ::if:ht feasibly be applied to site materials. ?or a fuller account of these f;x;.'erii;ents , the reader is advised to refer to the section on ilethodolcgy, V/ei;'ht loss cannot be used as a criterion to deteri,;ine if specimens had been therKially altei'cd because c:cperirient3 daxonstrated thaL heated specimens tended to take on raoisture aa^ain. In otb.ar v/oi'ds, if £ji a?ehaeolo'iist vreiG^hed, heated, and rev/ei^^hed outcrop natorials alcnc •.;itl! site :.aterials to check differences in v/ei^ht loss he probably would find no sipni.ficant difference. And even if 82

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83 he did, he •..•oulc have tc use the results ver;y cr.-jt;i ously since he could not be abc.olutely sure that his site racteriol v;ar. identical with the outcrop juateriyl. Chert will vary cOiisiderabl j even v/iLhii' the oaiie nodule. };irre./entiol thei'iiia]. anal;;,'r;ii. prohabl;;; vould alec reflect this tendency of the riaterial to tcl^e on moiyturor If storie reii.ains are found v/ith '"potlid" fractures or fractiirea n^inua bulbs of percussion, it nay be said that the stOiie had been fractured due to expauoi.on oicontraction resulting: frorji heat^ but there ^.'o;ild be no sure \/ay of deter:^ininr; if the eirposure to the heat had been intontiona], or bc:cauee of a forcat fire or hearth situation. Standard rock laecherJoG tests ni^ht be of vaD.ue to test site npecirnens v-i1;h outcrop materials, but it probably v/ould be iupoasibie to recover lai-ge enough npeciruens frciu Eito!^: to prepare ssinpJ.es v/hose dipicnoioa;: nust be precisely accui^'te in order to a^eure tin) validj.ty of the resultc, Thua, this iiiethcd succeeds in theory but fails in practical application. retrc{;jraphic analysis revealec ro chan{;^e in the size, shape, or orientation of the individual ::iicrocrystal£ . This V?::: borne out bv the x-ray diffraction pattern ivhich ahov;cd no choupe in the crystal lattice between heated and unheated i.i-'terialse The vitrcouaness of a surface ijhat has been flaked subsequent to th';r^nal alteration offers^ perhaps, the most valid indicator if^' t ti.fr: y-r.thoa ^le"^; '^e^^a 0'"p]oyodc

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8^1 YitreousnoBS may not be coj.niletely reliable, liov/ever.. Several brolion BpeciniGiis v/ore selected from precerar.ic levcjs (>2000 BC) of a Bite (A-^55) in Floridc;. These speci'nens ;;erc chosen beco.uGG their outer si.r faces v/ere GAtrericly lustrous and so;oe exhibited a pinkish cast. It \-:as suspected that all had been thermally altered. Snail flahes v;crG pressed froii each specimen. One speci:;::en which / -d an especially n;reasy li-ster on its outer siirface v/as \or;y diificult to flake and the frecbly flaked surface v.'as dull. Tills v;as a disappoiiiting developJi-.eut -, because y'c v;as horded tliat by reinovinr;; chips from field speciraens^ it rji:;_;ht be deteruined that vitrification I'^hich penetrated the cni.ire i^iass of test laateriols is a periajment changje and id.f^ht be useful for archaeolOjpicel intexr.-retaticn especial].if local outcrop materials are not naturally vitreous. Thi; spec3i;^en had either patinated subsequent to thermal alteration resultinrr; in a rei:>lace:neTit of the iatern-1 ?uster5 or soil conditions due to lon^ buria] had operated to form the greasy luster on i:ho cuter surface* The former explanation io ::iore plausible bocaai'e often naterials that are not iDstroua will be recov'ored from the same location as lustrous neterials. If soil conditions v;erc responsible for tlio luster, then ell speciiaens should be affected. In ercaminin;; a representative sample of flaking debris or artifacts tha'c are suspected of being altered, r'U J nvestigator should find a number of specimens which exhibit a 7.-elict dull area surroujidcd b;/ ex!:reme vitreousr^^-:'. T---is situation su.>Tcsts t'^-\t ';';: d\ l'!. area h-;s not

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been flaked rsuosequont to heatin^: wheroaG the vitreous area hns been (see rip:i,ire 19). Soil conditions v-culd not produce this tyj)e of differential presej:'\''awion. Color c-ianv:£ :-hich ccci'r^ at a lov/or teniferature than the si^;nificant ctiange reciutinr: in a greater ease in flaking, laay be considered a reliable indication if e.ccorjpanied by vitreouGnesG. One other sv>3r;e:.tion is appropriate. If local outci'Op n^atorials differ in te::ture from site speciriens, it is a 5inp]e task to heat the local naterial:-, fracture the-uj and deter:;;ine if tjie resulting: surface reseijjljles site i:-iaterial3. This is hov: Kr. Grabtree fii'st suspected the therrr.al method liad been employed (see Literature KeviovO.

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86 CD rH > CO CO CO ^1 TZJ -P •H ^ CO O -P P^ -P CQ CO ch p a; o d H p o^ d •H CD 'H CD CO ;^ ,Q CO (D J3 CO > CO o •H fl o o ch a to (!) CO CO fH • G 0) P fl fH X o •H P OrH t>l CO
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SimiAI^ AND ING;IiRFAc.^.-i;:i..;.. DeL;pjJ;e o.oroQs.tory coHiij-ents by e^qj-eririeiitcrs \^;bo have ••proY=:^3" i-hat siO^Jecting fl^nt >:o fire bai^ only destrur--tive ^fleets (ocg.. , Fond 1950; i^llic IS^iG), srcii,^;h firothav^A aocouixoo exisi; (e.g., Schuiaacher 1BV7; Powers Jo??; l^oii 1035) -o v/;:;.rrant investigation of tbe fcechnicue« i5vi;c;nsiv8 erpcrJ.n&Dts ccnducted throru^hout a tv/oyoaj:period, in whicli iiint matcrialG v;ero expcoed to heat under Jiij.iorous diverse condit j.ons , hcivo dc;aon:^br^.i;od that the altci-ation ci siliceous rocks ^ vrberi critical tuLpTcratur?.:c are reached slovjly and laaintainoa foi a susuaincr! period, probably conferred iox acvantage to prohiftorio nan in r-anuiacturinf: his chipped store inip].'!::;ant3, !i^ho oft--qvioted raethod of drippd.ap cc-ld uater on hot roohs has boon largely responsible for dieoroditinf; firo as a contributinp factor in ilintworkirii^ technology. Atte:;ipts b^ this investifjator vo ''chip" \vith cold v;atar produced no flakes ot all and resulood i/^ a cra^inj^ of the rock thus confiriiijnjjthe findinps of Pond (1950) and hlli is (19':0), Ho'vovcri if one rctnrri^. to tbe reports of Schu/fiacher (16??;, ro;-;&rs (16??), and Man (1S?^3X they report reisovai of rocks iron a hot fi3;-o after nhich tricy are shap&d into iiiiplei^ents. xhe only objection to these aacoL^nts jS their brevity* A mere detailed description or closer

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88 by those authors cay have revealed thot the stones vcre Kot yuhjocted to an open f ire , that they vie.j ha^-'e been buried, or that they may have been allov/tO. to reri'.ain in the Jieatinp; environment for an extended period of tii:.e. Ey inve3tit;:ationy have shov;n that: J.. Haterials removed fron a hot even did not xracciTre v.'hen exi;osed itiiifiediately to a cool environneab if the toiupc nature nececsar;y to effect an alteration in the rock had been reached slo^vlly and maintained for a lor^;; eno-U£h period for the procops to be corapleted. ?.. Under point tensile load, a r^reater reduction in strenj^rh occurs v^henthe rod: materials are re;;;oved iraii^ediatcly iron a hot over to a cool er^vironinent, Linited tesi;fi f/;ave results as fcllov;s: materials heated to JpCG but allowed to cool in the oven had a ^Oy'} less in strength over the unheated control. A sample fro:-;; the sane nodule v;hich had oeen heated to 350" C and exposed iisnediately to a cool environrr.ent had a G5;j loss in strenf^th--"an additional reduction of 2^/^, It is possible thar; for certain cxtreraely inojastic rocic tyxjes exposure tc these increased stresses ^;as desirable to make chippin:; aasici. !^'he accounts of. the above-n-entioned reporters are probcfoly accurate as far as they -o. Their descriptions, perhaps, have bean Bn.sinterpreted none because they are incoiapleto rather than incorrcci:, .Another objection which ni^ht be raised ;vit}'i regard to pri':dt:.v<' lam's /ler^ti.ni;!; of ;-ocks vjovlc. be that since he had no th_ . . ', ; , }ie had no way of Icnov/inr: hovv hia;h Die

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89 teyape i.'aturcv;as. This v;ou].rl be aliiiofjt as riclic ulcus as saying that be had no conception oi tii.ie becau.se he hadji't invented the v/atch„ Besides, tliese investigations deracn-strated that, at least for Ulcrida oli.erts, t!;-npc.i;'at:u::'es betv;een c^pO^'C and 600'^ G (a range cf appro:.ii:iately 500'^ 1') \^oalf'' effect a deoirable altera'cion in i:ne material. Thnt ia^ as 2.cnao the elevation of teniperat\Are was gradual, thvjr-o v;aG no increaaad case of chipping at GOCC oven that of 33C^C. laiile there is no apparent increase in flaking eaae^ liowever^ quite often attenpts to chip flint naterials that had been heated to "pOO^ C-eOO" C or had been heated to 550^C-''rOCC and removeclii.^uediatelj from the hot oven, resulted in a lateral snap due to end shock, fhua, there is additional strength less v/ith increased teni/ei'atures or increased stress. This fact \:as supported by point tenaile strength tests. Belov: J.GO'^G a satisfacrory change did not occur in Flcrila cherts, haterials v;ere not tested above 60C"C (approxiii-ately llfCh) because the aborigines probably could not reach or sustaDU such hir;h tenperatures. It re:::aJ.as to deter;";^in.e if the three ii-ajor problems tc be iity'^^'-tij^ated in this study heve been successful. ly solved. 1. A desirable chvsii^e does occur \7hen Florida cherts are theriiially aluered resultiny in a stone that is easier to flake than nts unheated couatc-rpari;. Mo sbruc!;ural chaa[;c occurs in tru;i. the si?:e, share, and orientatien of the individual inicrocrystals reaaln the same, but throu:3h the reirioval of interstilial v/ater, tlie nicrocrystals are riil J

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90 c? osen.' tO;2iether when certain Katerials other t-'naxi SiO^ so'^-ve a3 fluxes* When the flav; is introduc^;d v.-liich is prelininary to yad necessary for fracture to occur, the heated rock responds more lihe ^laGc than a j-ock azs^'^i^^^<^ ' J^j^ other vrorusj crysta}. boundaries are nc loncor intcrferin:;; -ith tbe ra^uoval of f lakes. G'hese staterionts have beer substantiated throughout tfiio dissertation by rcch r:ochanics teats, scanjiing electron microscope illustrations, analyses denonstratinp; a reduction in surface i;rea of heated materials , as \rell as intuitive observatiojis and exoerinents. 2. Prehistoric peoples v.-erc aware of the advantages conferred by tlierually altering their lithic i'later:^ tils because "che GhippinQ; debris recovered fron archaeo] o:;;ical sites hss been intentionally flaked follcv;inc subjection to }^eat. 7'hi3 is apparent because the fL^kes have bulbs of perciisoion v^hich doiiionstrate that there has been a poiiit of impact. Bulbs of percussion are not exhibited if rocks o,-^:.dode vdien too rapid, heetin?; or coolln^; occurs. Instead, there are "potlid" fractures or conchcidal fractures v;iiich do rot shov: a point of iripact. The fleked surface of the altered ;a eciMens are extreuely vitr'^'Cis , varyin^^ appreci-Tihly fron outcrop samples of the same materri.als. Very often also, due to the prosi^nce cf ::^i'\ute ar.oirnts of iron, there is a color chanye froi:; :-,rey-beiae-bro^«.i to pink-red. V/nila color c:uai3e occurs at a lov;er toiup'orature 'c\\s.n the siijjrificant chan»];e resultin[': in easier ilakj.nr; and v/iJa, not accar at all unJes;3 iron is present, it ir\oy be consicered a re2.i-

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51 A reviev; of available literature lias irocovei-od nvciorcnz accounts of the v.3^ of lire as an aid in the chip"piri-.;^ process — at least (•nou^:h to vjarrant the co.^-cliision that pvij;.i.tive peoples knev/ that fi^ce v;as capable of producinG a desirable cha:ia;e in flj.nt materials, 5, "ho problen of reccni:;endi::.Q; an easy test to deter mine if. riaterials frorj archC'eolor;;ical site? have been i.utentionally altered has not been very rev/ardin^. Test after test has not sUiXj^csted any really reliable criteria. From an exaiaination of a representative sample of flaking debris, hov-ever, an investigator shoiila find a nuiil/or of specii/iens exhibit.i.nr; a ro3.ict dull area surroundod by areas of extreiae vitreousness. This situation stronp;ly suggests that the dull area has not been flaked subsequent to he at in f, v/hereas the vitreous areas h.ave been. The evidence presented in this report leads to the conclusion that the manufacture of chipped stone irnolciiients is easier to execute af lithic materials are first cauticusiv su.bjected to critical temperatures (?^C'*G-'-CO''C for Tlorida cheats) fo2' sustained periods (1?~?''hours but varying with sa^iiple sise). After nearly tv;o rrillicn years of exaerinentation vn th "Tire and stone, it should core as no surprise to find thai: priiriibive peoi; les v;ere veil av/are of the advantj^C^^of theriaal alteration. Artifacts have alv;a^s been the arcbaeolocist 's best friend. A recognition of textural chanpes occurrinr: when siliceous mater:lals are thermally altered provides knov/ledse rolat.ivui to j.ith:ic technolo:,jy ejid privnitive man's behavioral pat terns, thus sstablishinj" a nev; diiaensicn to archaeological ivicerv:)retatiou .

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'^'j 1 BL 1 0:3ft APM Y 1961 Ans-loQi^ in Arcliaeolorical Interprebation. Sg-uthwe stern Journal of imthropQloF^j , Vol, 1 ? ^ pp/" 317-23. Albuquei-que ." " BERKELHAIli^^ , I,CUI3 11. 19''i-'!Differential Thermal imalysis of Quartz.United States Peparti'ien t of the Intei-ior, Burea u of Kines ^ r^S !J^iiL.21i.§:^5ZIi£-jl££» ncGraK-H:in Book Co., I^ev^ Yo'rk . "" BliAKNCN, P. A. 1909 Aborif-vinal Reraains in the Kiddle Chattahoochee Valley of Alabama and Georgia^ American Anthropolop;ist, Vol, 11, !Io. 2, pp.'l8&^9B. Lancaster 5 ' Pennsylvania, cock:;;^ c. v/yi'iiE 19'15 Geology of 71orida. 1-Tcrida Goclogical Survey , G ;?0i 1 o ^; i c a. 1 3u J !1 e t in , li o . 29. Ta 1 1 ah. a s s e e , C:U:irA:CJ, DOK Y.. KWD B. IJOBERT BUTL2R IvG-';]:>iotes on Ex:peri:aents in Flint !iiiappinir: J. Heat Treatments of Silica Kinerala. j^Gbiwa, Vol. ?, •'o, 1, pp. 1-6. locatello, Idahol ;jr.-.i.d., J. ", • • A v. riLi.ili -"'•• --^* T2iJ,yi?J^.!lL.J^ill££2Z> ^'^' AFy;L"TR"65-115 Univerr^ioy of UXinX^is, Urba^ia. iS'i-Oa riJnt-Vorhing Techniciuen of the American Indians: A:a Ex3)eriiaental rl^buJj. The Ohio Histc^ric al '^^ociet }; ubl ication , I'^o, V?. ColuHibus 19'5Cb The Possible Cultural Aff"'' : ^ ' :-'"at Lis:: Caches, Chj.o__-Aoch_.ieolo " 'c::-! guartorlY, Vol .'"^V rpf-" -' ^^ . -— -""

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1952 A Study of the Texture and Coraposition of Chert, Ar.Lerican Jourp-a.l o f Science, Vol. S-^O, np. M-S&510'. ile'w Haven. F01/Ii:Ev GiliiAi^D 1696 Stone Art. Thirt eent h Annual liSi^ort of the Bureau of __AaerJxan £th:plqg-// . for the years TST^-^r ??'" ^!-7-l?8". Washington. 1910 Autiquitieo of Central and Southeastern ilissouri, 2lii::£2Ai_iii Arae ric an Et hnoloa;Y.|_ Bulle t :ai » Ko. 37. Washington. GSEfcii^, H. W. IS'i? (v;-iartz ; Extreiiie Preferred Orientaticn Produced by ..-innealinr;. Go i once , Vol. IS?, Septeinter 22, r> p . 1 '' ;•''' 1— 7 . 'v a E h i n g t o n , HAI-lKATl?, HALLS TT H. 1970 A Paleo-Indion Butchering ICit, Ajnerican Anti entity , Vol. 35 » ''o, 2, pp. 1-11-2.. Salt Lahi Cfty". HOIhES, ;. H. 189:> Stone Implements of the jrotoriac-Gnesapeake Tidevmtor Province. Pif teenth Annual I?gyort of the Bu reaTi of Aiiierican ^^thagloGy , pp . 3-1 '>2 , Washington c 1919 Handbook of Aboriginal American jintiquities. Part I. Introdiictory— the Lithic Industries, Bureau of iuaorican _Pthn.olo gy, BullGtin , K o , 6 C^ Washington. KSHiaiOP, FRAUZ AND HilNSJURGPII IIULLnlri-BSCK 1969 On the Significance of Impact Marks on Stone Objects Concerning Practure Mechanism, Glastechnisch e Ber ichte , Vol. ^-2, No, 10. pp. '43^j_/; g , Prrinkf urt" Am Pain. [In Gerinanll K:^TPSL:';y, ^/.vii) mi:) statipsp kapgolis 19<'B A study of Quartz Saaid Grain Surface Textures v.'ith the Scanning Electron Picroecope. Transact ion -s^^o f _ tjie _Ee \-i York Acad e vx^c_f Sci en c e s , j)-p. hy'/~77~ -fev York, LUTTCP, R. J. 19^9 Sj'-stematic Mapping of I'ractui'e Porphology. Bul leti n of the Geol ogical _S o c 1 e^c^r of_ Aj:ierica, Vol. 80, Po. 10, pp.~20Gl-'$,~ Boulder." HAN, P. H. J.803 Cnt>ie Aboriginal Inhabitants of the Andanan I s 1 ^n6.3 . The J ourn al of .th e /aithr orol ogic a 1 Tnst it'i t e _of Groat "3ri tai^f'and . I re^ and , '"Vo l7 2. 2 , nr: , 37'"J"91 = London.

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KaOOI^;, 0TI3 T. 1887 The Ray Collection from liupa Heservaticii. Aju years lScG-7, pp. 205^9 ^ ' Washiuiston. 1895 T!ls^.O;^lS^ns of lavontion, Il.l.T. Press. Cambridge 189.Indian Jasper i'.incs in the LoMr;h Hil?.s. Auerican hIl^}l££LQl.flill^±i Vol, 7, pp. 80-92. V/ashingtonT KlJJ:>;K;j.-f..i, 5 A. H. ^9-1-6 A.. Col or ITotation. Ten^;h 3dition. r^ffisell Color Co. , Baltimore. Ni^l.'I. CiiAi:iL;IS I-l. 19''i2 Principles of Struct-gral Gooloj-y. Third Edition. Jolm yiley ancI~Sons /Tnc~"' "London. 0AKL^-;Y, KEhlTETH IK 195? Fire as Palaeolithic Tool and ',;eapor'., l^L^^^Sil-'iP-i-ISS oXJ^2£-.JC2;£lii?it£5±lJi^ie^ Vol. 21, Poncionr PETTIJOK::, ih J. -'-^'•"^ Sediireiita.L';;i^^_RqchB. Harper a^id Brother^ Puolisl'ierCj ifev; York, PCNU, ALOXZG y. 13'^0 Priritivo Kethods of V/orkinn; otcne: Based en iixper indents of Ilalvor L. Skavleu. Logan huseui:: ^.^il.l^tii^ » ^^^ ?• Belcit. pc'.:l:;{oi Gr:^PHPN 1877 Tribes of California. Contributions to Horth American Ethnolop;:/, Vol. 37" Chapter XI, p. lO-'i . Vv'ashin^iton. PRESSLd:^, ]^. S. AhD v/. L. SHSARKH 1928 Properties of Potters' Plints and Their Bffecti in V/hite V/are Bodies, Bureau of Standards Technolor:ic Pagers , ho. JlOV'Vol. 20. 'pp„ 289~;5i5, Was Viinguon . PP83T0i;, P. -.!, i9?8 A otu.dy of the Pvpture of Glass. Soviet j of Glass Ttechnoloi-y Joiirnal, Vol. 10, rn. 23?"&9. ""bhof field, Engl an d . KEIGHhPPH, P. H, 198r3 Correlations of Force-hisplace;::ent Pate with Physical Properties of Rock for j ^ '-e PrillinfSysteris, Pro cced in^:s of the Fif ^iu.^:^ of Stud^^ on. Rock PechariicsT"". J^V" 'The' J-hj.hLij ..n Ooriic^n^^ " Kc\;'YorP:.

PAGE 107

Qr3 SGIillALZ, HOBERT F. I960 F].i3:t arjd the Patination cI Flint AriifactG. The Prehistoric Gocleoy , No, 5, pp. ''i-''!— 9. Lo2idon. SGIiUPAGlI/;v, FAUL IC'V'? liothocis of liaking Stone V/eapons. Bulletin o.!' the U.,S« ^g<^3.o.^ic ard G eof ':r &ph ic _SurYe:/:_o.f the Territories^ "Vol, '^^.j pp. 5^^7-S^ V/ashington, SEEPAHD, EDl/lK M. 18'/? FepoGit of Arrov.'-ileads near Fishhill, 11. Y. Annual _F.ep or t of the Srnith.sonign Instit uti on , for the year 1376, pp." 507-S. '" Viashington. SKITii^, CKARLK3 E. 1885 A Sketch of Flint Kidse , Lickin£; County, Ohio. Annua l x 'eporb of the Sinithsonian Institution, for the year 18S4-, pp. 855-72'.'' V/ashrCn-^ton . TULLIS, JAW 1970 Quart 2. : Freierred Crienbation in F.ocl's Frcduced by Dauphine Twinni.nr. Sciorce , Y->1. 168, pp. lJ-^;-2--^: Washington, V/AILACE, EKKIiST Al^lD E. ADAn3Ch HOEBrX 1952 The Comanchcs: Lords of tho South Plains. University of^Oklahoraa Press", "Xorxiic-m. VFKF, H. 'U , D. v. BAKili, AND D, T. GSI-^GS I9'-'7 ^'---^ic.y Fabric iVnalysin of Hot-Vorkod and jlnncaled Flint. Science , Vol. 157? ?p» l''-i--l-7-9. V/ashington. \7II,&0I; , Tl-;Or:AS 1897 Arrov/points , Spearlicads, Ihiives of Prehistoric Tines. Annua l__ne port of t he 6;:ii-bhsonian Institu.-io: ]L\iL'~-^Liii2i2'2i._L.]i^^^ ' pal't 2, pp. cll-S^S, Wa'shinj-'tcn.

PAGE 108

3ICG2;iPHIGAT. SIoSTCH Barbara Aim Purdy v/as bor-n Aua-ust 2:5, l'->27 at Ssxi Die:;:o, Galilcrriia, In June, l9-'i-5, nlie was o-a^^ii^tod fro;-n Tlerbert Hocver Iiigin 3cl:.oolc In Juno^ 1943, she received the de^^ree of Bachelor of Art& v.ith a major in Zcolooy from iJ3n i)ie:;;o State Colle£;o. In IS'vS, she vjas G7iiploycd at Soripps Institution of Cceanogrraphy at La Jolla, California in the Departnent of harine i;icrohiolo;j:y. ]?ro;i 19-'9 to iSyS", she v;as or^ploj/ed in various departrjerito on the c-::::pus of the University of California at Davis. Prom i960 to l9o;^ :-?id interiuittently to 19-975 she typed theses ai:d jer^'ed as Ihesi^i Zditor at *.:ashiiir;ton State University, Fullrian, Washin£;;ton. In the fall of ISc-^i-, she enrolled in the Departj:.cnt of Anthrorolof-y at Vashinr^ton State University. Frorj 19^5 to 19&7% she v;as a liesearch. Assistant and reccivec. the iiastor of Arts dei::ree in 196?. In 19'^?, she er rolled in -uhc .hepartinent of Anthropolory at the University of Florida in order to prrsue v'orh leading to the decree of Doctor of ?halosopr..y. In July, 1969, she attended a four-voeh flintvjoi'kin^; session at Shoshone Palls, Idaho sponsored by Idaho State University vrith funds c-'^si:ited by the National Soienoo l'onnda"Cion.She v/as a teaching; assistant from 1968 to 1970 in the Departrient of Anthropolopy and taii^ht ATi-erican Instn tntioa'' in the University Colle;;^e at the Uni-ersity 95

PAGE 109

97 of raorida duriinu the fall quarter, 19/0 and thr.winte.i-' quarter, 1971. Barbara .'Vn,n Purdy is Eiarriod tc Laurence Henry Purd; and i;:; the aothor of four children. She is a Eenber of the American Anthropoloivical Associatj.on and the Society for Ainei'ican Archaeolorry.

PAGE 110

I certiiy thai: I have read, this study and that ±l. nj opinion it conior;na to acceptable standards of scholarly presentation 3?}.d is fully adequate, in scope and quality, as a dissertation io:r vhe degree of JJoctor of Ihilosophy, Charles H. Fairbanks, Chain Fro fe 3 3 or of .anthropology 1 certify that I have read this study and. that in r^y opiniori it coriforms to accey tabic standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. '"i 1 n -i nn r? . I^nl 1 nr^h . .' :<^ ivillian a. Bui lard. Associate Curator . }<'lorida Stcte Imseu^. 1 certify tliat I have read this study and thatin ^ny opinion it co.nforras to acceptable stanvdards of scholarly presentation and is fully adequate, in scope and qual.ity, as a dissei'tation for the decree of Doctor of Ihilosophy. 1 certif:/ that I have read tiiis study and that in my coriforius to acceptable standards of scholarly opinion 1 presentation and is fully adoquaoe, in scope and quality, as a dissertation for the d.egrec of Doctor of Fhilosophy, Harold i: . Brooks Associate Professor of Geology

PAGE 111

This diGsertation uas subiritteG to tho Dean of tho Golle:;;c of Arts and Sciences and to the Graduate Council, and v/as accepted as a partial fulfill.nont of tha requirements for t}ie dc.";ree of Doctor of Philosophy, Pean ," GradA^ate "School

PAGE 112

33 RU5 1142.6<


47
fractured surface is dull due to refraction and poor re
flection. After heating, the fractured surface is vitreous
due to the greater transmittance of light which occurs when
the fracture passes through successive microcrystals and
intercrystal spaces revealing the intragranular nature of
quartz.
If the material Is fine grained, it seems to alter
slightly faster which may be because, even though it contains
the same overall amount of water, there is less moisture
being removed from any given interstitial area. There seems
to be no correlation between crystal size and the tempera
ture at which alteration occurs in Florida cherts. There
does seem to be some correlation between the composition of
the chert and the length of time as well as the temperature
at which alteration occurs. The fact that Florida cherts
are formed as limestone replacements was discussed in the
section on Materials. Some of the materials tested appeared
to react differently than others in that they did not
respond at the same temperatures or time periods; also they
did not decrepitate or explode. Except for the area directly
under the cortex which always seems to be very siliceous,
a satisfactory change did not occur in some rocks at the
testing temperatures which usually effected a change.
When temperatures are raised slowly and left at
either 350C or 400C a change occurs which is very apparent
when the sample is subsequently flaked revealing a vitreous
fractured surface. In addition, it is definitely easier to
manufacture stone implements (see Figure 6a). This statement


88
by those authors may have revealed that the stones were
not subjected to an open fire, that they may have been
buried, or that they may have been allowed to remain in
the heating environment for an extended period of time.
My investigations have shown that:
1. Materials removed from a hot oven did not frac
ture when exposed immediately to a cool environment if the
temperature necessary to effect an alteration in the rock
had been reached slowly and maintained for a long enough
period for the process to be completed.
2. Under point tensile load, a greater reduction
in strength occurs when the rock materials are removed
immediately from a hot oven to a cool environment. Limited
tests gave results as follows: materials heated to 350G
but allowed to cool in the oven had a 40% loss in strength
over the unheated control. A sample from the same nodule
which had been heated to 350C and exposed immediately to
a cool environment had a 63% loss in strengthan additional
reduction of 23%. It is possible that for certain extremely
inelastic rock types exposure to these increased stresses
was desirable to make chipping easier.
The accounts of the above-mentioned reporters are
probably accurate as far as they go. Their descriptions,
perhaps, have been misinterpreted more because they are
incomplete rather than incorrect.
Another objection which might be raised with regard
to primitive man's heating of rocks would be that since he
had no thermometer, he had no way of knowing how high the


61
Figure 11.Composite Illustration of: (a) Drill Press,
(t>) Corematic Diamond Core Bit, and (c) a Chert Nodule with
Cores Hemoved to he Used for Strength Tests.


jPhsn,' cVadvob Sci.Ji


54
comparison plus the -bn derived from soakiny o; 1 lies >.-
a month in a mo i s o s _aa b a t h indi c at p t h at : t _i. n u 01 p o s: . 0.
to use weight (5sin or loss as a reliable1 criterion in deter-
Mining it archa o epical spec irons no been subjected to
heat,
Lo creed t at i qn_ and_ Expo axon
It vj3ls no mystery to print tiro nan that firr. could
be destructive to rock (see Li :. era tuce Jiovic-.v:) > out this
invest ira tier, has attempted to dc.Mens trole that v/ben
si?. ice our x- 0ck materia.13 are c outi ousl ;y .?u i: i -? c te d t o 1; 01i,
an aIreration occurs which conferred on adrart-re to pre
historic nail in the manufacture of his chipped stone imple**
mente, Kan had many thousands of years to discover this
f ac t a7id t o pe 1 f c c !- tVie tec:'ique Sinc ? t'i\o v.0s o i f ir a
and the use of stone v;ore tv;o of ubo earliest and most
impartvut :i tano in bhe inventory of a pivy3i0a5 !t:/ ond enl-*
tur ally evolving ere a.ture, it should come as no surprise
th.r'j Ive err dually acquired an inti mate knovrled^e of their
a l fc r 11' 0... e i... 1 h e ob s o r .'alione b o *0 c ol a zo-sse d b a 1 o v,f .v
probaV-ly mob. like those ro.dr lory op;o,
lb? Viator laic i:.Y\ circa in ih. no n>;.\ --/;. .out a v/ere :?
3?! 01 1 d' C b: ;r c 1U C13 011 S U i p;h I OC ? U V *2 t C. 1 ft o! oU (; t 2' f a 5a
tures, o nab at all, if otter rod' typer vero used. Sr f-
fici:'t ;j:ov1cc of *:r.-';'lo.1'ibr. ::afr 1.1 j.s wrr- .aot uvuilab.10
i. r> x* <; :oo ca51 -0 tb; rea0." 1 : vo1 ¡ 1 d ccr bala 1 y be ***! ':.tenin:;
bn -.' ; i "ubh or -iy 01 b1.?? b^ulosn
i. -\f -r. (') /;*:s. :rj. -;; ; ; v ?r0 :L- c .0 c... 0.r r-


60
time consuming,, a coring device was used which greatly reduced
the time needed to prepare samples. Using a drill press as
a basic piece of machinery (Figure 11a), a Corematic diamond
core bit having an inside diameter of 1 inch .005 with a
6-inch core barrel and 5/8-inch diamond penetration was con
structed by Anton Smit and Co., Inc., New York. This is a
variation of a Corematic drill used to cut holes in glass.
The chert nodule to be cored was clamped into position as
illustrated in Figure lib.
The diameter of these cored samples was exactly one
inch. The cored samples that were to be used for compres
sive tests were then sawed as close to one inch in length
as possible and ground to precisely one inch. This reduced
the number of surfaces to be ground from six for the cubed
samples to two for the cored samples. The cored samples
that were to he used for point tensile strength needed no
additional preparation.
Compressive Tests
Of the original twelve 1-inch cubes, six were heated
to 500C as described in the section on Heating Experiments
and six were kept as unheated controls. One sample each of
heated and unheated obsidian, silicified coral, and chert
from a quarry 5 miles north of Ocala^ were used for compres
sive tests. Compressive strength data obtained from the
cubed samples of Ocala chert were unreliable due to error
in testing? these were discarded. Subsequently, two cored
" To identify this material as to location it will
hereafter be called Ocala chert.


VS
Hirco additional slides cf Johnson Lake chert were
ground to 3ui which is standard petrographic thickness, to
determine if thermal stresses could os detected which nay
have teen generated within the grain by the application of
heat. At a nagnification of a OX nc differences were ob
served for eh untie a tod control- a spec icen heated to ,¡OCC
and. allowed to cool in. the ovan, and a specimen heated to
di!CC and removed icsuediabely iron the oven to s. cool environ-
asiit (see Figure 16), Thus, despite the fact that strength
tests revealed a significant reduction or increase in
strength between heated and unheated cherts-, and that point
tensile teste indicated- there is an even greater reduction
if Eateriels are removed immediately fren a hot oven, those
changes are not observable pe trographic ally
Dotemination of Snecifio Surface Area
The method involved in determining the surface area
consisted cf the gas absorption technique in which helium is
used. The data were analyzed by an Ore Surface-Area Fore-
Yoi us-'; Acalyzer. Four s arpies viere sub: lit ted : High Springs
Cligccens chert which is coarse grained and gave a quartz
inversion purl: on differential therms! analysis, Johnson
bate bocana chert which is fine gr airee end Socene chert
from north of Ce? a-both heated and urhoatoH '.The results
cf the tests on the un seste, cherts wevi. consistent with, their
gr.iin size "nd packing. Hie least specific surface area was
.CA I-Vi. for the high Springs chert; 3.39 ¡-Vg for the
Joidison L-.hc ch-rt; era.. 'l.PCi i'Vp for the Soconc chert


II
Houses (1919! 176-7) < -'tes ?ov:ue In o ini} r
descripcin of the use o.f fire discovered in another pit
at PIiiit hi dye, then adds
In y ene ralho e ver. i he nc t i on of f i r : > i o no & h rue -*
five to stone i an I if not very discreetly errpj oyod
will so fits* the stone as to rare it unfit for cost
u->o, TV'*!:* tolls ur how c-hj.s destructive tendency
-,!-\r proh-atOy avoided by the one ion ; quarry ron of flint
i fie r -o fa c e.v-J -j n y o hie cie to r,,. in a t i c u : fire was bn 1.11
upon the r;a'f u-e of the filoL body-, such port-ions o'
the ; arm star s as rere de cured for use belay protect!
fro-:, the action of the hear by leyera of mo lot clay
( Heir: e s 19-19 y04 ).
At the rovr.cu.life or. arries near hot Syriaus, .rkonasa,,
\'h i c o ? r e o o s cb 1 y ss e :* t o n r: I ve a s t h o c e o f PJ i.¡ 11 id d l s C}' 1 o i
Hoir.i: :> (1 v 1 : 193) obsc :: ro0 soo.o u.: o of 1 : re in th.; qr.Try5 nc;
opera Ho; -s..
K11 i-_ ClV->0:* ; p) sc r Ibe s ari eup-ari;r.ort corb vouo£
by hill inn 0 Kills ah 1id.t hi due ubica rr-q eme sous or.hi
or i f:: a v sp of fire in qu a r-ry irs 3 opera.z ion a :
i!, hora v:>.l tbo buc. o f f1int urccv ruI n0 1
abura '00 of dry vueocl at lure. The* fire was 1:1 oiled,
and vac :>q.t b1 .or bu; 1 or two sours., picaroj.r.u an in-
toaos* :0a or. oh- ondcrlyinr .*: urfvf t;he hi5n;,,
Th f J n: trv.:: f, 1 rt: oiov ? 1 or d t -:o l- : . ; u, s 0 " c o 1 d
v: a ; 0 r e r o ; h*.u on t he 3 v. r f r.c e. 1 f ah i y r-:.. ;. c j f *j
the fjhot to br? .: in i^r:;e hluce':t ecu, ;Lt uerohy
cnr.nd e:: -.= c: e i : 0 r :11 _,ic;- _ c v i:: d o p ch oi
Perh ip^ ; X f 1 pc a f.ft c -1 hho c c'.:.sio ! t'-i
oay e i 1 r -0 jr . n t t,.at f i re 0 0. direct cut
:i.n q.::..; } a.;; o r 1 h?!- :u\ v. :.er' 1 a >:j nc c i: bet ice 1
T:o fr.11 o'.:in onecof Indior r cpcr- i 1..va in the
fc hi ;11 Hill- 0i... n ;>y ?. v i i i 0 in t ero o t ir- y b o. o cuse i t hi nt 3
of V.o poo rifle voo of fire v-o fracturo :v--oto in a las-nner
e i v.\ i 1 :r t o ': r i n h v '3 o a P l r v- : o c r, do s r i j ¡3. i ji f h c p r c v : c
cetcpcry:


'j.;he exporiae ;V descri¡>t*d ir: 1 -.' goo re o<:ji¡. -
c!.u*jte tr.kss i 1£.ce in sicrccrystal j j :? rock by.: vycr ;:? o1 bj... i ¡ n ake s t n ear ier o II a:: c f e syc c i a ii ;> v; o yos t.ro .¡Vi a he s
Tf a y cl\ a c b a:< vy £ doc c-f.Cur t h e r y i 11 o r y r op o c 0 t o cl : r . i v
at i, :h y. t t e r:;; : e 3 -a t u e o Ir: rat :i c r. t r b c o i.)o c e and ; .i: : t a r t h o
ph?j r? i o a 1 ov c?; onic a 1 c I' < r1 a t c ¡ c:: c- j. ;ar V i -n.
Via ene ver coup arise;.-: nade a loaVoc l.:
a na vm he ate V c on uro 1 ?., t h e r j.i. .a.: j ?. . : -o o i. i;= r. d i \ ' c t h o
n ai iC; c ore Vr? at ter a v- v: n :r. ad-; t o a e : .: t ..l! ;r.r f . :: v .
fo £ j. i ; i. a X U 31 C/r 3 o r- o tlvi* I' he V: V ? 0o >. c-b 10 0. a p :' b i *: X i :
t o oh t air tu o o an pi e- s fro r av. p ::o o:: r. a L o i y t..: c. n *ro a o .f
Va core .or. o.ce to:* l ji j 1 di V locc> d c c >o; io;< ir \ : roo ,
Lao :_ a a v r. ? 11 y o d.? r u r o c o te;: Vn <. n 3.y 1 a;,; IX: -: :
;r.£rCi tbt:.: i.ur.r..tX.V;. v';-o T,;a>t- Xarovpoo- !; t-Vo ac.-c--
r< I go r t:?. ,*r o; ¡ c a r. a a t c
. OrL i o aX tan> r aturo >; c \:l a el - V %.. *.> :>? r;o j gi g '- 0
s p. >5?0 .;* "G* cU ^Ipo yAc i:* in:;o:*.::vGr tl'.o ratcriajf bo: r-
he V ed : /o r-. . i h ! t. o ;a ' o 10 J e_-f '- v . tg i o : o
tei \ a tu i-2 u : x; i i 1- :. !; £ : t:. : y be1 o v -i
r o a !' J *j t> a .or: t '' - <. e i1 f:-' o e > r -g j
raj 'j le.v i root'. ; ; o .-. .v oou. V i Voio:,
V-. Pay * r-.lt. o \ r t io: ::: b r > te n a.! c 1' o i ? ¡
br : ;r' * :*-.. g' ' r '' :'/" bi" ir>
y,o1: 'err.t:;:ro ur t !. V . t¡ ,,f,.'. y Li' o '. 0


80
unheated
heated
Figure 17.Surface Topography of Unheated
and Heated Johnson Lake Chert Samples as Viewed
by the Scanning Electron Microscope (Scale: 1 inch
254,000 ).


65
siliceous materials are heated to temperatures of 400C-
500C for sustained periods and removed while hot, certain
stresses occur which cause a reduction of strength when
compared to the unheated controls. The three unheated
varieties withstood forces ranging from 44,000 to 55*000 psi
(rounded figures) while the heated samples of the same mate
rials ranged from 25,000 to 52,000 psi. This represents
approximately a 40% reduction of strength in the heated
samples. On the other hand, when the heated samples were
allowed to cool in the oven, as shown in Table 9 there
was an increase in strength amounting to approximately
25% for obsidian and 40% for the High Springs chert.
Cohering the material without the introduction of stresses
allowed the heated samples to resist failure for a longer
time than unheated counterparts or heated specimens that
had been stressed by sudden subjection to a cool environ
ment.
No comparison should be made between the pounds of
pressure per square inch recorded in Tables 8 and 9. The
experiments were conducted several months apart, the equip
ment was operated by different individuals, and the rate of
load was not observed for the samples removed from the hot
oven and their controls. The rate of load for the Table 9
samples was approximately 20,000 pounds per minute. In
addition, and most importantly, the samples were different.
The obsidian samples were from different locations and
therefore probably of different ages and depositional
situations. The reader is reminded that man has classified


BIBLIGGRA
AoC/L: itOi.. -M
lOGl sui3.1 o; v in Archae oosle al in terj-rs o at ion
Southwestti Journal of An thro o o or"-. Yo] 1 / v
pp 17-25. ihlbuquer queV
SEAKALAAIidd, I.0UI3 I.
i9-14- Differential Thermal Analysis of Quart?;.' LAlted
States Dapartient of the Interior, Bnvogu of
iline3; Sooort of X vc-s t i?;at.107-s, irc. 3'f/oC,
Vashington.
OIDGS j FRANCOIS
10b8 The Old Stone Age. KcGrav;~II:¡1 1 Boo1-; Co. New
To fin
BUAAhOU, P. A.
1909 Aboriginal Remains In the Kiddle Che ttyhocchac
Valley of Alabama and Georgia. American.
An t h nop clog 1 s, t. V o 1. 11, No. , op. 1 tlG ~ c)t .
l.enoaster, Pennsylvania.
COOK'-;, 0.
19^9
GTiTiE
Geol ogj o f 71 orid.a j'l crid a G0 c 1 og ic a 1 Surve; s
Geologic-el 3n?i 3 ec: r,, fto. 29. Ta 11 aliassav .
c:us
l-G-'l-
.00?; S, AND B. ROBERT BUTLIH
Botes on Experiments in Flint Si:ape:no; I. Heat
Treatments 01 Silica Kirs erais. Tebisoa, Vol V,
?'o, 1 ru<. 1-G. 1 oe"itollo, Idaso*
!v: ,j- ir ; Cl a:: c i ic 5 : n a:- a I:de; irope at 1s f c:,
Intco t 2a0::. Tael a Ap: gl_ __deport, I-o. Ai'V.L- TA-GS-11 ,
Un iv 3 ns i l j o f iTTifr'o i s 'lid) a: ; a .
1 -1*
i S-: C a l3 n i: Vo r V. in; Tc r- i;pso s o f f¡ Ar :o r :i c : n 1 n d:: an s :
Ao Expor*iii.enta 1 .An>.\ the Clio J-li tor ion I Gog 1 'A
_t rib 1 i-j l^-Gb Tho j.Ysoiblo Cultural f il i:. ti y;, o Ai ? nt Lis::
C sc lias, Oh i c __ .re; 1& u 1 o i c a_A ; a A .A i c "*
cui Atorh/i 7ol,'d9V "v9"GoiV::.a>h
92


68
e3q>eriment were as follows The imheated Ocala chert with
stood forces averaging 2700 psi while the heated Ocala chert
withstood forces averaging 1500 psie This represents a re
duction in force by 45% needed to break the material The
point load tensile strength was computed from the following
empirical expression given by Reichmuth (1963):
T = 96^ where
T = tensile strength
F = total failure load in pounds
D = core diameter in inches
The information to be gained from point tensile
tests was considered pertinent to this investigation because
the amount of force used to induce failure of the material
by point tensile stress is essentially the same as the
strength needed to induce fracture when manufacturing lithic
tools from siliceous materials by either percussion or
pressure methods. Therefore, extensive experiments were
set up to test the point tensile strength of differing
materials in various ways.
1. Four samples of obsidian, High Springs chert,
and Johnson Lake chert were tested as follows and allowed
to cool in the oven:
1 sample of each used as controls
1 sample of each heated to 300C for 24 hours
1 sample of each heated to 350G for 24 hours
1 sample of each heated to 400C for 24 hours
2. Two samples of obsidian and of Johnson Lake
chert (from same core as Johnson Lake chert used above)


Weight Loss (%)
1.86%
1.00
ro
oo
1.55%
Figure 2.Weight Loss upon Heating of Cherts from Various Locations in
Florida (note the rapid increase beginning around 350C).




LITERATURE REVIEW
Following Crabtree and Butler's (1964) article,
archaeologists began to look for indications of alteration
by heat of materials used in making chipped stone implements.
It now appears that this phenomenon is very widespread.
Despite the fact that most early explorers, colonists, traders
missionaries, and adventurers were very poor ethnologists,
it seemed surprising that this technique had not been ob
served and described. American Indians, as well as other
primitive peoples around the world, readily perceived the
advantages of iron tools which were introduced to them through
European contact. They willingly put aside nearly two million
years of stoneworking technology, often within a single genera
tion. Unfortunately, very little attention was devoted to
the material or practical aspects of Indian life until the
middle of the nineteenth century. It wasn't until many
aboriginal practices had been discontinued that a rapid
attempt to record these practices was undertaken. In some
cases, this attempt came too late. For obvious reasons,
therefore, it was necessary to turn to nineteenth century
sources almost entirely. Thus, literature, which in most
fields of endeavor has been laid to rest, was reviewed in
an attempt to shed some light on a recent observation of
man's past behavioral patterns.
5


31
Table 4 for the results of this experiment. It was hoped
that this experiment, though simple, might prove to be a
reliable and inexpensive method to be employed by archaeol
ogists to determine if chipped stone remains had been therm
ally altered. This will be discussed further under the
heading Archaeological Application, but although there is a
fairly consistent difference in weight lost on an intra
sample level, on an intersample level there is overlap.
Therefore, even if an investigator knew a great deal about
the rock he was recovering (that is, source, composition,
etc.), he would have to be careful in assigning too much
importance to weight loss. This experiment also indicates
that the weight loss at 100C is probably not too indicative
since it would fluctuate greatly depending on how damp con
ditions were prior to heating. It has been demonstrated
that an appreciable change in weight occurs if the samples
are left at room temperature after being removed from a
moist environment (see Table 3).
Materials from the field which were thought to have
been thermally altered since they were quite lustrous and
many exhibited a pinkish cast were heated in order to com
pare weight losses with other specimens that were known not
to have been previously heated. The results are given in
Table 5 II this table is compared with Table 2, it is
apparent that there is no significant difference in the
amount of moisture given off between the materials that had
been suspected of being previously heated and those which
were being heated for the first time. The results of this


34
comparison plus the data derived from soaking samples for
a month in a moist sand bath indicate that it is not possible
to use weight gain or loss as a reliable criterion in deter
mining if archaeological specimens had been subjected to
heat
Decrepitation and Explosion
It was no mystery to primitive man that fire could
be destructive to rock (see Literature Review), but this
investigation has attempted to demonstrate that when
siliceous rock materials are cautiously subjected to heat,
an alteration occurs which conferred an advantage to pre
historic man In the manufacture of his chipped stone imple
ments. Man had many thousands of years to discover this
fact and to perfect the technique. Since the use of fire
and the use of stone were two of the earliest and most
important items in the inventory of a physically and cul
turally evolving creature, it should come as no surprise
that he gradually acquired an intimate knowledge of their
attributes. The observations to be discussed below are
probably much like those made long ago.
The materials involved in these experiments were all
Florida cherts. Reactions might occur at different tempera
tures, or not at all, if other rock types were used. Suf
ficient samples of non-Florida materials were not available
for experimentation. These should be tested eventually be
cause the results would certainly be enlightening.
Webster8s New World Dictionary of the American
Language (1970) defines decrepitate: "to roast or calcine


Weight Loss (%)
29
Temperature (G)
Figure J.Weight Loss of Samples of Florida Chert
Illustrating the Typical Pattern Observed for All Florida
Specimens Tested Throughout a Two-Year Period (Obsidian,
Arkansas Xovaculite, and English Flint did not follow this
pattern).


72
Figure 14.X-Ray Diffraction iattern Illustrating
that No Change Occurs in the Crystal Lattice when Florida
Cherts Are Subjected to Critical Temperatures.


79
electron beam; the technique does not eliminate or create
any additional surface features" (Krinsley and Margolis
1968: 458). Heated and unheated samples included silicified
coral, Ocala chert, High Springs chert, and fine and coarse
grained Johnson Lake chert. The specimens were placed in
a Cambridge Stereoscan electron microscope housed in the
Department of Metallurgy on the University of Florida Campus.
The entire fractured surface of each of these specimens was
scanned. Figures 17 and 18 show the typical surface topog
raphy, dramatically illustrating the changes which occur
when cherts are heated. Figure 17 is of Johnson Lake
chert (1000X); Figure 18 is of silicified coral (12,200X).
In the unheated specimens, the individual grains are seen
looking like so many bread crumbs. Some fracturing has
occurred through the individual grains but more frequently
the fracture goes around the grains. In the heated speci
mens, the fractures pass through most of the individual
grains; that is, the individual grains are actually split,
and the fractures continue on passing through the inter
stitial areas which are now more firmly cemented. In other
words, when fracture occurs it alternately splits and
passes through succeeding crystals and intercrystal areas
in its path until it terminates. This accounts for the
smooth surface in the heated specimens.


TABLE 6
HEAT SOAKING EXPERIMENT CONDUCTED TO ASCERTAIN LENGTH OF
TIME NECESSARY TO EFFECT THERMAL ALTERATION8-
Sample
Hours
at 350C
Hours
at 400
0
O
No.
2
4
6
8
10
12
2
4
6
8
10
12
40
+
+*
++
++
+
+
++
+++
+++
+++
50
+
+
++
++
++
+++
+
++
+++
+++
+++
+++
60
++
4*4*
+++
+++
+++
++-4-
+++
+++
+++
+++
+++
+++
PO
aIf the space is left blank no change in vitreousness or flaking ease
has occurred; + means change is slight; ++ change is pronounced; +++ change is
complete. There was only occasionally noted a difference with regard to change
and sample size. The smaller samples weighed approximately 3-8 grams; the
larger samples weighed 50-80 grams. More attention was paid to thickness in
selecting the sample than weight. Extreme crepitation occurred in the samples
heated this rapidly to 400C and in this regard, the larger samples were more
involved than the smaller samples.


?1
strength which occurs v/hcn see cinara, are reiueve ir,.. ?di; ..lu
fre the hot oven is due to stresses resulting when the Satc-
rir.l is exposed too rapidly to a cool cryironnenh.
X-3ay Diffraction Pattern
twenty-six x~ray dilTraction patterns viere run on.
J.J dif ioj-w*L feampiijfe of Looted and imheated cherts. Kn ooa-
.-iistent differences could be detected iudicatirr that- no
change in the crystal lattice occurs (see figure Id). S.e
slight difference oovm is well within toe ¡pesia of axpsri-
xentei error. If the crystals wore coarser, the peak 'would
bo higher; if the crystals were finer, the l*aid would a*;
i oner.
differential. .Thermal.
The method of studying materials by differential
ther;.,.-J. analysis consists of beating a small, finely ground
sample at a constant and rapid rate, and recording by suit
able moons the endothermic and exothermic, effects. A dif
ferent;, a j thermocouple is used to detect these effects.
Ono of i ic t; or:.cccup 1 e unctions is p 3 ycc6 :ln 'the sample
boirr. stiido '! and tro other is sat in a thc/: o 1 2- inex t
substance that is underreirg the same heat treatment as
f he e r. hile (:' o rk e 1 h ' rao r 19 > '0 Th e e Ice trie c v ;-v ant gene r-
t c d b y t h jr c1 i f f e re n t i a 1 t fro r :c c c u; < 1 j i ?, a 1 i f i cl an cl
recorded. ur.dochcr.iic peeks result if the smele is 1r Mug
on energ.
dai.iples v.ere prepare! of iu;: e pu.rts, me o;:al,
' a v_, he ~ t.'.i John.:or 1. I e c "r 'Ti.fr J. .... o
l e c


91
A review of available literature has uncovered
numerous accounts of the use of fire as an aid in the chip
ping processat least enough to warrant the conclusion that
primitive peoples knew that fire was capable of producing a
desirable change in flint materials
3. The problem of recommending an easy test to deter
mine if materials from archaeological sites have been inten
tionally altered has not been very rewarding. Test after
test has not suggested any really reliable criteria. From
an examination of a representative sample of flaking debris,
however, an investigator should find a number of specimens
exhibiting a relict dull area surrounded by areas of extreme
vitreousness. This situation strongly suggests that the
dull area, has not been flaked subsequent to heating whereas
the vitreous areas have been.
The evidence presented in this report leads to the
conclusion that the manufacture of chipped stone implements
is easier to execute if lithic materials are first cautiously
subjected to critical temperatures (350C-400C for Florida
cherts) for sustained periods (12-24 hours hut varying with
sample size). After nearly two million years of experimenta
tion with fire and stone, it should come as no surprise to
find that primitive peoples were well aware of the advantages
of thermal alteration.
Artifacts have always been the archaeologist's best
friend. A recognition of textural changes occurring when
siliceous materials are thermally altered provides knowledge
relating to lithic technology and primitive man's behavioral
patterns, thus establishing a new dimension to archaeological
interpretation.


This dissertation was submitted to the Dean of the College
of Arts and Sciences and to the Graduate Council, and was
accepted as a partial fulfillment of the requirements for
the degree of Doctor of Philosophy.
March, 1971


38
Two samples that had been heated to 350C for
24 hours were removed from the oven with tongs while hot
(still 350C); the tongs were warmed on the side of the
oven before touching the hot stone One of these samples
snapped in half with a very loud sound (room temperature
was about 75C). Cold water (tap water) was dripped along
the edge of the samples with a dental syringe to see if
they would flakethey did not! (See Literature Review for
accounts describing this alleged phenomenon.) The samples
were then placed directly under the tap and cold water
allowed to flow over the entire sample. This resulted in
an audible hissing sound and a crazing of the material. The
same procedure was followed with two samples that had been
left at 400C for an additional 6 hours. Crazing occurred
and subsequent attempts to flake the material caused it to
crumble. It was impossible to pressure flake this mate
rial because the flakes could not be removed in a pre
dictable way. The specimen literally fell apart (see
Figure 5)
Failure on quenching was shown by irregular cracks
differing in appearance from the smooth conchoidal
fractures . (Pressler and Shearer 1926: 308).
Other experiments were conducted to test the
significance of the crackling sound which occurred when
specimens were removed immediately from a hot oven. These
experiments will be discussed at the end of this section
and in those dealing with Petrographic Analysis and Strength
Tests.


6
Iwiy excellent accounts er. t of oj. ipar 1 riere
pcrieir,,; techniques. In addition, numerous experimental
studies 2miv3 bo-on conductos and reported upon ghio'b. describo
tibe -stpp try step Hsruiactu; o of tools by lloco psrcu. ; ion,
indirect percussion, pressure, end various coi si nations cf
these Eethods. Those techniques constituted the rayon
processes employed in shaping and finishihrv stone tools,
She author does not wish to pive the inuroesion that it nan
alv&ys necessary to ther-Bully alter litliic Eatorinis.. tore
Ketorials probably needed no alteration. Mor is it felt
that fire was used in shaping. But it is; thought that fire
often played an .important role in Satiny the techante?!
processes less difficult dur-iny soma stars cf Hitnufacturc
prior* to final retouch..
Holmes (1919) compiled a sunasry volur-e entitle..!
Aboriginal American !rtj.gulties, the sources for v.-lich are
njiirXy all pro-t;;eutieth century a a -perusal of tho fclbliog-
B'-vrh-J indcete a. Ills booh Sorvei *.> t nnc'innuocn-d tv the
past Mcj Chapter XXX? is entitled "lire fracture Process"
and contains a uunohe. r cl useful refer;.doer those of v.-hich
v.-orc- available, in turn. Jed to others. hio' of these early
publications rare not avc.ilabie. 'her;: tie the fact that -'-
elote cover eye v. :: iKit possibie, it aeon Vacant apparent
that nan's use of fire lx- conreeti-r.-n oath lie chipped stone
teol-v.akiha; technojryy fell into three sain cater cries;
(t ) oaa; O' flr.-s to fixe as pa aid in its oMypiny
jv'oves:.. (ip; o p fire in qaarryi.n:; opexuP lono (J) cache;...


77
unheatcd
heated
Figure 16.Petrographic Sections
Showing No Detectable Change in Heated vs
Vnheated Florida Chert (Scale: 1 inch =
1,500,000 A).


* principle -f surface ch ..lot:' . /m a
crystal c^rriGt 03" high.1 j 3 olari;.. / cnior;.; of .1 arL:0
r j. z p, i; e i. h a r 1 s ro a 11, tv; hly c : T: : c a ti c m ,
then the : u'jo .'111 1)0 pur.hoc", to : >n-.'face o* the
ory s 1' n 3 c A iV c*. v01:3 wII': b< re0ored, f hue in a
uio'-'-oory.-ya.l of snorts oxygen ions ; a."--dominate at the
r.urieicc j while ¡.'a sill'.'.on ions ano depressed. It is
believed that each tul of ruarte toen, has a
n0go tive 1 y cl;ar go d "ekir and e 1 l/ct-:1 vaj.;; rep>r 1 a
adjacent: rand only oriented uric roe :lo f'actin''
nr oh. ;h 3. y t alee s ul ac e b e t w 0 on t) to r 01 ;yh c 1 r J b 1 00 k.s
because of the surface remisin forces (Ad 1; sod
'.-.hover i?07-6).
VI _ the roots arc sub-jeered to critic..-. I t encratenos tv
may b r- a c. h 0 a p:e ys1 t he posit i on c f cry gen an d c 31 i 0 on 1 on s
as described above* If the ions become too excited v/hon
ta. = -p0roLurc is a.0 1 iecl ra.fl 1 y v ex; 10sic.n a ey taka 1; 1 n0e c
Th i s i -ay a 3. s o c x: .1 a in the c 3. i ck i.r g so: aid: \ 1 i c h o 0 s ur and
often rc..Ta_i t in exfoliation when the material is rap id I j
c o o .10 d Pe rh apa the reason these clicking so unde aro *;: i
beard when the mate eial is remove cl after a susto irc-d r: erica
is because the process is completed and no further uhnoge is
taking place.
7a 51 u re v:u a a c c omn uni e d 1 y pe culi a r c 1 i c k 3, 1 : L11 c a c
"clicks" were heard early 121 the cooling period ora
rot or iurica the heating period, when the rate of
t a =r erp f ure chan- a ;as 1 ov*er when tho cup 3 1 ?e re
be e t e d t- 0 a si ip, r. t X ? high or be: v -or aturo no hi;:} 10 r
; a 2 -0 e71ap e 0 f fa :> 1 u tes v;aor a:: 1 vc-d (J.:re ¡3 s 1 e r and
b h; 0 e ri J ¡?7>: I h 7 ) ,
a : ; r 3. fa- t a a ; l or be a t c d t o 1 c f r. j a e a sie r t o f 1
fl.athI e j t at; pf?0*C f 02:* p¡ olrnjvod pr*vi oda ( s^ 1 Fi7, ,l.
A - j u 1; r j o f a up 1 e rj we i-e 1 e ac 1 t o V ';CC *; u b. j e :;v e t cb ipp ir
o l fb 1-sc s. ocimen. did not re v- .1 .1 ; vj fv,v ;1'cr ci. v ; .. e 11r.
owe v c :. p in t t l .; r; i i e s 11 a 'pi. c e ¡. t l. t <3 b o d .. ene i j -. 11. 1
d o 2101 up. or L- thi e oh r e rv a . .1 c u r; in c u f 1 a r c i s in c r - r. s e d
r t ron g t h .1 o ~ ?. i t h i r r^. :: . *. ¡u--; - A1' yo tv r? r p , t J-- v r \ 1


ACKNOWLEDGMENTS
This study could not have been, undertaken or suc
cessfully completed without the cooperation of many people
with varying scientific backgrounds who contributed their
knowledge, time, and equipment. This type of interdisci-
piinary approach is increasingly important as specializa
tion becomes a necessity in an extremely complex world.
The author wishes to express appreciation to the
Department of Metallurgy for making it possible to use the
Scanning Electron Microscope; the Civil Engineering Depart
ment for the use of their equipment and for assisting with
the rock mechanics tests; the Soils Department for the use
of their ovens, for assisting with differential thermal
analysis, and for conducting the atomic spectrophometer
analysis; the Geology Department for assisting with petro
graphic analysis, determination of surface area and porosity
of Florida cherts, and for permitting extended use of their
oven; the members of my Supervisory Committee, especially
Dp0 Charles H. Fairbanks, for suggesting and approving of
these investigations and for editorial assistance.
There are always special people without whose sup
port. graduate students might find completion of research
projects overwhelming or impossible This author is very
grateful tos Mr Don Crabtree of Kimberley, Idaho, whose
ii


44
Figure 6.Vitreousness Occurring when
Florida Cherts Are Heated and Subsequently Flaked.
Top: Specimens were Heated Slowly to 350C, Left
for 24 Hours, and Cooled in the Oven. Bottom:
Specimen was Heated Slowly to 500C, Left for 5 Hours,
and Removed Immediately from the Hot Oven (note relict
dull area that has not been flaked after heating).


40
Vitreousness
To vitrify is to convert into, or cause to resemble,
glass or a glassy substance by heat and fusion. The more
vitreous an object is, the more it has the luster of broken
glass. In order for a cryptocrystalline rock to be con
verted into an amorphous, noncrystalline structure, it is
necessary to subject it to temperatures of ca 1400=1700C
(approximately 3000F). Aboriginal peoples in the state
of Florida could not achieve or maintain temperatures this
high. This fact is known by the quality of the pottery
remains which indicates that pottery was fired at a much
lower temperatureprobably not over 550C (ca 1000F).
Since the practice of altering lithic materials seems to
have occurred on preceramic levels in Florida, it could
not be assumed that earlier inhabitants were capable of
producing temperatures higher than their descendants.
Besides, from petrographic analyses, which will be described
later, it has been demonstrated that the size of the crypto-
crystals does not change even though vitreous luster occurs
after heating
Florida cherts are characteristically nonlustrous
and coarse grained except for an area directly under the
cortex which may be as thin as 1/8 inch or as thick as
several inches, this latter being exceptional. Occasion
ally, however, the chert is slablike and ledgy, not exceeding
an inch or two in thickness. When chart like this is found,
the fine grained area generally extends from cortex to


21
Figure 1.Areal Distribution of Outcrops Probably
Containing Chert in Peninsular Florida (adapted from Cook
1945, Plate 1; Brooks, unpublished geologic map of Florida).


32
rAr'L.-, e
HKATj.i¡r Avi ...All. x Ov ''uUj.'.L-'
ibated :: in-ls j o. lot* e;,3 nt.:
; x.- ... x.
hJ'siC- i-OA (... ; KCT\.
Vi*; Loss
ft :r hr
Additional 't loos after
Sample
at lC.C
24 hr at 550G
(a
OO
(>)
Ah
,42
.7 8
, 16
Ah
. '0
, 37
.18
As
- %
.79
7.0
Sil
J ,08
.*0
.03
Sil
i O'
.51
.05
Es
.89
* .15
Fh
. 50
.4?
.03
Fh
,28
1G
,1V
i's
.51
57
.2?
lh
.5.5
* 7'-
,ce
:-¡h
1.0?
.55
- 53
lis
1,00
. 7 J
.25
Jik
.53
. 05
f'.h
,57
.'+5
,0+1-
Es
.55
,83
5ii
.55
0+7
.03
'fh
.5
.10
Vi j .8?
77
.35
3. cal at o <5 fr*veifht o4 3ai.r.les 2;l- hovr;, after
roi'vvj f.eo.: :.oijt snnJ bato.
0CeX;-'-4t at ] *Vw-:i ,-\.ii;;hf o v,n oer -iys after
rc-LiOVi: free : is ¡; :: ni Vr.1i,
"iriil-: tlic-xa appear o fcw La a i¡;h';, y.;.f unreliable
teiicVmey .Cor i-c v^i^bc loo i fe V. ato- . C 1CX,00 for the
VJOCofcJ rooco se ral : s ,, too va:. 1\\: icr?: ;..s: quite
c an o 5 .: y o : f f o- r ti1 o u. r 1 \ o o.. t -..! s o o 'o i 1 o.: 1 o o bec. c > 3 0 O; :j
1 :.o-io f 7o-oo o there in ov'-iO oq in /ercujxf-v- eo be-
Curen lo : 1 f* m:d ro ;.'f clsyer. .5r:'. rn Iba r:r. v.qlc irvoj ved
tMo j-'ftho'ij vhi.3 : fc within rp-T/lc. r, eoij.Vj not be
rooc: oo or -rctc ol r. ; -.1 . r ; no: o; tren if t ho investi~
iator bod :: 'vofoo.-! hvovilthh-- c-f' lbe raooriols i;.itK which
he roo fe ai :h if the Xu .ulbs oc/' torn- oiv:.


?3
from Cool' vhose grain size is interine date of the Jiree
s8mplcs. Host significan11y, the Eocene chort fro Oca] a
thet ;; 'jd b in beetec. showd a a a rhe.cl reduc'c-i :ln the
a 2 .
gr m i j r s v r face arc- a: 1, 9(-j " /g c ora a r e d t o ;'r 56 h / a
for i e a iu i ho a t c d count? rp art* Th i y :c e;; r e <: c - r.r-ji rcxi n a t c 1 j
o. 60;'.', r e duo t :* c:..i i:. th c y ranul a r s urf a o u r o a of the heated
o he r i- v i1 he re i s n o a: t i on bu t t ha t t he icic roc r-y s t al -
j J: £ surface area has !> on reduced in the heated specimen.
hi'! ;i s v! a e d u ; t o the ro duct ion of the in t u r gr an ul ar o r
radii. In other norda, porosity had boon decreased duo to
fusion cp intergrowth of the grains*
A computer printout shovn.d. the size of the cove
:jace di a tributi on and aurf c o are a a j.str xb o t ion r ">I a t ive
to pc .vc on1 a. _;e of o c currenc e The p 1 o L for Oc al a unhe a ted
c iC.rt shov/cd tha n ir,*>to s i zr o f the ori gina. 1 p ere s : 27,81/
of the pores wore 2 bp. or smaller in size whereas about .1-T/
vore 570.8p
Sc anr< nr 51 c c t r on Horoscope
Tho scanning e] ectron r;.ioroseope (0 j') is used to
study uerfaoe morphology (hrius.l -p- end huigolis 1963).
Small fichus not exceeding 3/3 >: 1/2 inch were pressed
fro¡x uv h o a t o an d ho atod c he r t s. The sar;irlos v with ace tone end irounte0. vith Scotch tape on an SEM speci -
men plug, Three .four spec3 v.rs were mounted or each
plus* The freshly fractured surfaces wero expo-a-d for
s c an n n g, Tla e r : c i;:¡ r. n c i aa re t h-j n c o a t o d v i t h r;o 1 ci 11 in
ordo.* to ruho th? surfaces o better con 'uctor for the


BIOGRAPHICAL SKETCH
Barbara Ann Purdy was born August 23, 1927 at San
Diego? California. In June, 194-5$ she was graduated from
Herbert Hoover High School. In June, 1948, she received
the degree of Bachelor of Arts with a major in Zoology from
San Diego State College. In 1949, she was employed at
Scripps Institution of Oceanography at La Jolla, California
in the Department of Marine Microbiology. From 1949 to
1953, she was employed in various departments on the campus
of the University of California at Davis. From I960 to
1965 and intermittently to 1967, she typed theses and served
as Thesis Editor at Washington State University, Pullman,
Washington. In the fall of 1964, she enrolled in the
Department of Anthropology at Washington State University.
From 1965 to 1967, she was a Research Assistant and received
the Master of Arts degree in 1967. In 1967, she enrolled in
the Department of Anthropology at the University of Florida
in order to pursue work leading to the degree of Doctor of
Philosophy. In July, 1969, she attended a four-week flint
working session at Shoshone Falls, Idaho sponsored by Idaho
State University with funds granted by the National Science
Foundation. She was a teaching assistant from 1968 to 1970
in the Department of Anthropology and taught American
Institutions in the University College at the University
96


S3
TABLES
iffiBL-. e? C0I6 ..-l-civs sills .mcn
HIATOS SLSClS.IAi ACC SUSuSCT.S AC A COOL
ERVJ30KK:|t L'HILK SOIL].: iluT
Sample
Urhostal
Control
(psi )
=, ~r'::
Hoat od
(psi)
Strerg-iH
Lone
(5
Obsidicjt X
50,IOC
30,000
4-0
Sil ici.tied
coral
43,900
25,000
¡3
Co alii chert-
52,994
31,720
AO
TABL2 9
HI...,I Li -J? CCLii.C j" V.3 TAIj; 10313 ..'SSL :M,
SIECLMIIS Alii: ALLO'./SD TC COOL IS Till OVSi.
'¡x¡ ala
Unbeaten
Control
(psi)
Hoate d
(psi)
Obsj 4 i 0
31.100
59,600
Hi;*]' 6prj.iijrf
23*3 CO
42,200
Increase iS'
StrdA^uh'
( )
25
/JO


conclusion that fire was used sometimes in conjunction with
lithic technology.
An examination of archaeological chipping debris
revealed that a portion of this debitage had been intention
ally flaked after heating. The flaked surfaces are lustrous
and differ in this respect from outcrop samples of the same
materials. The flakes also have bulbs of percussion in
dicating that impact has taken place. Bulbs of percussion
are not present when rocks explode from thermal stresses
though the conchoidal fracture typical of flint materials
is evident.
3. To recommend a technique which might be employed
by archaeologists to determine whether the chipped stone
remains recovered from sites had been thermally altered.
No practical standardized test was discovered. However,
from an examination of a representative sample of flaking
debris, an investigator should find a number of specimens
exhibiting a relict dull area surrounded by areas of high
luster. This situation strongly suggests that the dull
area has not been flaked subsequent to heating, whereas
the vitreous area has been flaked.
Temperatures of 350C-400C are sufficient to alter
Florida cherts but x-ray diffraction patterns demonstrated
that no change in the crystal lattice occurs. This was
borne out by petrographic analysis which showed no change
in the shape, size, or orientation of the microcrystals.
The alteration is due, at these low temperatures, to the
presence of impurities in the rock serving as fluxes to
ix


97
of Florida during the fall quarter, 1970 and the winter
quarter, 1971.
Barbara Ann Purdy is married to Laurence Henry Purdy
and is the mother of four children. She is a member of the
American Anthropological Association and the Society for
American Archaeology.


95
SCHMALZ, ROBERT F.
I960 Flint and the Patination of Flint Artifacts. The
Prehistoric Society, No. 3 PP. 44-9. London.
SCHUMACHER, PAUL
1877 Methods of Making Stone Weapons. Bulletin of the
U.S. Geologic and Geographic Survey of the
Territories, Yol. 3, pp. 547-9. Washington.
SHEPARD, EDWIN M.
1877 Deposit of Arrow-Heads near Fishkill, N.Y.
Annual Report of the Smithsonian Institution,
for the year 1876, pp. 307-8. Washington.
SMITH, CHARLES M.
1885 A Sketch of Flint Ridge, Licking County, Ohio.
Annual Report of the Smithsonian Institution,
for theyear 1884, pp. 855-72. Washington.
TULLIS, JAN
1970 Quartz: Preferred Orientation in Rocks Produced
by Dauphine Twinning. Science, Vol. 168, pp. 1342-4.
Washington.
WALLACE, ERNEST AND E. ADAMSON HOEBEL
1952 The Comanches: Lords of the South Plains.
University of Oklahoma Press, Norman.
WENK, H. R., D. W. BAKER, AND D. T. GRIGGS
1967 X-Ray Fabric Analysis of Hot-Worked and Annealed
Flint. Science, Vol. 157 pp. 1447-9. Washington.
WILSON, THOMAS
1897 Arrowpoints, Spearheads, Knives of Prehistoric
Times. Annual Report of the Smithsonian Institution,
U.S. National Museum, part 2, pp. 811-988. ~~
Washington.


66
er-:porira ont we i o as foilo\*g The .mhoatu>1 -cal:, c - r t ?
stood forces uveraping 2700 psi while the roated Ocal." ch--.
withe toed forces c-.ve raving 1:300 psi- Thr l represents a re
di! e. t a r> i:o f oroe h;r 0 3 /. h aod 3 cl to ere dc th£ r.:.i;01 i a 1 The
point 10-'.d tensile stren^bb vis cc imputed fro,-.; the follot.ijg
cu-j. -irioal c xpre *c i: gi vej 1 '::.c i ch 1 t h (1 $-6) :
T -- 96J"o where
IT'
T = tensile strength
!F = o o t a 1 f a'' lore .lor d :u. p c ivo 0
1) coie diameter in inches
The inforxstion to he sained fioiri point tensile
teats was considered pertinent to this investigation because
the amount of force used to induce failure of the nuterial
h.y p g in b tensile stress i s e r a c n:, ia 11 .y t Us e r. an c s t h0
si, re rr.ih reeded to induce fracture 1 ¡hen ranuf sc tur in,; 11 chic
tools fror. siliceous materials bp either percussion or
P sc unothocls. Therefore extensive expri:en tr> mc:re
s f 1: u;:' o t e 31 t he p o i n t t e n 0 i 1 o s t r ear t b o f d i 1 f e rir 1 _;
x a ~ e *1 .1 1:1 o j; 1 vor 1 cos v:r;\ s,
1* four sarcpl.es of obsidian, hiph ip r-imps chert,
& nd J ' 1 \n: > on L oler i: r o te s te i : ¡? c 11 cT.: o an .1 allowed
to c- c: 1 ir tho o vc :
1 r> j :pl e of e .r, h o o, J. a:: - o o. b v o j s
1 sr XIc.1 o of e;.ci 1.. .v. 1 to 1OC: 1 j ibr 2houus
1 r-o.i;.-lo o.f each he atol te ppOi; :J fee hours
1 :. aia_ i c o i' caen n o a t e to l 000 f o r 2-'! no u i' s
2. xv/o ssui; l'-s 01 oh o id i en and o i do hr; ex- lato
Ohu.r. t ( f l y:,¡ ;: .0 c or0 Jo; s on L: .h ch -r t uf d ub ov o )


71
strength which occurs when specimens are removed immediately
from the hot oven is due to stresses resulting when the mate
rial is exposed too rapidly to a cool environment.
X-Ray Diffraction Pattern
Twenty-six x-ray diffraction patterns were run on
13 different samples of heated and unheated cherts. No con
sistent differences could be detected indicating that no
change in the crystal lattice occurs (see Figure 14). The
slight difference shown is well within the range of experi
mental error. If the crystals were coarser, the peak would
be higher; if the crystals were finer, the peak would be
lower.
Differential Thermal Analysis (DTA)
The method of studying materials by differential
thermal analysis consists of heating a small, finely ground
sample at a constant and rapid rate, and recording by suit
able means the endothermic and exothermic effects. A dif
ferential thermocouple is used to detect these effects.
One of the thermocouple junctions is placed in the sample
being studied and the other is set in a thermally inert
substance that is undergoing the same heat treatment as
the sample (Berkelhamer 1944). The electric current gener
ated by the differential thermocouple is amplified and
recorded. Endothermic peaks result if the sample is taking
on energy.
Samples were prepared of pure quartz, pure opal,
heated and unheated Johnson Lake chert, High Springs chert,


80
heated
Figure 1?.Surface Topo raphy of Unheated
and Heated Johnson Lake Chert Samples as Viewed
by the Scanning Electron Kicroscope (Scale: 1 inch =
254,000 A),
unheated


66
both of these s; 3G1. ens as obsidian based on certain arbi
trary attributes shared by Doth; the use of other attribute
may have resulted in a diflorent catogcry for eacb, Of sxg-
nifinance here is the reversal of the arcant of pressure needed
f05* fracturing the material depending on \;bether the rod v;as
removed from a hat oven or \;&s first allov/ed to gradually
cool in the oven,
Point Tensile Tests
A vas machined to apply stress to the ceres as
described by Ssichuuth (1 >bj;)< This jig vas used in connec
tion with the .diehig Universal testing machine described
previously. The jig v:as constructed to apply point tensile
load to the curved surface of the cylindrically cored sped-
men with the long axis of the specimen placed horizontally
and at right angles to the loading jig. The jig u-=s con
structed so that the point comprensivo loads were applied
through small diameter steel hardened cov.el pins vito rollers
menu fro tu-vod by Hole-Crome of West Hartford, Connecticut
(sue biguvc J h;, The cones of percussion induced, at the
points of r.v; pi: lent ion of compression produce internal tensile
stresses perse'vgiculer to the load axis.
C o m d s anni e o, one in c h i n <1 j. a? ,e ter of v ary in g
lorr;111v:o:ve repa^ad as described ear-1 ier, In the first
e xpe rime n t, t, o c ore d spe c inen s o x Oc v 1 a c ie :c l v/ere he at ed
to OO'-C for fb hoars and re nove d immediately from the hot
oven at the- end of the heating period; tv/o samples wore
retained a: un c.atc cc.. tro 1 r T\i re0..Itj o f thi r


43
is not tas.-d entil'd;- or intuition (av sea si-, on
Tests}- It regains te be ceoloined, b/rv.sc, vix; it is Vi: it
it fch- ae.-'ipi.ratiao is j.'isod too rapidly, explosion oc--
The criminal isight lose at lOC'd is du< to the resit v of
afhor-bod water held or. th. --us :t oes of the inlivtai: x -ic'-o-
c.oystals. After tils initial 1 sr,c '.face:, loss, tv-o
rereinG quite stable until J3DVC .¡'"ice t.e this, the to: -
or-aturo ;-rebat; has not tn on hi. h eheuph to i'OJto"o th-.;
ehe.Licaliy lumnd v/r.t.-r held in fee in isor.-.r-ystall j.-, ret: -
1 suspect that the folio-.'in; hap ei's: J5C0 is ; : : -.
ouifi t-ioutlj M;,-h l..- fox- altam-tbon he i.e plo.c.
if this 'toi:ijtor--:.tui'0 is si.u;f .-ir efor u Ion; peri."' f tino
{sac Tallo -C-). If the te:-poraturo is raised to 3 piier
to the radii.1 retoval of the ci.e*.icell; hours eater,
j>i03ir.ii results becc-iss t'no -.Iteration preseeds tc.) rapidly.
Vitrification is always cviic-at, at least to ser..o extent, oi-
tae fr-aoturee. surfaces which result eren those exp'1 osion:..
Therci oe-e, seno charra, -.ust occur alr.ost iu.o iiato-j; v:i.o;i a
critic'1 tc-:".oeratu..-e is rc-.-che i even thou: ii i no i..r.tc-risl
Tiloi.-a Us at the sore tino. There doce rot seen to bo :iy
y rcr'ic.-as study srlh:; v.-i th thin /.roblen a'-.equato!;;,
Trosbc:: in his article an bv- r:.r its .- of pifies is-
cu-ine; the :-.iCt that class; will :".v:-c n.r: i.-hc-i; nlt'-mate-iy
.ubjeotaS 1 o hour, r.d col-.'. a..- -J... re-:-'.: e-ati; df. bribe;;
the lvpe o; fracture i.-hicf .-i 11 sec it d.:*.c-:.dinp; o: the stmt
to uhtoo re. tor-ini in eubj osr.-l. ih.-r-ha; 3 the answer lies
iu t.ho full of up r, tats-, eht;


51
needed to transform microcrystalline structures to a non
crystalline form, the vitrification which occurs when flint
materials are heated to only 350C must be accounted for in
another way.
The impurities in flints generally act as fluxes,
due to eutectic developments. . .
. . Fe20^ was found in all flints varying from
O.OJ to 0.12per cent. While iron is objectionable
as an impurity because of its discoloring effects,
the small percentage present in the flints would
probably be of no significance in a body composition.
Some of the American flints are free from CaO, and
others contain generally less than the French flints.
The loss on ignition varies from 0.13 to 0.85 per cent
and represents C02 dissociated from CaCO*, and ad
sorbed or chemically combined water (Pressler and
Shearer 1926: 292-3).
If the impurities (or combinations of impurities) contained
in Florida cherts are serving as fluxes (substances pro
moting fusion) to fuse a thin surface film of the crypto-
crystals, then change will occur when the melting point
temperatures for these impurities are reached (eutectic
development). If this is the case, answers are found for
two puzzling problems: (1) why vitrification occurs at
such a low temperature (350C), and (2) why some materials
do not respond at the same temperaturesthe melting points
of the fluxes are probably different. If the percentage
of calcium is quite high, this also explains why certain
materials do not make a desirable change despite the
temperature or length of the heating period. Calcium will
serve as a flux if present in small quantities, but pre
vents the desired reaction from occurring if present in
large quantities. Three Florida cherts which responded


2-1


'I
1 £ o <11 ve:: v r :> e ¡ t i i; j ;~I: i 1: -i -1L- r-.t t o r- x, o
t: : 1 a i n v;::ja a s .c? n ; ;a r a v i a el r :l n. r, o £ £ i hr ov c: h h:ut iu g:
the opal when drieC -Gold crac..t aru adhere ir.c..-e i\vn:J.;y to
ti: o :r.lc voerystels e.xac.tj y as .1 ello revi Id te vid to stick bo
tie side of a glass. This n.:-nht resal n ir a Mao. i fig of the
i*i i.c r o e ry B t a 1 '. T h a p re s c Ac o o f c pal a e in t a re t i i: 1 .-. ]. r. ; f o -
i*iol in cho.Vi liowovu has been cuite v.orou^M- hiss issn.*:
(ovlh and V&cvc: 1932; Schrulw IpGO":. Acte ,pto to detect
the presence of opal in this study produced on;;, relative
vos a?, ts,
lie s; j it c ; h e disc our o g lug c o:.ugc n t s f 11 us far .. i a c loss
of ' :itei* v.'liich occurs uhen che-rts arho at,i i.- a ve c y
si:?v!.ficant factor in the alteration of the rock Vitb the
re pc val of the intercrystalline water, the jta.c. roc rgs tais be
Cere flrM y cemented Tims when a fracture occuie it paste.;
through i-atlier than around the individual crystales In
otMx ronde, the stone breaks noro like glass than a rock
apf-tepate even though the sat.e niorocrystalline g truc ture
an 0 t e M. u re are still p re c e r> t Tb. i a in t urn e na j n 3
th... :ir*. y :i;¡ vi121 -. ous,.eas of tTie frcf -.ired surf ae: .
C x'. c t i *?. c ^ f r:;i c r r. cy r ; o 'J o ,: a i c h c o;. c t i i v v v. i he
t;.i c re 1 ,h :ie; e :.n ov:n :s c h a 1 e od ony, 1 iin ;:: 1 of i c a 13 j, c he 1 -
c e d on j s ! cvy r gr c asp i n 1 us t e c h v i, in. d i. i ", ;L f a c c j o f
11i j iii j o.-. > r.O t Lv- no r... ; 11 / n o f s e -: r\ b e c .s; o the c. p t -: a r*c?
anh i; i; ( v. o d o f i n 5 t a chape o r o v i en t. t- .1 on ) u s *. *: \ 12 y a ub
o cj u i i i. i c; -:..: a j i . 1, a n 0 i j c. rosco; ic vli . r e f o ' c . o n f j'a c t v< re
occurs, especially if the ro< A i ccara? grair^d, t i; ?


; i. f j i .i en at I; c ir; p re dio t Ara.; ture. x¡ ie re f or o ,
t h ~ " y 1 u libo . ir.e! .* \ i r> 1 j ; h e ro fc- j> r o l i o t ub 1 o t he
fracturo. He ate d cherts a .ve ir: _ re y 2 a s s ~ 1 i Jce an d Ir a o ti lv o s
are not only more predictable but easier to execute
1 ron Content- of PI oridn Cher t
The ?ncorpore. I3 on into cr.ort f c .moo ion.? o V oor.ee.:- -
t r ato on 3 ol i ron v/h i c h i md art a p i n a t; c r e d co3 or up on
heating is usually becan.ee of secondary enrichment resuitir
from the nobility of iron in iron-rich, pule os oils or bey
deposits. In some of the Lover Miocene deposits, hove vox*,
another situation exists in which iron seems to have been
in cc upu ir ate 3. at the ti^e of .-ilicifi cation vhich re suited
in the chert formation. In addition, although they are
r a re br i v; at pinh colors ( c a 5 11 7/^ ) ( Mun s a 11 194- b ) p j e
sometimes found in cherts imbedded in terra roes:; residual
so:* 1 a or. Ocala Limestone. The?e cherts o*<%?: dul 1 or earthy
in eonversnee and do not resemble cherts which have been
t h e AA'A-ly cite r e <3 ( H. K. 3r o c v s, pars c n al c orinar. i c a t i on J .
Color change tabes ol ce between fuOC ar-d 2C-C,&C
in } or:* d a c hevb3. F? pure 2.1 i ] I\\ t re i e a ahs v ari ai j or.
oh" r : su t r. ;] e ^ c ¡ic* in uon tr o ?:aou n *: f r or A ro 3cr t
in ti1 o r.ava lc Urfori m._ t ,ly true col or re;u;*- -ven t:auicn
not atocinad at on ore: ,-j 3 ol th- i 'ou centeno (sec
;v: pl-.s e i n i 3 ; u re 1C >} r *. vea j. o u t n s< up 3 o c V. v i 1. n a, fro.:
10 Y i G. t /I ('--or a- e a v. / j r.;11 n o r r. e and -. ui o o1 I o wi r h
bro- n but l-juAT the- ' v .. to 10 u h/4 (betv/c-jv p.-Le
r :K. V -o.I dvr. r i:;:: ; r-r : ) c crin ir1 ? ' t '.u n-a:


o Cl
TABLE 10
RESULTS OF POINT TENSILE STRENGTH TESTS0
,-la
¡
Obsidian
j o-.'" 3 or. Lrlrr
cr.ert
3072
1 300:;
350 c
400'"0
Total bCnen^th
Lose
Aliov.e
cl to Cool in Cven
1 2640
1536
2262
j
1116
1368
-
2*48
2136
1630
1584
! 2^72
1680
1392
i 1512
2016
1392
55
Senoved.
from Hot C\
'on
1125
1104
267Cc
1544
1
r"iEsto of load was app r c :* i r i ;¡. o I;/ 2000 lb/irj.
The results err. not consistent.
It is difficult to explain tills anomaly Kith v;hat otherwise appears to
significant difference.
-3
Q


1
17
. Europeans who first encountered the American
aborigines were concerned with, matters other
than stone technology, e.g., survival in a new
ecological situation
2. It was more fashionable to record esoteric cere
monial performances than the practical aspects
of native life.
3. Iron was almost immediately substituted for stone
in making implements; in fact even prehistorically
in the Southeastern United States, arrows and
spears were often headed by materials other than
stone: bird bones, bird bills, fish scales, fish
teeth, fish fins, animal bones, animal teeth,
horseshoe crab tails, and oyster shells. Some had
no separate headthe wood or cane of the arrow
shaft was merely sharpened and served as the point.
4. Since chipping stone tools (except for gun flints)
was not part of European technological knowledge
at the time of contact, not enough was known to
observe or describe the procedure accurately, much
less interpret such an alien process.
5. Most explorers, adventurers, etc.,were not among
the Indians for extended periods. It is possible
that this procedure occurred only at special times
or in specific locations and was considered too
mundane to mention.
To establish that desirable changes do occur when
siliceous materials are subjected to critical temperatures,
it was necessary, therefore, to turn to nonanthropological
literature. These publications will be cited in appropriate
places in the section on Methodology.


23
Heating Experiments
All of the experiments involved the use of heated
and unheated specimens but it was necessary to create a
special category describing the many and varied conditions
under which the rock materials were thermally treated.
These tests followed what might be considered an evolution
ary sequence since the results of one experiment often
dictated the need for another which in turn suggested still
others. As pointed out in the Literature Review, only
Crabtree and Butler's (1964) article discusses heating of
siliceous materials from an archaeologically significant
point of view; therefore, these experiments are of a pioneer
ing nature.
Weight Loss
Twelve 1-inch cubes, each weighing approximately
42 grams, were laboriously prepared to be used for com
pressive strength tests. (See heading entitled Strength
Tests for the description and results of this experiment.)
Six of these samples were treated as follows. Two 1-inch
cubes each of obsidian, silicified coral, and Ocala chert
were weighed prior to subjecting them to heat. They were
placed in a Blue M Lab-Heat Muffle Furnace, heated to 100C
for 48 hours, removed, placed in a desiccator, and weighed
after they were thoroughly cooled. They were then reheated
to 100C and left an additional 48 hours to determine if
all the moisture that would be driven off at 100C had been
removed during the original 48-hour period. It had been
removed, as was indicated by no change in weight. This same


10
Thu- j oh ..-re appears t ... 1: : -m. j on
.from .fouryoean sources than f vcn tin .;?o-y hov.. vo,
t he fo 11 cw in & ac c oun t o or:c o r n ir_g t he r. d . o an 3 s i and a r s
deiiic-ns traces that the mienriccoa 1 ha aiincr a.7 a 1.cre to c: r.v-:jo
alterar ion nos nob in'.\uo;ai to ^vrtola r.-roups in the Old
World,, This is even the acre intox'-'stino, since the .Andarn
Is :i c ne ri; ver e ropor t e 1 t o n ve rJoi a v' e 1 ,e o.7 bcm to
iv.ir.lle fire*
Chaps a.nci *i ricos arc. never used no re thrui once;
in fact,, several ere -geno.!'. ,11 y employed in each
operation .'si-.kinf; is rorandod as one of the
ciu t i f: s o f V; o:1 jj : n'J is uf o .a 11 y ps rforned by then;,
h'or K5: r in.; cl: due t v; o p , o e r: c- f v hit y qu ar t a a re
ne-edvd; the stones are- no z pressed syainnt the vbiyh,
n or a re t he y bound r o s:. d tL j h ti y s o a s to in c re a s o'
the lino of least resist--see t o the blow of the flrdce.v:
rrj t ciie of the pieces j >.. : ivs t he atc d rr-.rl a f ;ygrvav-ds
allowed, to cool- it is then life firruv and struck sc
right aGgibs; with the other stone: by this eear.s is
obtained in fe,-; rerents a r. arbor of f'.'a;:vents sui!;-
ab 1 o 1 o i* t h e p uro o s c a o'*ov & nonti on 560).
A paraphrasing; of tins q act at .ten is to bo found in
Jas on (1 Sy ;*: 135 7 ) *
bao of kire in Onv vi yjf \ .. C:p.-i -
T j 3.0- i; >. f o ri:> a t. ion con t a*j ne d i o thi j c a 1 ec > v y c csi e s
fro a a.r;. . i ia j ol c j i c o 1 o ;. :-v a t i on ? ns c e a t
quur -M! *i tc; v ao 3 or in opsr-ati.or. a
The nost vj?.i.;ly qr.O'Vd nta of fire in aberipiaa?
quori s* o j s that of r'ovic^ ir- hIn uesc?; ntoc IP int
Hidye. Crio'
. # 'Lh- -3.c.;- s o f C i rv v;o) e pj. a in ] y v i a 5' >'! ; J a l h o
v' v.3, fro! v/hicb the h- f "'o'.: is a -.. ;;uv-,. that firos
wi.iv ei.ii t up.-p. ire rohq vr:! ch-r -j. v*;hi3e her. Led,
v li *. v r -. .. 3o :/j; ; a 11. r.:.: c i: or;o c ou 1u bo
orole. iii to p.i.c.a: (Wilson 1897: 870),


63
TABLE 8
RESULTS OF COMPRESSIVE STRENGTH TESTS WHEN
HEATED SPECIMENS ARE SUBJECTED TO A COOL
ENVIRONMENT WHILE STILL HOT
Sample
Unheated
Control
(psi)
Heated
(psi)
Strength
Loss
(%)
Obsidian X
50,100
30,000
40
Silicified
coral
43,900
25,000
43
Ocala chert
52,994
31,720
40
TABLE 9
RESULTS OF COMPRESSIVE STRENGTH TESTS WHEN HEATED
SPECIMENS ARE ALLOWED TO COOL IN THE OVEN
Sample
Unheated
Control
(psi)
Heated
(psi)
Increase in
Strength
(%)
Obsidian T
31,100
39,600
25
High Springs
chert
25,100
42,200
40


Decrease in Compressive
Strength
Increase in Compressive
Strength
Ocala Chert
Silicified Coral
Obsidian X
High Springs Chert
Obsidian Y
50 1 Jo 1 J
I t I
10 0 TO
(%)
Jo 1 5 40~L"5I0
Figure 12.Decrease or Increase in Compressive Strength over Unheated
Controls of Heated Specimens; Samples Showing a Decrease Had Been Removed
Immediately from a Hot Oven while Samples Showing an Increase Had Been Cooled
before Removal.


78
from Ocala whose grain size is intermediate of the three
samples* Most significantly, the Eocene chert from Ocala
that had been heated showed a marked reduction in the
granular surface area: 1.90 M /g compared to 4.86 M /g
for its unheated counterpart. This represents approximately
a 60% reduction in the granular surface area of the heated
chert. There is no question hut that the microcrystal
line surface area has been reduced in the heated specimen.
This was due to the reduction of the intergranular pore
radii. In other words, porosity had been decreased due to
a fusion or intergrowth of the grains.
A computer printout showed the size of the pore
space distribution and surface area distribution relative
to percentage of occurrence. The plot for Ocala unheated
chert showed the minute size of the original pores: 27.81%
of the pores were 23p. or smaller in size whereas about .14%
were 370.8vi.
Scanning Electron Microscope
The scanning electron microscope (SEM) is used to
study surface morphology (Krinsley and Margolis 1968).
Small flakes not exceeding 1/8 x 1/2 inch were pressed
from unheated and heated cherts. The samples were cleaned
with acetone and mounted with Scotch tape on an SEM speci
men plug. Three or four specimens were mounted on each
plug. The freshly fractured surfaces were exposed for
scanning. The specimens were then coated with gold "in
order to make the surfaces a better conductor for the


TABLE 3
RESULTS OF EXPERIMENT CONDUCTED TO DETERMINE ABILITY OF HEATED ROCK
SAMPLES TO TAKE ON MOISTURE
Samplea
Weight Gain after One Month
in Moist Sand Bath
Sample3
Weight Loss of Control after
One Month at Room Temperature
. (%> .
24 hr after 4 Days after
Removal Removal
(%) (%)
Ah
57 .53
Ah
.01
Ah
.45 h .42
A
.06
As
.27(lost) .39(lost)
Eh
.00
Eh
.95 .2?
E
.05
Eh
1.13 .35
Fh
.00
Es
.55 .09
F
.08
Fh
.18 .15
Hh
.08
Fh
.09 .03
H
.08
Fa
.04 .00
Nh
.01
Hh
.56 .44
N
.06
Hh
.72 .30
Th
.00
Hs
.42 .21
T
.00
Nh
.2? .21
Nh
.26 .18
Ns
.12 .01
Th
.44 .36
Th
.44 .40
Ts
.28 .18
following the sample letter indicates that it has been heated; s fol
lowing the sample indicates that it was soaked but not heated; a letter with no
h or s following it is an unheated and unsoaked control. The tremendous difference
in weight after four days in the E series may be because it is more calcareous.
DIt is difficult to account for this anomaly unless an error was made in
the original weight.


au*j¡s-3 r u: >: 3a?;q ¡;nc¡* r> T 2q
O Til \ r' > y*<-. i- t r\.-
v;j ; f
o ; , ?-:) " o
O .: ;D :> J ¡ u W 4- OVJN5 OVM Y) ¡JvD i\> H* ?- (\J-0-vJ (.C
M
. I ' ;V :
v r* ; }
Sample
! > ov;
cs o w :v ;v, o o o o o o o O O O O , o O :; O O O ; 5 J j o :
> \/¡ ?- V 'Ov.1 vVKvOC'i eu PON? -* Pi'-S l~M.>: ' D C- '' f:
<> c- ;-.i i O
> *: ;; o o o o o o o c o no on no o o o o o o o ¡-' o
-O';'j'1 -.;iw i'J'v.x V/i(Vt )-'o P 4 -1\> i\> h- \? <\> f o \v.
!1- -J :.* r,
o N ." o
; v
;-! i
- o H-
.5 O O O O O O O O O O O O O O O O O c O O ".5 o c? *:*
j\*i .-.iv-j .o ¡ovji (- *-j vTi o i\?vx o rov4 ^ o o i\:w rovr* :
!
:-0 '> :
v V; ,
-y b ; o
_fJl4 3
!^gaS8¡3S8S2kJ88.5ISP38SS^?,SJ?1|i,.'i; 3 lj
; 1 o :
. s 3 .i,'(? O ?J >- O O O O r. o oi-o w >- O O C O O O !- O 1 '-J \ -O O ' I, o ¡S
r- : Ovo o-'-'ivOO'i O-O. f.u > i.i pivavu-o o~> mj 0->; ---'j i ¡ ! I:
;; >\>
I.
_ 3 ¡_.. y-1 ji <../ j... ! ¡../ j -j > > i- r o 1- .
v.T-.n OVi -_} O ;;* J :\J O vtj <7\ r\;\ -r- \ V V 4-/ :
: -- j
. V'H
I
v ro
, V'J -i
. r a ,.
J;
! - o !-* on o fJ ^ *- ; m c- ¡-* o <: > c- v-< ^ ? t-j:
: C' ov.-! OV'y < '-o ; -.v -.ovr-vO vv r ou> c C' i 1 Of o' ^
i ; i;
!:
f *
e ;> ; } /:
r*! . - *- !* r. - - o 1 ; ; o
n ¡\j f-: .-y > :*ov.n f\> v rv 0\^ n (.- o o r : m vr* j -
b C:
n--~ i.' ^ j. j u >. < c | j


12
charcoal About 20 per cent of the chips and 10 per
cent of the large blocks were reddened as if by fire,
while reddened fragments were abundant in all the
fire-places. Nothing was surer than that fire had
played a great part in the quarrying process; but while
four fire-places examined showed no trace of cooking,
they also gave no sure clue to their purpose, and there
would have remained a doubt whether the fires had not
been built for warmth had not a fifth hearth dis
covered in shaft 2, at a depth of 15 feet, seemed to
settle the question. It was an oven regularly built
of blocks of jasper and contained a mass of charcoal
and ashes. The fact that the sides of the blocks were
reddened, and several had already split through the
middle, while the interstices were filled with fine
splinters, offered conclusive evidence that the quarry-
men had built the fire to fracture the blocks, which
measured 2 feet, 1-1/2 feet, 6 and 7 inches respec
tively in diameter.
My experiments proved (a) that if a large block
of two feet in diameter is thoroughly heated on a
wood fire it breaks into numerous pieces at a moderate
blow; (b) that only the fragments near the fire are
reddened; (c) that the fragments lose their original
gloss by the process. The luster, however, seemed to
be regained by long burial in damp clay, as was indicated
by the high-polished fracture of some of the reddened
chips found on the fire-places. Moreover, many of the
worked forms gathered on the surface had been probably
fire-reddened, and it is not unlikely that the Indian
could have so heated the blocks as to reach their purer
parts without spoiling the whole, while many of the
large and coarse blocks might have been fire-fractured
to get them out of the way (Mercer 1894: 84-6).
Oakley (1969 personal communication) says "I have
come across evidence at several localities suggesting that
stone age craftsmen sometimes obtained flakes of intractable
stone by using the method of 'fire setting,' ..." Also
At Hangklip on the coast east of the Cape Peninsula,
South Africa, erosion of peat has revealed a Late
Acheulian factory site. At the base of large blocks
of Table Mountain Sandstone protruding through the
peat there are quantities of large thermal flakes,
and on the surrounding ancient ground surface there
are many broken or incomplete hand-axes and cleavers
made from such flakes. Professor A. J. H. Goodwin has
suggested that Acheulian man obtained the flakes by
the method of 'fire-setting,' that is to say burning
fires around the blocks of sandstone and then dashing


is
Chert. bcir'V; ='oo'., v'ries .r y it:, jhy 1
charac terirt i;;r even iho^hr.:'.;, i;: ts tbo :r , ato
crystals of quartz are un?. .Co?;in charec cor. The fao tors
that determine the physioat proper-tiss of cherts aro;
(1) the £. i r. e of t he qu .) r t v, o r y : t e 1 s, ( 2; h c/w t >* ;? ache hr o 1
cry w tais i:L t t oge t her a fa s o v ini.; p or e s i ty and .far a c tr.ro ;
( 5 ) t he am o un t of f o re i gn me t a riel p re s c n t, iooc.il replr c. e -
merit s and o the r he ter 0£n cities in o ru f 1 nr e o:; c our c c;
(h) void spaces; and (S) crystalline faerie (tro crystal9
are not c quid :i mens ional or always randomly or-iejded } s T-r\ ?
in the FI or id a c he rts > there are d i t f or ant t \ pc s an 1 ev ; v\ '
sin pie nodule is not necessarily korne^ aeons throughout a .-
mass.
The lithic rav nato rials v.cod almost oacluci vc."f in
t hi s s t ud y were Florida cherts. Jus t f ic at i ons for as i ; c
giro ral torn such as client aro as fcl3ows To this author,
o. t T: o a a t t ho t c itj f 1:1 n t indicates an e rxt r em o .1 y f ? j materiel found in the chalks of knrl ar.d. Also, as stated
V-bovg f 11 rft is usccl as a comr.on doci;; o a tev for- e rtifee ..:
with nc specific material intended. Usin' iV> modifier
hi oyydr. prre :ir.y lh>? uord chert calle to rind a pnrliev lor
typo o f me t c iw :> I :nuc r a 1 rkan ss n over. ill it e Penn sylv en i a
jc;.?:rei-, or Euylish flint does* Thc-uyh there is a ran ¡ye of
differ Jr,; to:., tres and homo or, cilios > 5 lurid a che its v/.:r_- al
formed uude:- siiailar conditions and share common character
ise ic :- ;.ti ic h di s t in:y; i oh tliex: f r oo t>c r s i 1 ic o uu ' r oc< .
j:- c ;*o -.uM o :) u;.'h c r o .i coi. d i i i : i ^ d o r v: * ah c h r: t
v.Ti 31 for:' ; > J. c r i.dc :v. r t r c c c '< *; '
as a ru rid- iv for ; ci->du


55
Figure 8.Examples of a "Crenated"
Fracture which Often Occurred when Specimens
Were Removed Directly from a Hot Oven to a
Cool Environment.


65
siliceous ¡.¡aterials are heated to tejera tures of 400 C
5G00 for sustained periods and removed while hot, certain
stresses occur which c-eusc a reduction of strength when
compared to the unheated controls. The three unhooted
varieties vri that cod forces ranging from 000 to 53 -Oi'O psi
( t o u a d e d. f i ; uro s ) v;hi } e t he he a t e d s amp.! e s c :r' he s a' e :::i a to
rris ivvp-jcd from 25*000 to 5?COO psi. This rorree-:rite
v .'proximate ly a 40Vj reduction of strengbb in th- roamed
samples. On the other hand, when the heated campjos /ore
?11 ov/od to cool in the oven, as shown in Table 9, there
wbb an increase in strength amounting to cipproxjmatc/iy
25/* for obsidian and '!Op for the 1:5 g;h Springe chert.
Cohering the material without the introduction of strcasas
allowed the heated samples to resist failure fox' a 1 on per
time t o a n un he a ted counts rp art s ox- he a t s d eu e c 5 r,i-? u s t hr t
.-..d been stressed by sudden subjection to a cool onviron-
mo nt ,
Ko coreorison should be made between the pounds of
provoca>; per square inch recorded in Tables 8 ar.d 9- The
cape ri"¡~ ate wore conducted se-vcrol month;.' apart, the equip-
ment ; o:>raud by d*j fforent in<5 ividuo 1 s, and the roto cf
1 o:.-.d i.r s n c t eb c c i'/ of i c_ th e s; .ip 1 o a re rove fro to the ho l
o\ on an d u ¡ i o :i. v con t i-o 1 v. The .* i L; y o f 1 o a d f o r t h e Tab 1 e 9
seo-p 1 c'* ipjroni:1 ab' Xj 20,CCO ou:dc pc:* u: i vte In
r vice., .*> d r o ,* \ imp o r t a. 11 j. y, bh e s a 1 o r> r ; r e different.
The c 'sid5 en ?;; up les werc f ron dif feren ] ocati yna ano
t here f c re pi- o b < *.b 1 ,/ c* 5: d 5. f c re n t a - o: n > T ti e p o s 51 i o o 1
a i:i . V -]jc rea.c-i 3 re ': d; 1 i h t ' on har; c3 n r: 5 f icd


85
been flaked subsequent to heating whereas the vitreous
area has been (see Figure 19) Soil conditions would not
produce this type of differential preservation.
Color change which occurs at a lower temperature
than the significant change resulting in a greater ease
in flaking, may be considered a reliable indication if
accompanied by vitreousness.
One other suggestion is appropriate. If local
outcrop materials differ in texture from site specimens,
it is a simple task to heat the local materials, fracture
them, and determine if the resulting surface resembles
site materials. This is how Kr. Crabtree first suspected
the thermal method had been employed (see Literature
Review).


BIBLIOGRAPHY
ASCHER, ROBERT
1961 Analogy in Archaeological Interpretation.
Southwestern Journal of Anthropology. Yol. 17,
pp. 317-25. AlbqerqueT-
BERKELHAMER, LOUIS H.
1944 Differential Thermal Analysis of Quartz. United
States Department of the Interior, Bureau of
Mines, Rjport of Investigations, No. 3755^
Washington.
BORDES, FRANCOIS
1968 Th Old Stone Age. McGraw-Hill Book Co., New
York.
BRANNON,
1909
COOKE, C.
1945
CRABTREE,
1964
DEERE, D.
1966
ELLIS 9 H.
1940a
1940b
P. A.
Aboriginal Remains in the Middle Chattahoochee
Valley of Alabama and Georgia. American
Anthropologist, Vol. 11, No. 2, pp. 186-98.
Lancaster, Pennsylvania.
WYTHE
Geology of Florida. Florida Geological Survey,
Geological Bulletin, No. 29. Tallahassee.
DON E. AND B. ROBERT BUTLER
Notes on Experiments in Flint Knapping: I. Heat
Treatments of Silica Minerals. Tebiwa, Vol. 7,
No. 1, pp. 1-6. Pocatello, Idaho.
U. AND R. P. MILLER
Engineering Classification and Index Properties for
Intact Rock. Technical Report, No. AFWL-TR-65-116.
University of Illinois, Urbina.
HOLMES
Flint-Working Techniques of the American Indians 1
An Experimental Study. The Ohio Historical Society
Publication, No. 72. Columbus
The Possible Cultural Affiliation of Flint Disk
Caches. Ohio Archaeological and Historical
QuarterlyTTol. 49, pp. lll^ETT Columba!"
92


1
L bur p-'. .ns uo first .co. .v bh,. re.- m
al: c ri: ir o ?. vo ro C or o c rr1I vi : 11 o i i o v
than a ton j iec 3' ncleyy* c £ i surv 5. ar a new
eco! o y I coa si t ut i or? *
2, It vas nore fashionable to record cooteric cero-
ii-or.iia.l pi ;>"orut^ices thin to prec-t:lca.l cspects
of nativo life.
3. It o: i v;h e al u.o:rt in ..if d J. -j. i 1 y .rab o t 1t j. t ? in ii.cki'ivy 1c ten Is : nn facf .c:r. /rollis borient3 y
in the Sou t}*eos cr; i V- ,.i te I a t e o r.rro1. o end
s pe r r s V? ero o ft ; n h e',-l ' b y ?. fc e r i a I s c t::: r- 131
s S c-.n e : b.1 r c. b o*' e ;>, b i re o ills, if s h ol ^ r ; fi.h
t er/dij fis b f i r. o, air iv al be n c s s ar. i rea. 3 c e e t h *
h o i* a e oh'^o c r ab .. _ 1 o an a oys t e r- e La 31s, ; Jorro h a J
no separate hoad-the wood or care of tbr. arrov
shaft was r. truly oh arpan oci nnci served as the point,
n. S:i.no e ehip > iny s on e tools e:*:ocp t for r-rn f 1 i.nts )
;;as not- p;.rt of iurep;?on tochnc 1 e; ica 1 ¡t?tj cdyo
o. c t he t i.: o o f o or-, t ac t; r.t o l on o \ yh vas I*.j o vr, t o
obco r vg or docrib e t. : / \..:-oc of ure ac ciir^t o 1 , :;:v.b
less in t e rp re t :. v.c h an a I i en p r o cose
3 . Mos t exp3 o ver'3 } advent are r s} e t c *} v;ere n na n or y
the Indians for extruded periods* It is possible
that this procedure occurred only ct special ti.vcc
or :lr. seecif ic 3 oo>..ticns arid .as considere.d voo
i:undone to xen l;J on *
To estbil oh that desirable chan poo do occur wlien
e i 1 i c u o y s u c. t c ra.l .e a re s ub ye c tod to cr i t i. c & 1 t err e r a t u rv. 3 }
j.t vas n: c!.*c r ary} therfcr3, to tu.cn to n onc.ntir;:po3 ori o al
1 it era t: _ The s publ i cat ion r *:i 13 be o i to b. approp ri.? t u
pi aecs i n t'v.. nection < :i Hetbodo 1 cs


13
water on to the heated rock to cause exfoliation.
However, as far as I am aware, no ashes have been
found around the blocks (Oakley 1955: 45).
This report is particularly interesting since it
suggests that at a very early time man had a sophisticated
knowledge not only of stone fracturing processes but also
of the use of fire.
Caches
For many years stone caches consisting of arrowheads,
spearheads, grooved axes, polished stone hatchets, large
chipped flints, spades, etc., have been reported in the
literature and there has been much speculation concerning
why these were deposited. It seems perfectly reasonable
to suggest that a flint cache as described recently by
Hammatt (1970: 141) was used as a p&leo-Indian butchering
kit. Other suggestions that have been encountered in the
Literature are that the stones were (1) buried to keep them
moist; (2) buried to hide them from enemies; (3) used as
grave goods; (4) unfinished preforms to be completed later.
It therefore is fair to add yet another suggestion: some
"caches" existed because the buried flints were being therm
ally altered in order to make final chipping easier. While
only a small number of descriptions mention the presence of
charcoal, it seems plausible to assume that a farmer plow
ing a field who uncovers as many as several hundred flint
implements at one fell swoop is not going to stop to notice
that the pit also contains evidence of fire. Therefore, the
number of references might be multiplied many times if the
excavations had been conducted in the mid-twentieth century.


SUMMARY AND INTERPRETATION
Despite derogatory comments by experimenters who
have "proved" that subjecting flint to fire has only destruc
tive effects (e.g., Pond 1930; Ellis 1940), enough firsthand
accounts exist (e.g.s Schumacher 1877; Powers 1877; Man
1883) to warrant investigation of the technique.
Extensive experiments conducted throughout a two-
year period, in which flint materials were exposed to heat
under numerous diverse conditions, have demonstrated that
the alteration of siliceous rocks, when critical tempera
tures are reached slowly and maintained for a sustained
period, probably conferred an advantage to prehistoric man
in manufacturing his chipped stone implements.
The oft-quoted method of dripping cold water on hot
rocks has been largely responsible for discrediting fire
as a contributing factor in flintworking technology.
Attempts by this investigator to "chip" with cold water
produced no flakes at all and resulted in a crazing of the
rock thus confirming the findings of Pond (1930) and Ellis
(19^0). However, if one returns to the reports of Schumacher
(1877) Powers (1877) and Man (1883), they report removal
of rocks from a hot fire after which they are shaped into
implements. The only objection to these accounts is their
brevity. A more detailed description or closer observation
87


97
of Xlorida durii; the fall quart-. , 19/ and the ./into
quartor, 1971.
Barbara .inn Purdy is married te Laurence henry rur-d
ano ir the nether of four children, re is n number of the
hmc i: i c r a An l h r o j; ol or 5 c al A s b oc i at i on an d 11 os a oc Ae 15 for
Ann2ican Archae o 1 cay,


56
Figure 9.Specimen Depicting Intentional
Fracture with Bulb of Percussion and Typical
Fractured Surface Emphasizing that Impact Has
Occurred.


TABLE 5
EEOOsTS OF SXFSFTFCOKDUSTED TO DETERMIliJS ABILXT 0? HEATED HOCIC
SAMPLES TO TAKE OS H0IST23
Sony le a
Vo i I,fit Craitw'* One Mod-1/*
in I-eifft oir.nO
t .... '
Sample a
" .
Weight .Loss of Control -After
Ons ;loath at Jtoon Ten-sraoiu'c
J/=)
?ft hr afeen ft Days after
Henoval ic.ioval
(;} 0-0
7? 53
Ah
.01
.1; ,f
A
# WO
J.C-
.27Qost> O(loot)
Sb
,00
y.'a
tqr- 2'V
S
.05
.Z-i\
Fh
,00
Ls
..53
-
c.
? h
.18 ,13
Hh
Or
*h
.09 .03
K
.08
j;\n
, C: .. CC
Oh
.. 0/
T-1
. VO ,
r
fin
. 30
Th
. 00
II ^
.2 .21
,00
Ta
.3' 51
Sh.
.1 .13
I\ 3
/if-; .o
Th
O'O
?h
as
:.H_ .... -
h following the sewplo letter indicates that it has h*¡ heated; s fl'l-
iewias Vaa oasrtle indicates that r; v.*cs soaked hut act ostc; t> I'tr.ev wi th ao
h or £ iollcx.ina it is at urbanled and ursoaked control. The, troreudors ci.t.Tarunc
it. .Sj.y.ht after Tour days in the i serio.' tty he because i~ is jato oaloaroous.
3_'t is ell moult to scccnr.t Toe this oncLit ly raises an error '..as eogc in
the- origr'-itl ueiaht.


Figure 19.Specimens from the University of Florida
Collections Showing Dull Areas Not Flaked Subsequent to Thermal
Alteration Surrounded by Extreme Vitreousness in Areas that Have
Been Flaked after Alteration.


8
Hoi-v.es (.19.19 J649) quotes accounts of the Dip_ er
Indians on the eastern sj.de o.i the Sac lamento id ver end of
the Seri Indiana of western Sonora, Mexico, who employed
essentially the same technique. It would appear that these
methods were r.ot actually observed by the recorders*
Ellis (.19^ 0 a: 42) f urn i s h 0 s o t h 0 r e c ours t o p e r t ai: ;
to the Athabascan use of this method and describes several
experiments where "chippiny11 in this v;ay vas attempted in
order to settle the question as to whether dripping water
to remove I abes ir> fact or injch/' Fe says;
Expert'aentel attempts to duplicate ihis fracturing
techniov.s have shown it to be Tory unsatisfactory. I >
the 15 rst p21ce .f .1 int e:cr>oseo to an op.3r. f 1 a2:ic f 0r 0 ven
a shore lanrth. of time will heat through and shatter
into angular frayi-v r-ts and tiny f? mhos. The port!one
of the f 1 int v;hi0'.1 Jo j:nt 7he t1or n.-.y b0 treated ^rj h
cold wavei dropped from the end of a stink or by e ther
means \nxu little reaction, The usual result of the
application of cold water to hot flint it; the boil inp
an cl sc *ip i c! o ; r. ra t i on o f the d r op 0 of voter, Occasion -
ally snail chips may fly off, but their- direction and
position cannot- be ecutro?1e a, Dropping thorour hiy
heated flint info r r-on cf c o.i d vai e r will simply re*
rovc tin;y frarr 0: is vbich s~'e orclr.jo array by the sudden
chaire in temperature, but often ethis treatment
na 3 no y?, five results Also the flint which her beer
era3eo tod to f i .10 i.0 sc i. 11 ed \;i i h tifiy ire crno':0
and the cur f? o e s o f the mate ric 0 0 ron;;b.ened ci u a to
t b c d 3. i fe r- c-.n rial or pun si or. o f ch 0 c rye t of e c an no d by
t h o he a f j. j. iy, vita fc e j s : np o ? s i. 01 is f o uae 51 to an y
pro c hi r a .1 a 1 /an t a p 0 : :o th s h api np; u f c f one applet. > eivf a,
An examination of rheuranoo of sceeis. 12ns in the inusetun
f a i 1 d t c in d i c a f e i. I\ at fire p ami ufnct u -o (kj. i s 1 f' -0.'; t f ) *
ror.: : (1 v : 0 : 2p ) ace or ni iin c on pie c o arreo men t
with, ill is.
joi ou.t i/hich is do so rib,-1
that Vvs conducted prior, v-e
a 1 rv: s r o i Jen fie el-
1 -
3 n f ¡e o r: 0 t;i .,r -1c
'L kiiCv'lo jpe of i {..!.' c f


94
MASON, OTIS T.
1887 The Hay Collection from Hupa Reservation. Annual
Report of the Smithsonian Institution, for the
years 1886-7 pp. 205-39 "Washington.
1895 The Origins of Invention. M.I.T. Press, Cambridge.
MERCER, H. C.
1894 Indian Jasper Mines in the Lehigh Hills. American
Anthropologist, Vol. 7 pp. 80-92. Washington.
MUNSELL, A. H.
1946 A Color Notation. Tenth Edition. MunselX Color
Co., Baltimore.
NEVIN, CHARLES M.
1942 Principles of Structural Geology. Third Edition.
John Wiley and Sons, Inc., London.
OAKLEY, KENNETH P.
1955 Eire as Palaeolithic Tool and Weapon. Proceedings
of the Prehistoric Society, Yol. 21. London.
PETTIJOHN, F. J.
1949 Sedimentary Rocks. Harper and Brothers Publishers,
New York.
POND, ALONZO W.
95O Primitive Methods of Working Stone: Based on
Experiments of Halvor L. Skavlem. Logan Museum
Bulletin. No. 3 Beloit.
POWERS, STEPHEN
1877 Tribes of California. Contributions to North
American Ethnology, VolT^yT'ChapteF^I, p. 04.
Washington.
PRESSLER, E. E. AND W. L. SHEARER
1926 Properties of Potters' Flints and Their Effects
in White Ware Bodies. Bureau of Standards
Technologic Papers, No. 310, Vol. 0, pp. 289-515
Washington.
PRESTON, F. W.
1926 A Study of the Rupture of Glass. Society of Glass
Technology Journal, Vol. 10, pp. 234~6^7lKieff ield,
England.
REICHMUTH, D. R.
1963 Correlations of Force-Displacement Data with
Physical Properties of Rock for Percussive Drilling
Systems. Proceedings of the Fifth Symposium of Study
on Rock Mechanics, p. 33 The Macmillan Company,
New York.


4
resembles artifactual remains, and (5) tests demonstrating
that thermally altered siliceous materials are easier to
flake.,
3. To suggest a technique which might be employed
by archaeologists to determine if the chipped stone remains
recovered from archaeological sites had been thermally
altered. This presupposes that the alteration is a permanent
one readily ascertained by subjecting the material to some
sort of standard test. This problem is discussed in the
section on Archaeological Application.


e on cl" vi o t
I i u h J. ?. tec vi c 1 t ; y
Ail t/. : . i; i t: n "
re vu 3 t;'.. t a ; ob A.>.. : . t
J) i :j :i kc l 1t11* V:.. r,;, *
a Re £ 1 fi'c r i'1 V i r . , o r t:
ilfio, The c-ito v
0 ic at ir,; t ir a t iv: y co i. y t '
are not pror t v.;her roche ?':
t b o vyh the coro ho i e. c- j f r: . c 1 v. r c
is evident.
' hri.
-TU.ViV m..
2f. o c \ 2'0 - .
t- ¡'re ...c
V)j i:v
. i "C*" 0 Vi T O
l: ; icoo:' f11 nrc riv j. c
i-<. To reoowor-b a tschn:: or c v:.... ; i vt ' . *_-v >loy
by a r c ar. o i op 1 r. t a t o de t- o rv Ai e v;h c t '.or h \ o o' *? \ -' o h _ f
re. .a in a r e c ovo re f ro¡.i 11 -> ; o c b s c- a !. he r' :1 y j t: o .
!o prac t ic r I a te riu -= I'i :i v e:: r> t v:a ~ d ic. c ovt r? c Ho: v or,
.1 r ov. ri j c:?.t ~ r v o; n r ? . r c ; c t v1: l1' o p a;: r - o V \ "> h i r:
Cebrir % ?n inv v^ ti^otor r-.ould. fine, a vur.o:-j cf ccir.i a
e v:' ib i L i i j a re lie t u y 3 or-e a r ur rcui : o d h.y a re o s r.> -' h j.
.'l uG tor. j;1 a i o e i tu-.. I :.L 02 tren r_.? y sup:; 0 a t e t h :j >.; t i '.1 'I
are a h *. r not b s cf ? akd o ubre >yt on t t o he o v :¡ y *"h 11110
th. vi t r 0 v s .'i o !>^ e b c c . id. 2. te .
T: :p. ;t u: : c f ;;^'s-J-;.CC0 b 2 e : t f.'T2 zU.r L; tc 2; 110
i'3 cr ? c1-: ehe5 ¡ t >u v x- : t.y d 1 f 3?r: c t i <:r ; :.! err.ty - fcr
; a-. t 11 \j c' \ t- e ir b ho c ry:: b 11 1. o t lio 5 o c o ero. T j :h ,c
borna 1 o' t :>y ; v t .vr p2 y Mr: c a" vv t - : Lch A ,o\: 1J r.: c:b r ~-
in tbv- eht.-Oj ; 02' c-j i cr *:?. in on c,i' t: o ;:verve y.o-b .
The ''.Ite"-it: ' : -c dr r-t t iov: t!y ?rv ic :o.
i" ovi'v- uf . ?. 2 -.-...-/i d a:> t


81
unheated
heated
Figure 18.Surface Topography of Unheated
and Heated Silicified Coral from Florida as Viewed
by the Scanning Electron Microscope (Scale: 1 inch =
20,320 X).




m
Vitrc ou k . may not be cc-ipt. 1 e t e 1 y re 1 iab 1 e liouever
Several broken speci.ions were selected from procer aimc
levels (>2000 BC) of a site (a-556) in Florida. These
specimens ;;erc chosen because their outer surfaces v;ere
extremely lustrous and sore exhibited, a pinkish cast. It
v;s s su z p acted t ha t o 11 h id \) e e n th e rrn a 11 :y a .1 to rod Sna 11
f 1 ?l:es v:cre pre c = \ i rom e ac!i spec: men = O/ie suecir.&n v:hich
had an orpeci.' lly qrcusy luster on its outer surface v.r&c
very difficult to flake and the freshly flaked surface
v:as dul 1 T*ii s was a Cm s ampoin t inp do- el cor e a t bee ause
3t vms hoped that by rem.ovinq chips from field specimens -
it rn.qht be determined that vitrification which penetrated
the entire .¡ass of test materials is a permanent change and
miaht be useful for archaeological irtenpr&taticn especial],
if 1 oc ai out c r op mat or i a 1 s are no t n a t ural 1 y vif r->j o is. ?hi
cr G(i ri : en ha d e i the r p a t in at e d s ub s e qu e r-1 to t he mu 1 alter i-
tier, resulting in a replacement of the internal Punter, or
soil conditions due to lens burial had operated to form the
queasy luster on be cuter surface* fue former etvlrnat.' or
i r¡ .v/.v pi:? us idle b o o a if u- often materials t ha t- are n o t
1 u pt ro o c oi31 b a recoce rod fron tk.o r.ame 1 oc a tion as
lus t rob s : t ri a Is. I f soil c on i i i on s we r e re sp on s ibl e
f or tur 1 u s ter, th ?n s 11 s re c i me n:: s h o ul d b e affected.
J *i o mm in in ...n o re pro s onto L i ve sun r 1 e o f f 1 at ing
aobr:i o oj- arti rac L.s hut arv suspac 1 cd of Crinr al tercel,
an 1 fiv ?s1'i ;;ator s^ou 1 o f j nd a nuruber of soocirenc vhich
exhibit r. relict dull are a surrounded by cyi.ro me vitreous-
nT:is sitvr.ti ::i sv pesto tint Me
dull area bus not


&9
were heated te 3dcb ad 550^0 1 cft. for hours, -a t u
removed immediately from t.he oven.
The recults of these tests oro given in Table 10.
jin all soil; les obsidian for which the ceta '..'ere not
consistent.. there is an increasing relection in strength
with increase in temperature. In addition, the ugh admittedly
the data ere scant, there is an even croc; or increase in
reduction n strength vdisn nested s ...raale a are removed
:mediately from the hot oven.
If a comparison is mode between the results obtained
for compreauive tests tilth tiiose for point tensile, a dis
crepancy secos to exist. Under compressive strength when
samples are allowed to cool in the oven they resist failure
longer than unhemtod controls. The results of point ten
sile tents, however, revealed a sicnifi-i'-nt reduction iu the
time and lead necessary for failure to occur in heated saira'-l-K
resai'dlese of whether they were removed iron. the oven while
hot or allowed, to cool in the overo, -Thus seeming paradox
is easily :lair.od. The binding of the mic.vocryotals which
occurs; varea the roc;-: in heated adds coryresolve strength
threw/'' of; 'f;ion to ade strre fare Th.r, i a: a xa, a'- ir. hon.o-
.VCiilty which increase-', strength under compression is the
very factor .)ich daw creases, point tensile strength: (1) the
iridie id rel vicr-oc ry.atclr me bound none fir.-fy together;
(2; fuer.'feu-; wheel the flaw is J.str-.uuee J which is r.re-
3 is.i" ary to ana neceesary for- .fracto . io occur; (a) failure
tokos I-seo ¡-ic.ro readily bee.use the reaciien fr-Ctures neis
*! i''w w: th.r a e i -gy wy;-, Ti r:..1 dccre ac in


Figure 19.Specimens from the University of Florida
Collections Showing Dull Areas Hot Flaked Subsequent to Thermal
Alteration Surrounded by Extreme Vitreousness in Areas that Have
Been Flaked after Alteration.


27
TABLE 2
HEATING EXPERIMENT TO DETERMINE WEIGHT LOSS OF SAMPLES
FROM DIFFERENT LOCATIONS-

iH
Percentage Weight Loss
&
cO
W
100C
58 hr
150C
40 hr
200 C
28 hr
250C
22 hr
300 C
16 hr
350c
8 hr*>
400 C
9 hr
450 C
5 hr
500 C
4 hr
Total
Ahl
1.08
.14
.05
.03
.05
.11
.15
.10
.15
1.86
Ah2
.67
.19
.11
.05
.03
.07
.13
.11
.11
1.47
Bh
.67
.04
.02
.02
.02
.14
.14
.16
.12
1.33
Chi
.38
.05
.02
.03
.02
.09
.11
.10
.11
.91
Ch2
.45
.02
.02
.02
.03
.10
.07
.13
.10
.94
Dh
.57
.03
.01
.00
.03
.08
.13
.10
.10
1.05
Ehl
.49
.01
.01
.00
.01
.06
.12
.09
.10
.89
Eh2
.38
.03
.02
.01
.00
.07
.10
.08
.06
.75
Eh3
.34
.02
.02
.03
.02
.03
.10
.09
.10
.75
Fhl
.51
.04
.04
.02
.01
.07
.16
.15
.12
1.12
Fh2
.42
.07
.05
.00
.02
.08
.15
.09
.13
1.01
Fh3
.49
.02
.03
.01
.03
.05
c
.13
.10

Gh
.86
.03
.04
.03
.06
.10
.16
.12
.10
1.50
Hhl
.92
.00
.04
.02
.00
.12
.15
.19
.18
1.62
Hh2
.63
,06
.03
.00
.01
.08
.12
.15
.14
1.22
Ih
.60
.09
.04
.06
.10
.14
.12
.19
.08
1.42
Khl
.64
.03
.01
.01
.01
.04
.17
.13
.13
1.17
Kh2
.64
.04
.02
.01
.03
.08
.18
.16
.12
1.28
Mh
.77
.08
.07
.05
.00
.09
.17
.16
.10
1.49
Nhl
.49
.03
.03
.02
.02
.08
.13
.09
.15
1.04
Nh2
.35
.02
.03
.02
.01
.06
.13
.08
.14
.84
Nh3
.40
.04
.02
.03
.00
.09
.14
.13
.12
.97
Nh4
.44
.03
.03
.02
.03
.07
.15
.08
.11
.96
Ph
.71
.15
.07
.03
.11
.11
.15
.13
.12
1.58
Sh
.14
.04
.03
.01
.02
.00
.00
.00
.00
.24
Thl
.88
.08
.05
.01
.02
.09
.15
.18
.11
1.57
Th2
.85
.05
.06
.01
.02
.10
.17
.17
.15
1.58
aSamples A and P are silicified coral; samples B, C, and
E are cherts from High Springs, Florida; S is English flint; all
other samples were obtained from differing locations such as
Johnson Lake in Levy County, three miles north of Ocala in
Marion County, and from Alachua County. All of these samples were
heated twice at the same temperature but the results were com
bined because the second heating produced no significant addi
tional weight loss. It should be pointed out that if the total
period of heating at 450C had been for a longer duration per
haps there would have been less weight Xtiss at 500C and thus
would have resembled more nearly the results of Table 1.
^These samples were heated for a total of 12 hours but
the results of the second test of 4 hours were not reliable.
cThis sample
fractured at 400C.


TABLE 7
RESULTS OF ATOMIC ABSORPTION SPECTROPHOTOMETER ANALYSIS
Sample
Percentage
Mg
Fe
Ca
P
Mn
K
Johnson Lake
(fine grained)
.010
.250
.033
.003
.015
.040
Johnson Lake
(coarse grained)
.008
.400
.045
.016
.010
.020
High Springs
.011
.1115
.095
.035
.010
.042
Ocala
.040
.290
6.600
.040
.025
.050


ri .-
.11 o the experiment:;
1 ; v u U'j 0
id unhoaicb spocineus but it
.-'i I.:-" O'... ',; t
j x o c i. a X coto / o xrj a a : c x 5 b in g r;
. xxxr ai. v o. ii-
riici \.;v!ion the me?: noterial3
''uee-z tr*a "> i'c 13 o d v.1 j b m 1 'Jh.
: t o e c. s i£ -eb : x: j e: -
nrjr so ¡ _. c e sliiC'i mo n '.'a i ;j
oi ore exn i . : ..
.. icti- ¡X c t ?: e n c- d f or anc t X.c r ;
in J. c h i n r u m s u. .e e _ z t i 11
oiX'x-.r.M, Apointed out in ih
lo.tero .Aire ii;\> X- x.jly
C rab 1.1 can Bu ti e r? & (19 b-!-) art! a j o c l .1 e c u s *.? c? r;. : ¡ :x¡ ino 1'
r>i.l:. coous Materials iron an archaeoj opio all;? £.:i '-1. fi.canb
po:L*jt of vicvj therefore* the?vs nix c.-' a pior ;-
1* j r: nntuie.
;cir:ht icen
Tv; a 1 v a 1 in c h c ub es, a e 1 v;o 1 -hir 5 ; ? ;r j r1 :* i a ;, c: .,
i?. f.;r?: a-;c re 1 ub oriouslv or:*0x00 t0 l uec / f 0 r -r ll-
i-r" g ': ' .: at.i'nr.Tbi'- tecta* (do 0 headin'; entitled ~'V
i i. f0 1: ; bc' cr.i 0ti0n an<1 reculte of t'is cxx ;: x
; > r ? .e ean; l1 : r; \. e ; e t:;; .
:c:c i:< f'oiloi.'C. j\.o
i; .> oa of ev.- i.di *; i :i .:
tied ::' ' 'Uii i : ul-.t chert
:'i: \ o j. ,i ;oii *. > -. t v' :. J e t i'
,.; 11.::i nov* c / ..i a
3<*i ! 1 {.jt : v.
f-j.:rn..9^HKo
j '-x ;' 1; ::': } z-V.e o ^ x 1 no '* l in o 0 ? c :> t c. : 1 ; ho 0 f ¡1 ' V'. t;- -! 2 r V u ';v X,/ c 00 1- \ .?ho _/ c i;: a . > ?i a t <_
1', >s; C't .. r. .
r vb i;c.'l.:.'tdeten,i-/-, if
Ti v,\r:: V..,!,ld h -
-j.x;i at K-J h X h
dno ', U )e-A
. t i ill ;:


14.X-Ray Diffraction Pattern Illustrating that No
Change Occurs in the Crystal Lattioe when Florida
Cherts Are Subjected to Critical Temperatures ... 72
15. Results of Differential Thermal Analysis 74-
16. Petrographic Sections Showing No Detectable Change
in Heated vs Unheated Florida Chert ........ 77
17. Surface Topography of Unheated and Heated Johnson
Lake Chert Samples as Viewed by the Scanning
Electron Microscope ..... ... 80
18. Surface Topography of Unheated and Heated Silicified
Coral from Florida as Viewed by the Scanning
Electron Microscope 81
19.Specimens from the University of Florida Collections
Showing Dull Areas Not Flaked Subsequent to Thermal
Alteration Surrounded by Extreme Vitreousness in
Areas that Have Been Flaked after Alteration ... 86
vii


62
samples of Ocala chert, 1 inch in length, were prepared
One of these was heated to 400C and the other was kept
as an unheated control. Both cubed and cored heated sam
ples had been removed from the oven immediately at the end
of the heating period without first being allowed to cool.
The significance of this procedure will become apparent
later.
Arrangements were made with the Civil Engineering
Department at the University of Florida to test the strength
of these materials. The equipment used was a JOO,000-lb
capacity Riehle Universal testing machine with hydraulic
type loading and five ranges. The results are given in
Table 8. The cross sectional area of the cored samples was
standardized to 1 inch as follows:
2
A = nr
A = .785
The figures resulting from the compressive strength tests
for the cored samples were then divided by .785 thus ex
pressing the force in pounds of pressure per square inch.
In another test, cored samples of obsidian and High
Springs chert were prepared for compressive strength tests
as described above. One sample of each of these materials
was heated to 400C and allowed to cool in the oven. One
sample of each was retained as an unheated control. The
results are given in Table 9. See Figure 12 which graphic
ally illustrates the data presented in Tables 8 and 9.
The compressive tests yielded the following results.
From the data given in Table 8, it is apparent that when


Investigations Concerning the Thermal Alteration
of Silica Minerals: An Archaeological Approach
By
BARBARA ANN PURDY
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OP
THE UNIVERSITY OP FLORIDA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OP
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1971


33
2 O i-ulS i.. had i ti to v5)c' for
?>\ hours viere re.ic. e. from the ov'Ui with tora! while hot
(still 35CC); tho tonas viere warmed on the side of the
over, before touchier the hot stone, One of theta soapier
snncpe.i in half with & n.i'j loud sound (roo... t o.aparsi live
v;: about 73" Cold voter (hee water) a ; cirio; ah sle::_.
the edge of the sa;rales. with a dental e.yeeln. e to see If
they would flakethey aid not; (Sec literature Ievlev: for
accounts describing this alleged phenomenon. ) Tiiv- a erre leo
were then placed directly under the tar. and cold water
allowed to flow over the entire samp-lo. Shis resulted in
an audible hissing sound and erucing o the nateri.E.1. She
came procedure was followed with two samples idiot had been
left at 4C0C for an ndd.itienai; 6 houis, Gassing ooouurod.
and subsequent attempts to flake the meiu'-iel cr.uc-rd it to
enable, It was impossible to i ressure flair, this vaha
r o.l because tho flakes could not bo removed in a r-re-
djct:at-5o ..'ey. 2!x specimen literally fell apart (seo
Fail.:.' aurr.cd p a ah tar by irropvlur crack:
dihih ar v ; in egj. .r_.-a:o .h e:.. ; 1: carcho: dal
fa. chura . (Iresslor and Ghoaitr 19rh;: r'h.l).
Ctbcr : .. rb.a.v:' wore conducted to tost -la
siy-vi fic 'nce c.f the <; vac/.ling sound which oc corre: viven
spec;icnt ware rneovoi ir/oGiatcly frou a hot oven, lese
expo!':'a.-../.;..; ..ill be discusaed at live end. ol' this section
and :a those a lir, wi til fcjiaraftic Aval, so la, aid btrength
TfOtW:,


LIST OF TABLES
1. Heating Experiment to Determine Weight Loss of
1-Inch Cubes 25
2. Heating Experiment to Determine Weight Loss of
Samples from Different Locations 27
3. Results of Experiment Conducted to Determine
Ability of Heated Rock Samples to Take On
Moisture . 50
4. Heating Experiment Conducted to Determine
Differences in Heated and Unheated Specimens
After Soaking for One Month 32
5. Heating Experiment Conducted to Determine Weight
Loss of Archaeological Specimens Suspected of
Having Been Thermally Altered ... 35
6. Heat Soaking Experiment Conducted to Ascertain
Length of Time Necessary to Effect Thermal
Alteration 42
7. Results of Atomic Absorption Spectrophotometer
Analysis .......... 55
8. Results of Compressive Strength Tests When
Heated Specimens Are Subjected to a Cool
Environment While Still Hot 63
9. Results of Compressive Strength Tests When Heated
Specimens Are Allowed to Cool in the Oven .... 63
10. Results of Point Tensile Strength Tests 70
v


I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
Charles H. Fairbanks, Chairan
Professor of Anthropology
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
William R. Bullard, Jr/
Associate Curator, Florida State Museum
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
Harold K. Brooks
Associate Professor of Geology


3^
*r-
b hr
R U 5 1 1 4 2.


IATjSKIAjljS
The terms chert ar d lint h:x\ e V c on u ,3c d i n der-
c hange a o 1 y and it s d 1 f fie u it te d o t n ¡ en o f r on t he .1 it c ra -
ture if any actual structural differences exist betv.ee. the-.;-.
Flint is a teriii widely used both as a synonym for chert
and for a subvariety of that material. Tarr says that
flint is identical with chert in texture and composi
tion and the term} therefore, should be dropped or re--
s eeve d f or art i f c.c t e (I'e 11 i j ohn ] 9f 9; '?fC).
Thus 5 in be seribing chi jpf. u s t.one t o ol s, onmi gh t s ay, f o v
nxuiiple. that f 1 inb arciiacts v;ere marru¡:ctured of ,;j:*;i:aoga>.
n ov ao ai i t o, r e nn n y 1 v ana jar. r e r, etc. This is, of o or ire,
ai re ady being done to a acrta in exton t ai - te those in t-v. -
e at e C it i 1 it hie techno! o gy in ferns t i on o f t h 5 s n.a 1. ure .¡. s
1 m no i11 an f since it c on 1rib u t ec- ?;re a 13 y t o i un .3 e r s t an c. 1 r g
of the bind of v/c item an shin that might be expected or whothe?1
trade re3 a11 oi>sb ps c;n si- rd i f the Le via 1 is i#ot 1 ocal *
I'O £ t e.j abac o3. og :l ? t s v;o u 1 d d c f 3 ne iM in t r a a noc : o : :n -
pocad cf micro:rystall?ne quart/, that br.._'.s vn Lb a conchoid ad
f ivm tu.re. j:h.i e rs an adoqua l; r";?ne vo.\ d a sc r in ion, biit do ?
not su f io n . at n spec i f ic a ter 3. nl s fro; i d iv i r go ogy v:; -ic
areas are being considered- ''ron the ¡stru.p clef of this in
vest tget;i on, Vno;;1 edge o f the ic mo fc iov and com;>osit vi of
slice ou s 7at e ri a3. s n11. :i vc t <. t o s t c 1 e o f 11 or id a i s no c o s
sag.' ?.l\cc ' 11erction bvr r; r ?. 1 vt ret tm? o C' 1 ace at the soro
t c-r; ivjaf; i r. :i: ! r:t e 1 s '..l.oc: l-vc. tre :! s s31: bf 1 y c? 1 ff ci%-i11L.
13


60
time consuming, a coring device v/a. used which greatly rodecod
the time needed, to prepare samples. Using a drill press as
a basic place of nacbinary (Pi? uro 11c), a Coronatic diamond
core bit having tui inside diameter' of 1 inch ,005 with a
6inch core barrel and 5/8-inch diamond penetration was con
structed by Anton omit and Cc., Inc, New Yorh* This is a
variation of a Coronatic drill used to cut holes in glass.
The chert nodule to be cored was clamped into position as
ilinetrated in Pi g nr e lib.
The diameter of these cored samples was exactly ovo
inch. The- cored samples that rere to bo need for compres#
sive tests wore then sawed as close to one inch in lenet-h
as possible and ground to precisely one inch. This reduced
the number of surfaces to be ground from six for the cubed
samples to two for the cored samples. The cored samples
that were to be used for point tensile strength needed no
addition si preparation.
Comoro ns iv^ Tests
Of the or i g in al tv o 1 ve 1 ii te h c v.b o s, s i x v;e re he a t o <3
to 500 0 as described jn the section on Keating JAcperimen ts
and ;-!>: were Kept as unboated control.:;. One sarjle each of
ho>t:-d and whin bod obsidian, ailiorvieO. cord, and chert
f ro. a quor ry 5 '*i2 es north of Oc r; 1 a -were used for compres-
civi- tost* Compres?; ivo sursr.gtb dote obtained. from the
cubed, samples cf Ocala chert were uiu.*;.liable due to error
in b es ting; t j ip t. e \¡ o r e d i s c a r da d. C u b a e g u e a 11 y t \ /o c o re u
^ To 5 den t-i i y l hi c mater r* ,> a as ta 1 ooation i v vi 11
he re after b e c a ]. o a Oc i a oh r t,


?'!
1- HA, OSI ff
1887 The Tjj Collection frw lapa VTSorvatict,. u a_.l
te-orT c.T the Srilh'-oisiati Institution, for thd
yeans I te-'/, pe. 80p-;;j, l/aoainjpfcon.
1095 The Origins of Invention, i",.,i,1?, frase, Cambridge.
rSiSi;, h. c.
l-l Indian Aaspar ¡lirios in to, j. sM pe lir Aner?.c nr>
:l£SiS2E.2SBS> Vol. ?, ijj, 80-92. Washington.
KlJKihl'M a. n.
fw A Color dotation. Tenth Sdition. ¡¡.ESll Col or
co., Baltimore.
he-/...'1 i, Lhc.e.c. a! I:.
19'l2 Irlncl-iles of Structure]. Gcol-'Vy, Third edition,
Joim V/ .Ley and cene. In o,,'London.
OEOT, 'JlEihiEi JK
1955 Tire as f .d acolithic Sen;] and. oapon Troce coi ¡es
of the TrjiilotPric Society, Yol 21. London.
TLiTIeOft.,, f, 0.
19-T-9 fen-d?.3-g-tB'.y 'ojgtS KjWfe* 3r others; i'nolicpprc,
Lew York 7
TCKJD. AlCXCO y
1950 fricitlve Ltiiods of Verkin;'; Stone: Based en
¡experimento o halve r I,. feeder Loen ¡p
Bulletin, Lo. J. Baloit.
whites, i'Xtviiy
1877 Tribes o California, Conv-ri'oufcioris to- Horth
gorjean Efcl oology. Yol. 3", UbaiitorTl, 1C':.
Washington.
mi, d S. H53 W. I. SKEAlKk
192 Properties o otters' Hints and Their effects
in Whits U ore Bodrios, Bure pc of Standards
Technologic 1 surer;.,, Kb. 5.157' foT. 20, pc. 229-315.
v/asiii.npp'jon.
J.'n LiA'i 7 ? n. ,
J 920 A study of the dr.'turo of Glass. Society of Glass
OteciinelotiY Tour-u.!, Vol. 10, ;r. oheffiel.I
Scpf esc.
kCEOdhUrh, b. x.
1905 Correlations of fcrse-Sio.-lacce-enil Tate with
Tkysieal Tru-ortios of hoc;: for Lv-reuesive drillin';
System. Tr-orv'cclinm of the fifth Gyr.noC' pc of Gtu
on. hoc Qcl a f Ti 1^0 Clii P'l 5oC c P ,
he. Yorh.


altered. The number wight l?>. L increesod ; f; wore
kn own vrhe the r pa t ina %o <1 s pe c iv :v: o r cp c ii:.ens j-e c o vx e d
ix'cm under the water had bee73 subjected to boat* Patinacin
as veil if minrala ira rent in Ploride lakes. rivers, end
spring . c ai': t- o o h a ?re e s > h: ch c o; e o n I a ho c r iy in el to >: t u r o o f
chert a iking it incoariblc bo cetorrire (at preront) if
then.; a 1 al to ration has token p *
The objectives or the ;c e rch them under t or< "i
were:
i To establish whether a fore Mee;;}.} y desirable
change in the chert occux's wi-on it is thorrally filtered.
The e rye r !:; e u t s cor. doc to cl ar e c! e s c , x y o:: i r t h s c e c t i on on
methodology which embodies xhe p:ajor portion of this dis
sertation *
2 To demonstrate whether prehistoric pcelo:. night
hav e bee n a ware of t he £ civ ant t r; c-s c on fe r re d by t .V e in n ] ] y
liter inn their lit hie materiel c. To aid in this endeavor,
PE :* r t n a ivc snd o:;t ar: ? I x e ? o a}1 c of s x:*.: 11 r y pub 1;. c at x cr .=.
was cedcrtaMrii The xv suits of this search arc described
in th*"1 Literebore hev.lev;,
Th.;. 1 <.%e o V a;t 1 *>yy ir 3 r te r-pr;: I; i.o r archae oX oric a 1
dr-ifcr- *Jln it.?, nosfc ¡je* ...val cenec , sea;,piny any belief
ubout non cb?. oxvad bchrr-'*! or ry r c torre 1 t o ohsor vec behavi cr
which i tnoayht to bo :;: lo'.ror;x" (Aecho r 1SG1: 517) Un-
TortU'cte ly, >; c bc-ri c accomits vcrc not f our-d whic 1 j acc;ux ^tc-1 y
:e p:coc o :> of tlC rr;.c l f111erat i on Ho;;e v s r, en ou.r, h
de script ions of the use of fire cnirirc; so no stage of etc; no
tool :nufac turc \.cx c .;nco*.-: d to *.;?... vant eke coccivai cn


Endothermic
Figure 15.-Results of Differential Thermal Analysis


Abfetract i. ux.i -'i:' ti. a n.". fe .. d o jr Cour.oAl
o f ti: e l j i v..; 'i A ti or ex i i are, j : i' ul A i 1.1. vb of L:5 m .
iec¡vr Gs fet- tVio 13yro. ov Doctor of I:>hi 1 o\>hy
IK'/lTlCT.-'.DJfi! i CO-'Go.-di"C .ihldjihi; IL L^-o.u"
Or lJjIO-t ? .Xl'iJii-' LO : Al i i HCn UvC'.CG 1C; L /IriaO, C;¡
By
Do rh c r o A; \n IA : rA /
h^reb.. i;"!
C ho i. i-i.- on: Oh a r-1 es i ta i rb arb. a
I Lo j or De y t.ol t: Ari fc h i*op o 1 o
A recent publication (Ovv:ht.rv / o. -.i Duller )
Uojifctc-. that prehistoric Lien may h.-.v? ft'.uno it ed/ante:;;: ~
ous to thermally alter lithic io:: rcvr/A.ln pe :>j. te we--
f a c t ur e or t in a 1 o c r-p 1 o t i on of chi r p r: v t n o t.-j j, no n i :,
The s pe o i.tic o b o c t i v c k o i* t! : -j i. o:: o; j r c h i.\ t he
c or c ?. u*j i or, fe r o a c hed ar-e s. c lo 11 ova :
1. T c c s t a u 11 £ h v. he ti; v r f un a t i or. A, y i. o o 1 r ? e i
chrir.e in oh,;rt occur ; .;nrn it ir ru io : i uj v'e:,t. Ah:-
ryj r i no n t a v e r o c er. .1 u c t s d t o d e A e v .ir.; A Lo v >r r a tura en o
1 en;. 1 h o f t i m- n c c o a : a r.) t o effect t q de t o c i sh ; iv re,v i
a 1A or c i i o n :?. lio / : i. an:! un he a i. o Z til. o r i o -i. c h c- j tr re re 1.1 si
;; y p e t r o a: v.. yh- i o r. r i y r :¡r; y d i f ir a c G i c di i ib: e r. t :1 I
t'' / rri -1 -ve v. 1 y n r a c e a .h p o 1;. c v ce n :. i :;o o ^e te: :.l c
r ] oc f..;. ior: t er ar:.. .1 yr i ;* 5 &t :r: dare vo j; .n ch .ic o. r t ,f
r . 'i t re v. : i.:, ct i er > o ur f r - j. ¡ p a r o o i t y te o h n i q u
c. a f..¡ ci e ve //.! i*i Vj, i e r prL ^ i. u u _ j \ 1. e: "i i1 in v
1! vh o- v.n n: r- r ; o J1 c h *' nd.v:c-'11 a;: c- c or. li.rr . hy t r . e /; -a 1 ?. j
a 1 i o r J''-;; j i 1 h lc i j. A.' _ i s 1 :->, ji. to v i o >: e f t! . ; 1 i ; i, v r o
i*'' ¡ e i' . A n ^ >: o. .1 '1;/ i o e r. v. a o c*: ¡ r \c : i:. i
A A


72
Figure 14.X-Ray Diffraction Pattern Illustrating
that No Change Occurs in the Crystal Lattice when Florida
Cherts Are Subjected to Critical Temperatures.


9
Schumacher reports that
The rock is first exposed to fire, and, after a
thorough heating, rapidly cooled off, when it flakes
readily into sherds of different sizes under well
directed blows at its cleavage (1877: 547).
Powers records the following:
It was a source of wonder to me how the delicate
arrow-heads used on war-arrows with their long thin
points could be made without breaking them to pieces*
The Viard CWiyot] of northern California proceed in
the following manner: Taking a piece of jasper, chert,
obsidian, or common flint which breaks sharp-cornered
and with a conchoidal fracture, they heat it in the
fire and then cool it slowly, which splits it in
flakes (1877: 104).
Other authors (e.g., Mason 1887: 226; Fowke 1896:
172) refer to the Powers and Schumacher accounts but add
nothing pertinent. The methods described by Powers and
Schumacher are more plausible than those avowing that arrow
heads are made by dripping cold water on hot stones; how
ever, it should be pointed out that they are in the minority.
The above references constitute the totality of the
available information on this subject with regard to American
Indian practices unless some undiscovered source exists.
The author is in frequent correspondence with Kenneth P.
Oakley of the British Museum, London. He was not aware of
this technique at all and could not "recall reading any
account of any people heating stone before finishing in
projectile-point form" (Oakley 1970, personal communication).
Another European scholar, Francois Bordes
. laughed until he tried heating some flint and
then he became convinced. He has now traced the
thermal treatment back to Solutrean [see Bordes 1968:
1593 and both he and Tixier have done extensive work
on experimental heat treating (Crabtree 1969, personal
communication).


42>
'O eitK .'50 0 or 400 C i ail cal;; , -.j a ik- - 7 ei t to.
u 1 ui..t 1*. o r s mre f or f h o o t,- '1 ::? d of t x e Th
c'Vi v#as Sint off end the cype\i r-o allowed i:o cool in the
cyy; . T u? gradual o; a s e t o v i t r.i float ion s e o us to g o h cud
in mi ui wIi or inoreas:: r..; v no in rerrev in:' flakes, If
afc'j w.s take p] \:o too rapid] y, dr^atic* dor in activo
ov-:'n te o e cur* Ir bhoa L 3. ko o:..! o o lot- d f ai; v i r'oo .- no e :.-
is not apparent unless the rook sycch.^i if. brol'.-.n
chi^iy after hcotin-.- The exterior surface of eke heated
Core xdifain.-j dull This is illustrated in Figuro 6o,
:tototo
T b o ini o X: i.; ; i c j i p r o o tXLtj to t i . i r> x/0 i .. c. h e be<
¡;;. i1.." / oV- S3 r v o t i o?i end d. e s c r in i: i on. Tn e d a t a no; re r ,;' n v ..
h c J.; it.:. va v ; c ;n i Ltc s 1/ n:<_ fie nr o o o i ce o :: p o *. it; >... t r d i -
cure- d t
I t so ex'.o air 1 :y c.1 e >,r that no roll :&/ o ii j fe r " o c v e
c i.-: ; :. c* fro n 0 ii o ¡? a: ¡ c c ^ in we i fb t I c v. e ;, n g a:. o i; o
h? : ; e > o e. A e:;:: o :=' a roh o o o] egie a I r o o c i ¡.'. nh r. v e c. ux-
thor: : 1V- ttred* kvr.n x-rder controlled cooditioT:;;,
t ? ! o c:. ". j fi o. ii. d t j V o r o: o e j \;; r* t ?. c ; c fox' 11 e n ~j-' e
J - v. r "at - e j. -.... e ia' :* vk 0 c >: : e i ? e : t o~.ept as
c i: 1, r o l M r-c p- ihi o *.r o c o r a d v. ken :1 h in p c on -
exto ir.-, V ^ ir.: c o r. C .If." -e r ¡. m fc r o v "xr- o r1 th e -.e r, ' o t o f
ee.eroo; e ,
] n e./: e L; .h ?= :.'.o .t c-t re-.t tv. o of't ct h : x*
t or ,n} -!/ .ifi.nxv.e- in ft- Ob opr c
o i ,y \ . v:; ;f; ?: ft l ;. c<-. i,u ofu.: I:...


XjXsj 0}y x...i _o
1. Heating jRaforir:out to Ecteruine might
l.-Incc Cubos . Hi ......... ?c
2. Butins ExsuriBfc De termino RcifRl Loss, n
Ratifies Bon Ri ffcrcnt focatioos .......... 2y
3. Resu.lt;: o eaearaasaoe V CoBuctco to Do Ovni o a
Ability 01 Heated Roer carrales te Caro Or:
hois tu ce ..................... :0
ijf Hd&t la rBHMr iut Conducts'.:, to Date.'! rao
Differences HKhatea and Unbeaten. ira'
Afta::' COdi:in-, for One Kon.t:: 52
¡y* Hea'fflr' Hxraerincut Conducted to saboree or fe: flu
a? ¡Bf Archr.eolojljal Jr-acinens ua;:ected of
Havin': Bonn fl.ercnf! i y lr-red .......... 5o
6. Heat ScaHino, rRtferi rent C'ld;uet:: te srid:
Lcacrfad o faaor TMbosury to Effect 5 anc.-l
Al te ratio ai 42
7. Results of Atonic Absorption e;r jca rof: re... a:
Analysis ..................... 55
8. Results Csf Corru.Bssivo .Jmv-uath 2- s. W or
^Hasted p|${¡C'J.-?-ls Are .fe.' S*f Casi
Divirorrant if lB:;e Hot ........... R5
9. recae ur of Cenare gijjjp ffeoiifta .a a Usaos Jested
Spcci;'..acKre Al BH i tti f se: 1 ac a tea: fa: : t i
10.iieaelB of foist fessilo dtranffi: Rosta ...... yO
V


56
Figure 9.Specimen Depicting Intentional
Fracture with Bulb of Percussion and Typical
Fractured Surface Emphasizing that Impact Has
Occurred.


45
the change was reached and maintained until the change
occurred. Obsidian (Table 1) lost no weight at all but
other tests suggest that a change might occur (see section
on Strength Tests). A quartz crystal and pulverized quartz
lost very little weight (after 24 hours at 350C they had
lost .01% and .04%, respectively), but it has been stated
that quartz becomes easier to flake (Crabtree, personal
communication; Man 1883: 380). English flint lost only
about .15% to .25% and, because it is fine grained, we
suspected that fine grained Florida cherts would lose little
weight and coarse grained Florida cherts would lose more.
However, there does not seem to be any significant, pre-
dictable difference between the amount of weight lost and
crystal size in Florida cherts. This could be due to
heterogeneities since even fine grained materials may have
large void spaces that cannot easily be detected. It is
more likely because, even though there is less water in
any given interstitial space when the crystals are small,
they are still anhedral and probably are not packed any
better than larger ones; therefore, the same amount of
water exists even though the crystals which it surrounds
differ in size. The difference in weight loss for English
flint compared to Florida chert might be due to the condi
tions under which they were formed. Florida cherts prob
ably contain more water vacuoles. The cryptocrystals of
English flint are probably more closely packed. The smaller
the size of the crystals, the greater the surface area
unless the crystals are intergrown.


C9
t. vas. Tl1.if. would b: almost as riciouj ovo a
3o,;i tb.i, 3 :ri no conception o tifie because he hadn't
ir.v .-uto-i tii watch. Besides, those investigations dernen-
Etr. tod that, at beaut lor Herida cherts, toaparatures
botvoan 5;i0C and 600 ¡3 (a ranee of appro..irately hOO'- i)
would effect a desirable alteration in tns material. That
is, as ?cn- as the elevation of temperature was gradual,
thc-ru was no iiicro :;sc*d case of chipping at £G':C over that
of 55CC. .fail a there is no apparent increase in flaking
ease, however, quite often attempts to chip flint materials
that had been heated to 5000-600C or bad been heated to
J5<., C-d-CO^G and removed immediately from the hot over,
resulted in. a lateral snap due to end shock. Thus, there
is additional strength loss with increased temperatures or
increased stress. This fact was supported by point tons:'?.
strength tests. Below J00C a satisfactory change did not
occur in Florida cherts, Materials were not tested above
600C (approximately liC'G!?) becaise the r>origines probably
could rot reach or sustain such hitch taiaperaturec.
It re.tairs to deten-in-: if the throe major problems
to bo ijiv':<-tigr.tod in this study heve been successfully
solve 1.
1. i -desirable- chuige doce occur when Florida cherts,
are fnav,!. 1. ¡slurred resulting in a stone that is easier to
flake than 3ts unheated counterpart. No structure] change
occurs in that the s5.se, share-, and orientati"n of the
individual sdcrocr.ut Is re- ai>. the s-u:--' liu.t tb.vr-v h r-
ui.o/al ... C i.n t.-r.tw,i a. 5b, :-i.r; a-., y-a vr i.


58
Figure 10.Heated Specimens and Dnheated
Controls Illustrating Degree of Color Change
Depending upon the Amount of Iron Present in the
Chert.


7
Exposure of Flint to Fire as an
"^AidTljr'the CElppiSg ~~Process
This category deals primarily with firsthand accounts
or, perhaps more accurately, fanciful interpretations of
firsthand accounts.
It seems appropriate to mention the following well-
known description which appears to have had its genesis with
Herman Lehmann:
Me threw a large flint stone, from two to six
feet in circumference, into the fire. After the
stone became very hot, small thin pieces would pop
off; we selected those pieces which would require
the least work to put into shape, and picked these
pieces up with a stick split at the end; while these
pieces were very hot, we dropped cold water on those
places we wished to thin down; the cold water caused
the spot touched to chip off, and in this way we made
some of the keenest pointed and sharpest arrows that
could be fashioned out of stone (Wallace and Hoebel
1952: 105).
Though widely accepted by laymen, the foregoing has
been largely discredited by most professionals. To those
who are sophisticated in the art of flintknapping, it does
seem like a waste of time to use this method even if one
could control the dripping of water sufficiently to predict
the type of flake that would be removed; the work would
proceed much faster by using a percussor or pressure tool.
Along this same line, Holmes (1919: 564) cites "A
remarkable account of the use of fire in chipping flint im
plements ... furnished by Thomas H. Fraser who
was informed by Chief Paul, the head of a remnant
of the Mic-mac tribe, resident on the northern coast
of Nova Scotia, that in his grandfathers time, flint
arrow-heads were made by the systematic application of
fire and water, and I still have in my possession an
arrow-head made according to the process described by
him.


50
load* In addition, while there is no apparent increase in
flaking ease, quite often attempts to chip flint materials
that had been heated to 500C-6Q0C or had been heated to
3500-400C and removed immediately from the hot oven, re
sulted in a lateral snap due to end shock. This fracture
did not occur at the point of impact. The fractured sur
face often resembles that illustrated in Figure 8, Flint-
knappers are familiar with this type of failure since it
occurs when a substantial blow is imparted to a rock whose
mass is not adequately supported to absorb the shock. With
these heated materials, however, failure occurred when only
slight pressure or percussion was applied.
The composition of the chemically bound water may
not be identical to water as we normally think of it, that
is HgO. If the hydrogen and oxygen ions are dissociated
and the oxygen plus part of the hydrogen are given off
when a certain temperature is reached, the remaining hydrogen
ion with its positive charge may hook up with the negatively
charged oxygen "skin" of the microcrystal and serve as the
binder. Or if the depressed silicon ion is agitated, it
may hook up with an oxygen ion from an adjoining microcrystal
and thus form the bond in that way.
Pressler and Shearer (1926) offer some suggestions
concerning the reactions of various types of flints when
heated. Their article is concerned primarily with flints
used in the ceramic industry but may hold some applicable
clues. Since temperatures of 1400C-1700C (>3000F) are


83
he did, lie voidh- to use the results very cautiously
since he could not be absolutely cure that his site .Material
was 5 dent o a 1 v; i t h the outer oy. ir.&t e r :i a 1 C h er t wi 11 v a ry
c ene id e rao 1 ,y e ve n .d L V-11- t he j aue n o dale 1; if fe.. e n t i o 1
thej*ma 1 analysis probably vould also reflect this tendency
of tic rateri ai to tife on roisture r
If shone 1*011.airs are found vrith ,:pohlib'! fractures
or fractures vinua bulbs of percussion, it mtyy be said that
the stone had been fractured due to expansion or contraction
re Sul tiny fr-ojn heat, but there uould be r.o sure way of
deter;dniiu. if the exposure to the heat had beer, intentional
o r boo au c e of o f o re e. t f i re o r he a r t h c i t ust i on,
Standard roclo inecherd co tests od^bt be of value to
t e s t s i t a o p e c i rae n s wit h o uto r op in a t o r 1 a 1c, but :i. t p rob ab 1 y
v/oo.ld bo impossible to recover lar ye enough specimens froix
sites to prepare samples whoso dijnenricui:: rust be precisely
a c c u x x g in o r de r t o e. s sure the v ai i d i t-y o x the reo ul t a
fi'hu fs this ¡no bh c d .sue c e e d 3 in t he o ry bu l \ i 1 s in practice. 1
application *
1 v oyr sph ic an a 1 ys 1 s r e v e s 1 o d r o c hany o i n t h e
size, e h Cj o r o r i en r t i on o f the in i i vidual vie roc ry s tais.
3'fc i v-1 nb o x:x o o u t by 1 h ; :c-r i y di f fr ac t ion pa 11 e rn wh i c h
'nov;c ) o e 1 ; inpc :>n tlie c ry s t a1 1 a11ic o b etocen heate d and
urf io a t c 1 in' t e ri a 1 s,
f. c vi tr v \: i-.so o f a unrfac r- uh a t Las b o on f 1 aleed
subneoucn t to th a 1tox*. t;1 on off ovc perila s, the or;t
valid i r cl i c t .1 : n it- t 1 his r c* i, > o d > i ao 1 > e c n cash o y o cl c


/!-
resonbles av1i f.¡ncua? :' e r.&insana ( p ) - s -3.
that the rae 11 y altere sil: o .v c v s r. e. t o r i al s a r e
.flake
y, To sujcs e s t a te oh-'. .1 ::v o w 1 I c h r. i ah L
bj are 1:aec 1 o-j 1 sts te 1 e ocr:s¡ir.-o i.i the or ij>/. rd
re cove re a rea archas o! or .te al si ce o had he en t
altered. This presue coses that the alterstier
e: :nstrat:Li
easier to
V-J non!o.vd
sta-no x-.¡ n
hor'ia" ly
|f ajer.a*t
one readily ancert _'ir.ed by subjectin'-; the rawrisi to ;:m, c
sort, of standard tent. This problem in ojnousnod In tbe
section on Archaeological Application.


METHODOLOGY
The experiments described in this section were con
ducted primarily to determine whether some sort of alteration
takes place in microcrystalline rock types upon heating that
makes them easier to flake, especially to pressure flake.
If such a change does occur, the author proposed to determine
at what temperature alteration takes place and what are the
physical or chemical changes that cause alteration.
Whenever comparisons are made between heated samples
and unheated controls, the specimens were obtained from the
same core. An attempt was made to use material as free from
fossil inclusions or other heterogeneities as possible and
to obtain the samples from approximately the same area of
the core since textural differences do occur; for instance,
the area directly under the cortex is nearly always finer
grained than further within the mass. Throughout this sec
tion reference is made to
1. Critical temperatures: this should be interpreted
as 350C-400C for Florida cherts.
2. Slow rise in temperature: the materials being
heated were subjected to 50C elevations in
temperature until the testing temperature was
reached; they were left at each succeeding incre
ment for a sustained periodusually 24 hours.
3. Hapid rise in temperature: the materials being
heated were subjected to 500 elevations in
temperature until the testing temperature was
reached; they were left at each succeeding incre
ment for a short periodgenerally 1 hour.
22


3?
1. lo or. .' r occurred (c::c.p..* t. i o o<¡")
t. t-;n .:':::- s '
2. l'o n:.;. i-m occuto-np:'! ti'"'' ne n.oitoh.r_
v.ic raise-3 raro5.¡v to 'h. allotrnr. ir.
tvfc 3^0 C or ! :iu-.;v:-s ;,s.d xi- o ro- :.j 'e
y >!/._.locin oo.vu.rr on sil ocoo'riu'n. d-C'd-C when
the on to tu.1 v tetn te >'.r/>r'0 .;:¡ t ; r t olloviut:
tie ten.-u.u.r.e re be raise 1 o.V-. ly o.v si ?.. '
leavir.;; it 35tc,3 Ion* si utur u'.: r^rlod. lito'r.) lar
specie..'rih itoo. net explode te rs; til .
t-, IX ti." tarojcratura i;a: misad raeitl;.'. rrimicr.
or pt legato socio spol.lin.;, cv.cv.r-r.vl whenever tiro
i i ? --i el .ros relieved ito-ou tone oto.' ¡..t ItO'tj v< i. i lio ti
O. loving it to cool firoCv
3. Xf the. topenature v-cc rai&cO r-.aidto y, xpior-ion,
or i.t least sort.: t,p1 inocoi:-roi ot rali vstljy
hot not oi tea when tin. suteri.-O. v.os rureved free
tino oven c.S i'jCoC liitiiout sllmia. it to ecu. fir.,to.
to., iitplooion did net occur at 3Ct''0 ever. irles:. oto:;.
material. v.es removed free the Jtoh'.-C ovon i,u..-.Vd.ji,Ki>.,
7. IntereotispJ.u, ooi on l||reXj muo.l at ray
tempera cure -her. "u r i.vc.eiel :1 .:..-
etoly Jirou the c.von i.v -,'v- dnu'-ho.re ?::' .nih
raised slcv.lp- =vic, hi::-: 1 at the tostirr tor.; -
ture for- s sustain;! p .loi,
8. iftr.loslc.j res or c.'C'ru to '::-, tol e unto..-rial was
ti.ltcd r. -c...it tine, .tot the s.;;. tetiporatooio.
o, ¡.u:;¡ the tedian ature .s ruiae-j jar btoJ y 6 ornr;'-:! in p
noise td-tociaritetieh) ."n oltou honr at to., i on.to
aj.i.vys hs.nrd at SCC tile i,u.opr.e-5 ;.:io r n.ove.'
.:.. r ti'a n.u n ,;.: ..- un ni i owi n jt to.o "torsi; eon it.
lx vv.o :n :rd et vt'' 1 roc ?i h.-erd r
. .itoarj o': s war.'. ... .-t 'r,>' ;. ; n.
t-.h ..' -.i v.j:, teto vero ¡ l.eee Mrni'l.; t"to? p p-en h:n: nt
ov.;n r-.t 350C rm r-c. ,et;h. n cfcusv'-:-i ... "ton: 1/2 hour
but oto - .u x n eatopiio nto tchc 't n- n1 in-
hatoj a r.-nn-'tot t" r: heo './-::. on,it', nn 1 n-nto to
o.Jr toe. jin rauri .
11. '..lure to o -. to. to ¡.n.-, ; 1 :;"d dx/c i: ; 2 _ : u: r to. to
c\n"! Uc n ;-pic: ' o to .:n i.n r-i-
to-tolo. p to: to.i i: o :n.. nto n.n 'in. t. ototo in tonto-
nto.elp; cv Ac'hr. t:aih:u. -to to n t n: to to. to .. til
tho to .- ton. e to: tot' to too dev- ito't'tt. to.-. n; .. p to t-P
f/to !. to e < to to V : to-;- -. to i


ft
35
(salts, minerals, etc.) until a crackling sound is caused
or until this sound stops; to crackle when exposed to heat.
Explosion occurs when the stress that is causing decrepita
tion exceeds the elastic limits of the material.
When this study was initiated, several large chert
flakes were prepared in order to test their reaction when
heated. The author had intended to raise the temperature
slowly according to Crabtree's (personal communication)
instructions but the oven was progressing in degrees
centigrade while the author, unfortunately, was thinking
in degrees fahrenheit. The oven consequently heated more
rapidly than anticipated. At 40QC the rocks exploded.
The results are shown in Figure 4. Subsequent experiments,
conducted to determine the reasons for the rock failure.
resulted in one of the major contributions of this study.
Figure 4 illustrates quite clearly several facts
that refute objections which may be raised with regard to
the intentional heating and subsequent flaking of lithic
materials. The picture shows potlid fracturing and blocky,
angular flakes with no bulbs of percussion. This kind of
debris does not occur by intentional flaking. It differs
markedly from the thinning flakes found on archaeological
sites that are suspected of being thermally altered. It
resembles exactly what one would expect to result from too
rapid expansion and contraction as might occur in a forest
fire or if a rock had been placed in or near a hearth.
Subsequent testing of Florida cherts has revealed that:


Figure 5Results of Experiment Conducted to Test the Validity of "Flaking"
Hot Stones by Dripping Cold Water on Them: (a) The Rock Literally Fell Apart when
Flaking Was Attempted (note deviation from conchoidal fracture typical of flint
materials); (b) Magnified Area Illustrating the Crazing which Occurred.


Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
INVESTIGATIONS CONCERNING THE THERMAL ALTERATION
OF SILICA MINERALS: AN ARCHAEOLOGICAL APPROACH
By
Barbara Ann Purdy
March, 1971
Chairman: Charles H. Fairbanks
Major Department: Anthropology
A recent publication (Crabtree and Butler 1964)
suggests that prehistoric man may have found it advantage
ous to thermally alter lithic raw materials prior to manu
facture or final completion of chipped stone implements.
The specific objectives of this research and the
conclusions reached are as follows:
1 To establish whether a functionally desirable
change in chert occurs when it is subjected to heat. Ex
periments were conducted to determine the temperature and
length of time necessary to effect the detectable physical
alterations. Heated and unheated Florida cherts were studied
by petrographic analysis, x-ray diffraction, differential
thermal analysis, scanning electron microscope, atomic
spectrophometer analysis, standard rock mechanics test,
and the gas absorption surface area and porosity technique.
2. To determine whether primitive peoples might
have been aware of the advantages conferred by thermally
altering lithic materials. A review of the literature
revealed no completely adequate account describing this
technique. Enough records exist, however, to warrant the
viii


43
to either 350C or 400C as indicated, and then left at the
ultimate temperature for the designated period of time. The
oven was shut off and the samples allowed to cool in the
oven. The gradual onset of vitrification seems to go hand
in hand with an increasing ease in removing flakes. If
alterations take place too rapidly, dramatic, destructive
events occur. It should be emphasized that vitreousness
is not apparent unless the rock specimen is broken or
chipped after heating. The exterior surface of the heated
stone remains dull. This is illustrated in Figure 6b.
Discussion
The information presented to this point has been
mainly observation, and description. The data now remain to
be interpreted and the significance of the experiments dis
cussed.
It seems fairly clear that no reliable inferences
can be made from differences in weight loss and gain to
help in determining if archaeological specimens have been
thermally altered. Even under controlled conditions,
though significant differences were observed for the same
rock when flakes were either subjected to heat or kept as
controls, nothing reliable was recorded when making com
parisons between different rocks even when the method of
exposure was identical.
In addition, the amount of water driven off, whether
great or small, made no difference in the change which
ultimately resulted as long as the temperature effecting


C¡-;.
K> V'lll i i 1.1/ v ,
1900
AL--. :T >0
F] 51? t a;-d bh latin t t: on of 11 i ot ..
j. reriir,lo re Society, lo. 5, pa /L/Li.
' o t:;. Tne
London.
SCni'! nC.: ;> t AUL
lc7'7 le bilocas of Making Stone Ve aperas.
0 ^ .'. Ge c. 3.o "i.c ai1 d G ce-:n.e'r o f r:- ve
Cerril.or a> Vol. ora O^ V-O
Bulletin o::' tre
' The
S'iJ-
18??
le pos it o f Ar-r o i;- He a d s j e a r Fi s hi. i 11} N. X.
Annual Ae port of the Saltasenian Ihistitution,
for *t ho year 13V 6 7 a 207-d. 'Jas king ton.
Si. 1 'ii., CHILL 1 j.
133V A oe t-ch o i ilint Aidae Lie!:inr, C0anty, O 1 io.
Aiiriua 1 Ac oor b of trc Sinithson*.an Institi.tion ,
forthe year 185'-!-, pna Washington.
TULLIS, JA!7
1970 Aliar b a : 1 re ie r re Crien I 0J-i on i n Hoc 3 s Pr educed
by 3a 1 u fa in e 1 <: i nn in r. Science, V-.'l. 1 IS, a:. ILltnt,
I/s shingto.ru
WALIAOC, louNAo i' ALL 3, A.DAi. JCL dOBBsa
1952 The Coir.r.nchcs : Loren, of the Sort3 11sins.
University of Oklahoma i-ress, lomara
vhk::. 3. {*, n. 3a, all d, t. gijjgs
3 9 37 a A ' rj It -hr 1 c An al y s in 0 f H 01 3- r3 0 ci and inn 0 a 10 a
} 1 i n t So lonco, Ver.. 19 7 > op. 3. ;-37- 9 1/0 s h in j 10 n,
V'ILSOI.j a.CI3,3
3.1 >7 Arrov/noints, Orearle ads, Hnives of Are historic.
f inec Annul' 1 Alport of the oalthrcnfgs Insbitut- on ,
1.3 13 timal 1 usoua, par iTV:, *3113*5'*8 J
i? ash i apt o n.


?;1
Table A- .for the .resal of tii- xi'er*'- It was bo;,a3
ohafc this c-xperi! .ant. v< ou; ;h o U. -1 e > it provo to ';o a
.7 e 1 i ib 1 e end duexpe~¡aive nothod to br : :p 1 c;yoc: by a;;h o e o -
eg lata to act omine 11 chipped a true aoirs rad Ica.ti them-
all y altered. Th i a i .-ill b e d i a c u is o r 1 fur' V o a u \ O.y r t ho
he rin p: Arche col o.ji o o 1 upp' 5 c a t :1 on 5 1 :..l A a o a : ;h b a a re i ? a
I-airly consistent difference in reiyht hat or. an ha-.r;>
s ar pi e level, on an i n r e r a or, d e 1 e v a I t he re is o v o r lor .
lb e refere even if an in ve s b i j a t o r i:t: c . < a f, ;c u a f d e1 ah oi t
the roc> 1 e arae rec or e r ing (t h a t is, e on vc- e, e orip c s 5T-:L on,
e t c -. ) ho v/oul d ha ve t o be ca r e fu 1 i n a s s :l gn x'>y t o o j arc h
iuip optarce to v; c :i gat 1 o s s. Thi s c :'p e i i.: :: n t t: 1 s;: r a i o;; t e a
vhet ¡die v: eight loss at 100 C is probe hi. y not toe indicative
since it ueulci fluctuate greatly dependire on hov; bmp cor-
it, ions v;o:cvr prior to heating. It has V-on deans trate 1
tii at an j spree i able chtmne 1-1 n eight corn's if the -a a. pi as
am- left at room temperature after being removed iir:n a
oi t -a v i r'.i a :. t (see Tab} e 3 ) i
1 ,11e; a 1 a : ro: . tbe field wn xch oere thoup;ht to h avt-
c /:; t1 o xvi & 1 i % al tena cl s i r; c a ia e p ;& re qv< i t e 1 -; s t ro us an d
i w r. : . i u : i o d a p :V V i .* h : *1 eJ: vc r v a d in o:: de r t o c; ei..
pore weight losses vifS. ob:u. epeoirieus t'-at vore Intown no!:
to h."'.'a bee- ar*sv 1 ea' ? y !>?t"d The r-¡ ro 1.us nr; :i \ i.n i?
Vohi, 3,. It;hr tarvlis or n >*ad ;;i ch 'T bX<: A, i t d 3
.. i v o r. t t' ¡ a t i,!: e r c i: i a s i. p : i 1; cr. b d i f f ore nc e i r the
e vi i of i o i s o r re p; i v. o o f e 1 : . e n th^ r a t c r :I a 1 s that :'.
\- a ( "i i rj s j. c bc o f b o iv p v 1 c\ 1 ;p >e t r d c ntv . *. a h 1 ^ :
Uh;; bed f e. b.j fi.e.l ti.... Are rose] to ex'* li.U.
ti ....


ARCHAEOLOGICAL APPLICATION
If an archaeologist suspects that the chipped stone
remains he recovers from a site have been thermally altered,
it would be desirable to subject these materials to a
standardized test in order to eliminate the "guess" factor.
This is important since thermal alteration presente informa
tion concerning not only stone technology, but contributes
ultimately to a greater understanding of prehistoric man's
behavioral patterns. This becomes even more valuable if an
investigator is working on time levels where only stone
artifacts have been preserved.
The following discussion involves a review of the
many experiments conducted throughout the course of this
study to determine if one or more of these might feasibly be
applied to site materials. For a fuller account of these
experiments, the reader is advised to refer to the section
on Methodology.
Weight loss cannot be used as a criterion to
determine if specimens had been thermally altered because
experiments demonstrated that heated specimens tended to
take on moisture again. In other words, if an archaeol
ogist weighed, heated, and reweighed outcrop materials along
with site materials to check differences in weight loss he
probably would find no significant difference. And even if
82


31CGIVlPr IC V¡ aKaTCH
Bar Do xa Am? Kurdy v/aa bo:?ii August 2::, IS-2' at San
Diego, California. Ir. June, 1945, she v/as graduated fro.:.
He rb e rt Ho cv r Mi ah 3c I* o o 1 In 0 une 194C s h e re c e 1v e d
the decree of Bachelor of Arts -..iih s major in Zoology from
3an Diego State College. In 1949, she viai employed at
Scripps Institution of Oceanography at La Jolla, CalifOx-r.Ui
in the Departnent of Karine Microbiology. iron 19-,9 to
1993, she vas employed in various depuxty, onto on the corpus
of the University of California at Davis, Iron i960 to
i960 :-nd intermittently to 1967, she typed theses and o- ?vsd
a 3 Ihocis id it or at Kashington State University, Pullrou,
Washington. In the fall of 1964, she enrolled in the
Department of Anthropology at bashin.:..tors State University.
Freo- 1965 to 196?, she was a lie search As si etant and receive!
the Kao ter of Arts degree in 1967* In 196?, she- enrolled in
the Department of An thro pol cry at the '.river city of Florida
in order to versus vorh leading to the degree of Doctor cl'
Philosophy. In July, 19'69- she attended a four-v.reh flint--
working session at Shoshone Halls, Idaho sponsored by Idaho
State University with funds granted by r.ho National Scicr-cc
Pound a ti on, She v/as a teaching assistant from 1666 to i y?C
in t he Do; 3 rt j nst? tatioe \r> the Univorgi ty 0o 1 j.v",e at the It;i < rsi -y
96


88
by those anth ors m ay have revealed th i- t 1 .
rot subjected to an open fire, that they j-.ey have b-on
1 )uricd or that 11 *>oy .may havc becu allo wc-c to rorain in
the ho :t:1 np; envir-onvenf for an extended p eod of time.
I':y in v Motivations Lave sbov;r. that;
i e M at e r i -a 1 s r e si o v e d f ron a ho t c v on d id n o t :v. c -
ture when exposed immediately to a cool env ir cone nt if the
toiispcrafnecessary to effect an alteracin in the rock
bed been reached si owly and 'maintained for a lory enough
period for the proee?.? to be comp3 eted,
P- Under point tensile load, g greater reduction
in strong rh occurs vkon- the rock material a removed,
i:,mediately iron ?. hot over: to a cool environment l initei
tec> tr; pave resvIts as foliov;a : meterials heated to 3fC 0
but allowed to cool in the oven had a 40# less in strength
ov c r t h e 'an he e. t o d c on tro 1, As amp 1 e f r o ? u the s ane n odul e
which hod been heated to 350 C sard exposed immediately to
a cool environment inri a Gyp loss in strength--an additional
redaction of 83,1. It is possible than for certain extremely
ire j an t i c rock typ e a e y r> o snro t c the s e incr eased stresses
v?ad cir i.l. 1 j t c ¡:¡ ;.!:? c Li p\on:- e as ic i
i'hc accounts of the rd^occ -mentioned reporters are
p rob o h 1 y a o o i r o t r c.c; f r r a s t h o y p o Th e i r de s c r:i p t i on s ,
p c-, in-Vr; be..a irnntenyr^fa t-orc boo case they ere
in a o :p 1 i; .ro f ho r than in c err c c t,
Anf t; vr ojc c-!:ior uhieh :: ipht Ve raisad v:ith regere
to pr.i iba' n 5 r ha: hr.; of .. -oaks von 1 a be if-'h ice ho
no h. o v-L "v h. .. no : y of hn*-..' to.. hirn I .La*


PLEASE NOTE:
Some Pages have indistinct
print. Filmed as received.
UNIVERSITY MICROFILMS


49
. . principles of surface chemistry .... When a
crystal consists of highly polarizable anions of large
size, together with small, highly charged cations,
then the anions will be pushed to the surface of the
crystal and the cations will be recessed. Thus in a
microerystal of quartz oxygen ions predominate at the
surface, while the silicon ions are depressed. It is
believed that each microcrystal of quartz then has a
negatively charged "skin," and effectively repels
adjacent randomly oriented microcrystals . fracture
probably takes place between the polyhedral blocks
because of the surface repulsion forces (Folk and
Weaver 1952: 507-8).
When the rocks are subjected to critical temperatures, there
may be a change in the position of oxygen and silicon ions
as described above. If the ions become too excited when
temperature is applied rapidly, explosion may take place.
This may also explain the clicking sounds which occur and
often result in exfoliation when the material is rapidly
cooled. Perhaps the reason these clicking sounds aren't
heard when the material is removed after a sustained period
is because the process is completed and no further change is
taking place.
Failure was accompanied by peculiar "clicks." These
"clicks" were heard early in the cooling period and
never during the heating period, when the rate of
temperature change was lower. When the cups were
heated to a slightly higher temperature, no higher
percentage of failures was observed (Pressler and
Shearer 1926: 307).
Material that has been heated to 500C is no easier to flake
than that left at 350C for prolonged periods (see Fig. 6b).
A number of samples were heated to 600C; subsequent chipping
of these specimens did not reveal any further change either.
However, point tensile strength tests, to be discussed later,
do not support this observation since there is increased
strength loss with increased temperatures under point tensile


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V ill 1 : ; l 1 .


90
closer together when certain materials other than SO2 serve
as fluxes When the flaw is introduced which is preliminary
to and necessary for fracture to occur, the heated rock
responds more like glass than a rock aggregate. In other
words, crystal boundaries are no longer interfering with
the removal of flakes. These statements have been sub
stantiated throughout this dissertation by rock mechanics
tests, scanning electron microscope illustrations, analyses
demonstrating a reduction in surface area of heated mate
rials, as well as intuitive observations and experiments.
2. Prehistoric peoples were aware of the advantages
conferred by thermally altering their lithic materials be
cause the chipping debris recovered from archaeological
sites has been intentionally flaked following subjection to
heat. This is apparent because the flakes have bulbs of
percussion which demonstrate that there has been a point
of impact. Bulbs of percussion are not exhibited if rocks
eaqplode when too rapid heating or cooling occurs. Instead,
there are "potlid" fractures or conchoidal fractures which
do not show a point of impact. The flaked surface of the
altered specimens are extremely vitreous, varying appreci
ably from outcrop samples of the same materials. Very often
also, due to the presence of minute amounts of iron, there
is a color change from grey-beige-brown to pink-red. While
color change occurs at a lower temperature than the signifi
cant change resulting in easier flaking and will not occur
at all unless iron is present, it may be considered a reli
able factor if used in conjunction with vitreousness.