Rocks and minerals of Florida

STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY

FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director

SPECIAL PUBLICATION NO. 8

ROCKS AND MINERALS OF FLORIDA

A GUIDE TO IDENTIFICATION, OCCURRENCE,

PRODUCTION AND USE

By
Ernest W. Bishop and Lawrence L. Dee, Jr.

Illustrated by Andrew R. Janson

Tallahassee, Florida
1961

LETTER OF TRANSMITTAL

September 18, 1961

Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida

Dear Governor Bryant:

The Florida Geological Survey is publishing Special
Publication No. 8, a general discussion of the basic identi-
fication of minerals and rocks. We have had a great demand
for such a publication from all of the schools in the State,
school children, and laymen who find geology of interest.
The publication of this pamphlet will be accompanied by a
collection of typical Florida minerals and rocks and will
meet an expressed need of the citizens of Florida.

We are pleased to provide this service, and hope that
the pamphlet canbe utilized in some of the school instructional
programs.

Sincerely yours,

Robert O. Vernon, Director

PREFACE

This booklet is written to accompany a collection of
18 rocks and minerals found in the State of Florida, and to
serve as a guide tothe identification, occurrence, production
and use of Florida's most common rocks and minerals.

It is primarily intended to be a simplified general
reference for the student; therefore, technical information
and detailed descriptive material is minimized. For students
who would like to further pursue the study of rocks and
minerals, a list of references is added at the end of this
pamphlet. Most of the books listed are available inthe public
libraries.

Of the rocks and minerals described herein, some are
relatively unimportant economically, though of common
occurrence throughout the State. Others have considerable
economic importance, but do not occur in sufficient quantity
to be of commercial value. Production data for those rocks
and minerals commercially exploited are based on reports
compiled by the U. S. Bureau of Mines, in cooperation with
the Florida Geological Survey.

This booklet is also intended to give the reader an
overall perspective of the importance of each mineral and
rock in the mineral economy of Florida.

TABLE OF CONTENTS

Page
Introduction..... ............................... 1
Minerals..................................... 1
Physical properties .... .................. 2
R ocks ...................................... 4
Igneous .................................. 4
Metam orphic ............................. 4
Sedim entary.............................. 4
Specimens in the sample set..................... 5
Limestone (Specimen No. 1) .................. 5
Key Largo limestone ......... ............ 6
Miam i oolite................................ 7
Coquina.................................. 8
Ocala limestone..... ..................... . 9
Suwannee limestone .............. ......... 9
Tampa limestone.......................... .10
Calcite ................................. 11
Dolomite (Specimen No. 2)..................... 12
Common clay (Specimen No. 3). ............... 13
Kaolin (china clay) (Specimen No. 4)........... 15
Fullers earth (Specimen No. 5). ............... 16
Quartz sand (Specimen No. 6)................. 17
Sandstone (Specimen No. 7)................... 18
Chert (Specimen No. 8)....................... 19
Limonite (Specimen No. 9) .................... 20
Ilmenite (Specimen No. 10) ................... 22
Rutile (Specimen No. 11) ..................... 23
Zircon (Specimen No. 12) ..................... 24
Staurolite (Specimen No. 13).................. 26
Gypsum..................................... 27
Anhydrite (Specimen No. 14) .................. 28
Phosphate rock (Specimen No. 15) ............. 29
Peat (Specimen No. 16) ....................... 30
Fossils (Specimen No. 17).................... 32
Sea shells (Specimen No. 18). ................. 34
Other rocks and minerals of Florida. ............. 35
Agate and chalcedony......................... 35
Aragonite ................................... 35
Diatomaceous earth.......................... 36

Page

Pyrite............ .............
Vivianite ......................
Mica ...................*......
Petrified wood .................
References.......................

ILLUSTRATIONS

Figure

Key Largo limestone ..................
Miami oolite .........................
Coquina...............................
Ocala limestone ......................
Calcite ..............................
Dolomite. ............................
Clay..................................
Kaolin (china clay) ....................
Fullers earth .........................
Quartz sand ..........................
Sandstone. ...........................
Chert.................................
Lim onite .............................
Ilm enite .............................
Rutile ...............................
Zircon................................
Staurolite ............................
Gypsum and anhydrite .................
Phosphate rock .......................
Peat .................................
Fossils...............................
Prehistoric life........................
Sea shells.............................
Dragline, land pebble phosphate mining .
Limestone quarry .....................
Dredge, heavy minerals ...............

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10
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12
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14
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18
19
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21
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S23
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26

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ROCKS AND MINERALS OF FLORIDA

A GUIDE TO IDENTIFICATION, OCCURRENCE,

PRODUCTION AND USE

By
Ernest W. Bishop and Lawrence L. Dee, Jr.

INTRODUCTION

In order to familiarize the reader with some basic
definitions and terminology, the following introductory
section is included.

Minerals

A mineral is a naturally occurring inorganic substance
having a characteristic chemical composition and definite
physical properties. Most minerals have a definite geo-
metrical arrangement of component atoms which, under
favorable conditions of growth, produce smooth planes called
crystal faces. Such geometric forms are called crystals.

Most minerals are compounds, formed as chemical
combinations of two or more chemical elements. Some
elements, however, such as sulfer, gold and silver, may
occur pure or uncombined with other elements; these are
known as native elements and are also minerals.

Ernest W. Bishop, Geologist, formerly employed with the Florida Geo-
logical Survey. Lawrence L. Dee, Jr., graduate student, Florida State University,

FLORIDA GEOLOGICAL SURVEY

Physical Properties

The physical properties of minerals may vary some-
what, but are generally constant to a degree that makes them
useful aids in identification. For
most common minerals, identifi-
cation on the basis of physical A CO
properties alone is sufficient.

Color: The color of a mineral is
one of the first physical prop-
erties to be observed. Some
minerals have a fairly con-
stant color, while in other
minerals the colors vary
greatly because of the pres-
ence of impurities.

Streak: Streak, which is the color of the powdered mineral,
is more constant than surficial color and therefore
more important in mineral determinations. It is
usually obtained by rubbing the mineral across apiece
of unglazed white porcelain, although very hard
minerals may be pulverized with a hammer and the
color of the powder examined on a piece of white paper.

Hardness: The resistance of a mineral to scratching or
abrasion is termed hardness. To express hardness
an arbitrary reference scale (Mohs scale) is used.
The standard scale, which consists of 10 common
minerals arranged in order of increasing hardness,
is as follows:

1. Talc 6. Feldspar
2. Gypsum 7. Quartz
3. Calcite 8. Topaz
4. Fluorite 9. Corundum
5. Apatite 10. Diamond

By using the above reference minerals, the hardness
of an unknown mineral can be determined. For example,

SPECIAL PUBLICATION NO. 8

if the unknown mineral will scratch feldspar but not
quartz, the hardness of that mineral is between six and
seven. In other words, a mineral will scratch any
other mineral equal to it in hardness, or any mineral
that is softer. Most reference books on mineralogy
list the hardness of minerals according to the Mohs
scale. The determination of the approximate hard-
ness of minerals less than six or seven is greatly
simplified by using the following common items:
Fingernail up to 2. 5
Copper coin up to 3. 0
Knife blade up to 5. 5
Window glass 5.5
Steel file 6. 0 to 7. 0
Specific gravity: The specific gravity of a mineral is its
weight compared to an equal volume of water. For
example, the mineral rutile has a specific gravity of
about 4. 2 which means that rutile is 4.2 times as
heavy as water. Rutile is considered a heavy mineral,
whereas quartz (S. G. 2. 65) is not considered a heavy
mineral.
As a general rule, this property of an unknown
mineral can be estimated as being heavy or light by
comparing its weight with that of an equal sized piece
of a common mineral of known specific gravity.
Cleavage: The tendency of a mineral to break or split along
smooth flat planes is known as cleavage. Some min-
erals show perfect cleavage in several directions,
whereas other minerals have no cleavage at all. For
example, calcite breaks into rhombohedrons which re-
semble distorted cubes, but quartz has no cleavage and

FLORIDA GEOLOGICAL SURVEY

breaks into irregular fragments like ice. Because
cleavage is always constant for a given mineral, it is
usually used as an aid in mineral determination.

Rocks

Rocks are naturally occurring mineral masses that
form the solidpart of the earth. Rocks are composed of one
or more minerals and may be hard as in marble, basalt and
granite; or soft or unconsolidated, as in clay, sand or gravel.
There are three main types of rocks, each of which was
formed in a different way. These types are called igneous,
metamorphic and sedimentary.

Igneous Rocks
Igneous rocks are those which have cooled and solidified
from an originally hot moltenliquid. When the moltenliquid
comes to the earth's surface from volcanoes, it is known as
lava. When it cools and hardens more slowly below the
earth's surface, it produces rocks such as granite. Igneous
rocks occur only at great depths below the ground surface
in Florida.

Metamorphic Rocks

Metamorphic rocks are igneous or sedimentary rocks
which have undergone considerable change because of heat,
pressure, or both. Some common examples are marble and
slate. Metamorphic rocks do not occur at the surface in
Florida, but have been encountered at great depths in oil
test wells.

Sedimentary Rocks

Sedimentary rocks are those formed by the deposition
of sediments derived from the destruction of other rocks,
and by chemical and biological precipitation. In Florida, they
include all those rocks exposed at the surface. There are
three essential phases inthe formation of sedimentary rocks:

(1) The sediments must essentially be derived by the
breaking down or weathering of older rocks. This is accom-
plished by mechanical, chemical and biochemical processes.
Mechanical erosion consists of the fragmentation of rocks
by the action of water, wind, frost, ice, plant roots and falling

SPECIAL PUBLICATION NO. 8 5

or sliding caused by the pull of gravity. In the chemical
process, soluble rocks are dissolved byacidic ground water
or surface water. Plants and animals through their bio-
chemical processes also cause
some decomposition of rock mate-
rial.

(2) The material produced
bythe breaking down of rocks must
be transported to the area in which
they are to be deposited. The trans-
porting agent is usually running
water such as streams or ocean
currents, but some material is
moved by the wind, ice and the
direct force of gravity.

(3) Deposition takes place when the velocity of the
transporting agent is reduced, as when a stream enters a
lake or ocean. Material is also deposited by chemical and
biological precipitation. The sediments generally become
consolidated into hard rock as a result of compaction,
cementation, or both. Compaction is caused by the weight
of overlying sediments which tend to squeeze out much of the
water, while cementation takes place as the mineral matter
in the contained water is precipitated out. This precipitation
results inthe formation of minerals which bind the sedimen-
tary particles together to form consolidated rock.

SPECIMENS IN THE SAMPLE SET

Limestone
(Specimen No. 1)

Identification: Limestone is a sedimentary rock composed
principally of the mineral calcite, CaCO3. The calcite
inlimestone ranges from fragments large enough to be
seen with the naked eye to small chalky particles too
small to be seen even under the microscope. Florida
limestones range from hard, compact, crystalline
rocks to soft, chalky masses, generally white, light

FLORIDA GEOLOGICAL SURVEY

gray or light grayish brown
in color, and commonly con-
tain fossil shells and shell SS
fragments. Limestone may SPECIMEN
be easily identified by the I
application of a drop of cold
dilute hydrochloric acid which
causes the calcite particles i
to effervesce freely.

Occurrence: Limestone underlies
all of Florida, but in many
parts of the State it is covered by the sand and clay
that forms the land surface. Limestone in the State is
divided into the following types:

Key Largo Limestone

The Key Largo limestone is a fairly hard, white to
light gray rock, which contains numerous fossil corals.

Figure 1. Key Largo lim@-ton@,

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Some of the s e corals have been partially dissolved by ground
vater and the spaces remaining filled with crystalline calcite.
Che Key Largo limestone is found at the land surface in the
Florida Keys from Sand Key to Loggerhead Key.

Miami Oolite

Oolites (oolites) are small rounded grains so named
becausee they look like fish eggs. Oolites are formed by the
deposition of layers of calcite around tiny particles, such as
;and grain or shell fragment. The Miami oolite is a fairly
;oft, white limestone made up principally of oolites with
;ome quartz sand present.

It is foundat land surface inparts of Broward, Collier,
)ade and Monroe counties.

Figure 2. Miami oolite.

FLORIDA GEOLOGICAL SURVEY

Coquina

A coquina limestone is one composed of whole or
broken shells and quartz sand grains that have been more or
less firmly cemented together. In the coquina found in
Florida the cementing agent is principally calcite.

It is interesting to note that coquina has for over 400
years been used as a building stone inFlorida and is prized
today for its beauty as incorporated in modern architecture.

Coquina is found at land surface along the east coast
of Florida from St. Johns to Palm Beach counties, but is
rarely found more than 3 miles inland from the coast.

::--_ L ._?- .-..'.'.,. . .. .... ?.. :" '

Casidllo de.
c(an.Marco:

Figure 3. Coquina.

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------.

-I F

5~5~-~Ti

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Ocala Limestone2

The Ocala limestone is a most remarkable limestone
deposit inthat it is composed of almost pure calcium carbon-
ate (CaCO3), shells of small sea creatures and very tiny
chalky particles. Generally the Ocala limestone is soft and
porous, butinplaces it is hard and dense because of cemen-
tation of the particles by crystalline calcite.

Figure 4. Ocala limestone.

The Ocala limestone underlies almost all of Florida,
but is found at the surface of the land only in parts of the
following counties: Alachua, Citrus, Dixie, Gilchrist,
Holmes, Jackson, Lafayette, Lake, Levy, Madison, Marion,
Polk, Sumter and Taylor.

Suwannee Limestone

The Suwannee limestone contains a very high percent-
age of calcium carbonate and, though it is not as pure as

2The Ocala limestone as used here includes the Ocala group of limestones
consisting of the Crystal River, Williston and Inglis formations.

FLORIDA GEOLOGICAL SURVEY

the Ocala, in Panhandle Florida it approaches the Ocala in
purity. The impurities in the Suwannee, principally quartz
sand and clay, may amount to 10 percent or more of the
rock. In general, the Suwannee is somewhat harder and
more compact than the Ocala limestone.

The Suwannee limestone is found at land surface in
parts of Citrus, Hamilton, Hernando, Holmes, Jackson,
Jefferson, Lafayette, Lake, Madison, Pasco, Sumter, Tay-
lor, Walton, and Washington counties.

Tampa Limestone

The Tampa limestone is much more variable in its
compositionthan either the Ocala or Suwannee. The impuri-
ties, which may be quartz sand, clay and phosphate, range
from about 20 to as high as 70 percent of the rock.

In general, the Tampa limestone is a hard, massive,
crystalline rock, andin some parts of the State is character-
izedbythe presence of small cavities causedby shell material
being dissolved out of the rock.

The Tampa limestone is exposed at land surface inthe
Tampa Bay area in Hillsborough and Pinellas counties and in
adjoining Pasco County. In west Florida, this limestone.may
be found at land surface in places along the Apalachicola
River inJackson, Gadsden, and Liberty counties. Numerous
surface exposures are also found in Wakulla and Washington
counties. The Tampa limestone is near the surface in several
other counties in the western and northern part of the State,
but generally is exposed only in sinkholes.

Production and use: Florida produces over 28,200,000 tons
of limestone, lime and dolomite per year valued at
nearly $38 million. This amounts to more than 58 per-
cent of the total mineral production.

Most of the limestone produced in the State is
crushed for use in making hard surface roads and as
an aggregate in concrete. Limestone is also used in
agriculture as a soil conditioner. Portland cement,
railroad ballast, riprap, building stones, lime, chemi-
cal industries and other miscellaneous uses account
for the remainder of Florida's production.

SPECIAL PUBLICATION NO. 8 11

Calcite

notification : The mineral calcite, which makes up lime-
stone is composed of calcium carbonate (CaCO3). It
varies in color from white or colorless to shades of
yellow, orange, or gray. Calcite has a hardness of
3.0, a specific gravity of 2.7, and a white or colorless
streak. It breaks up readily into crystalline forms
called rhombohedrons and canbe identified further by
its effervescence in cold dilute hydrochloric acid.

currency: Calcite, though of common occurrence in
Florida, is a very interesting mineral, found in a
variety of forms. Inlimestone quarries calcite canbe
found occurring massively or as long needle-like and
block-shaped crystals within open cavities or seams in
the limestone. In natural solution caves, such as the

.

I, .

_.I -
.;... %
@,., ". .,
I : ~'

:~'lt:%.[g, :-. ;,

.ji W '' :; L,. .

Figure 5. Calcite.

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Marianna Caverns, calcite is often found forming
stalactites or stalagmites, and more rarely "cave
flowers. As the principal mineral in sea shells cal-
cite is found in both Recent and fossil marine and fresh
water animal remains.

Dolomite
(Specimen No. 2)

Identification: Dolomite is a sedimentary rock composed
principally of the mineral dolomite, CaMg(CO3) The
mineral dolomite has a white, light brown or pink
color, a white streak, and a hardness of 3. 5. The
crystals, if discernible, are usually small and the
crystal surfaces are somewhat curved. The test for
dolomite is the same as that for calcite, except that
dolomite effervesces very slowly in cold dilute hydro-
chloric acid, and more vigorously in warm acid.

Figure 6. Dolomite.

SPECIAL PUBLICATION NO. 8

Occurrence: Dolomite is usually found closely associated
with limestone deposits occurring in Florida in parts
of Polk, Sarasota, Manatee, Citrus, Levy, Dixie,
Taylor, Jefferson, Wakulla, Gadsden and Jackson
counties.

Production and use: Dolomite can be used for most of the
same purposes as limestone except for making Portland
cement, because in this process the magnesium (Mg)
interfers with the setting properties of the cement.
In Florida, most of the dolomite produced is used as
agricultural lime, though some is mined and used as
cut stone.

The amount and value of dolomite mined in the
State is less than that of limestone, although the two
are combined and the production of the two materials
amounts to over 28,200,000 tons valued at over $38
million per year.

Common Clay
(Specimen No. 3)

Identification: Common clay is a sticky, plastic type of sedi-
mentary rock that is composed primarily of varying
amounts of clay minerals, quartz sand, calcite, iron
oxides, organic impurities and other materials. Most
of the clay in Florida was originally deposited as a mud
in seas, lakes, rivers, or on deltas. Clay may occur
in a wide variety of colors depending upon its miner-
alogical composition, impurities, and the amount of
weathering which it has undergone.

Occurrence: Common clay occurs in almost every county
north of the latitude of Lake Okeechobee, though in a
number of counties it is of too low a grade to be used
for anything except for building roads. Escambia and
northern Santa Rosa counties have vast reserves of
very high grade clay. Large deposits of good common
clay exist in the St. Johns River valley from Jackson-
ville to Lake George, with smaller deposits of good

FLORIDA GEOLOGICAL SURVEY

Figure 7. Clay.

clay occurring in many of the counties in the northern
and western part of the State.

Production and use: The principal use of common clay in
Florida is as an additionto sandin the construction of
roads. Florida clays are also usedinthe manufacture
of Portland cement and lightweight aggregate. Other
products made from common clay include bricks, sewer
pipe, and roofing. The almost complete lack of pro-
duction in Florida of the last three named products is
due to complex economic factors.

Production figures are not available onthe amount
of common clay used in the State.

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Kaolin (China Clay)
(Specimen No. 4)

Identification: Kaolin is a soft, lightweight, often chalk-like
sedimentary rock that has an earthy odor, and in Florida
is generally light in color and associated with large
amounts of quartz sand. Kaolin is composed chiefly of
the clay mineral kaolinite, the crystals of which are so
small that they can be seen only under the electron
microscope. Kaolin is generally quite porous and will
stick tothetongue; it also has the distinctive property
of slaking or disintegrating rapidly when placed in
water.
Occurrence: Florida has a very large known reserve of
kaolin, the largest deposits occurring inthe east cen-
tral part of the State from southern Clay County to
northern Highlands County. A smaller deposit occurs
in west Florida in a narrow belt extending from Jackson
County into Santa Rosa County.

Production: Florida's active kaolin mines are located in
Putnam County. These mines produce over 17,000

Figure 8. Kaolin (china clay).

16 FLORIDA GEOLOGICAL SURVEY

tons of kaolin yearly, which accounts for less than one
percent of the total mineral production of the State.

Use: Kaolin is used in making porcelain, paper, oilcloth,
linoleum, paint, soaps, tooth powder, crayons, tex-
tiles, and other products. Kaolin produced in Florida
is usedalmost exclusively in the ceramics industry in
the manufacturing of china and standard porcelain.

Fullers Earth
(Specimen No. 5)

Identification: Fullers earth is the name applied to certain
clays that have the ability to adsorb coloring matter
from vegetable, mineral and animal oils. Some of the

c-5ticks fo the
.F tongue

Figure 9. Fullers earth.

. i,
~

*^B^ iAilO

SPECIAL PUBLICATION NO. 8

fullers earth clays are not readily distinguishable from
common clay, but in general the fullers earthfound in
Florida is light green or gray in color, has a greasy
feel when wet, and has a low specific gravity. Fullers
earthwillnot slake or disintegrate readilywhenplaced
in water, as will kaolin.

Occurrence: Sizable deposits of fullers earth are known
to occur near the surface of the ground in Gadsden,
Marion, Pinellas and Manatee counties. Small deposits
are known in many other counties, and are often en-
countered in the drilling of wells.

Production: Florida's activefullers earth mines arelocated
in Gadsden County, but in the past the material has been
mined in Marion and Manatee counties. The Gadsden
County mines produce over 245,000 short tons of fullers
earth per year, valued at more than $6 million.

Use: Fullers earth, because of its high adsorbing powers, is
usedas a cleansing agentin service stations, machine
shops, factories and other places where oil and grease
are spilled onfloors, machinery, etc. Fullers earth is
used quite extensively as a carrier for insecticides and
fungicides, as a filtering agent for removing color from
mineral and vegetable oils, and as a mineral filler in
soaps, some plastics, paints, and polishes.

Quartz Sand
(Specimen No. 6)

Identification: Quartz sand is a loose, unconsolidated material
of small grain size composedprimarily of the mineral
quartz. Quartz is crystalline silica, SiCO, and may be
of any color though generally in Florida quartz sand is
colorless or white. Regardless of color,however, the
streak is always white. The specific gravity of quartz
is 2. 65 and the hardness is 7. 0.

Occurrence: Though common quartz sand is the most abun-
dant surface material in the State, the deposits are

FLORIDA GEOLOGICAL SURVEY

Figure 10. Quartz sand.

not extensively developed. Sand is mined on a limited
scale in almost every county in the State, with the
principal sand producing counties being Polk, Dade,
and Putnam.

Production and use: Florida produces over 6.6 million tons
of sand annually, valued at about $5 million, with the
principal user being the building industry. This ac-
counts for more than 12 percent of the State's total
mineral production.

Florida quartz sand is also used for making glass
and for grinding andpolishing metals. Other uses are
as molding sand, blast sand, filter sand, and fill sand.

Sandstone
(Specimen No. 7)

Identification: Sandstone is a sedimentary rock commonly
composed of quartz sand grains cemented together by
silica, calcite, iron oxide, or other mineral substance.
Depending upon the amount and character of the cemen-
ting agent, sandstones may be almost any color. In

SPECIAL PUBLICATION NO. 8

Florida, the colors generally range from almost pure
white through shades of yellow, orange, red and brown.

Occurrence: The occurrence of sandstone is limited in
Florida largely to the red sandy clay formations of
the central peninsula and northwestern part of the
State. It generally occurs as thin discontinuous layers
or small nodules, though it has been observed in beds
up to 10 feet thick.

Productionanduse: No commercialuse is made of the sand-
stone found in Florida, though it has been used on a
very limited scale as a building stone.

Figure 11. Sandstone.

Chert
(Specimen No. 8)

Identification: Chert, also known in Florida as flint or flint
rock, is an extremely fine-grained variety of the
mineral quartz. It is characterized by its extreme
hardness (7.0), shell-like fracture, and the sharpness
of the edges of broken fragments. Florida's cherts
are generally gray in color, though some are bright
shades of blue, red, yellow and orange.

Occurrence: Chert is found in Florida in association with
some of the limestone formations, especially the Ocala.

FLORIDA GEOLOGICAL SURVEY

Figure 12. Chert.

The material was formed by the replacement of calcium
carbonate with silica carried in circulating ground
water, as shownbythefact that much of the chert still
contains traces of the fossils that were present in the
original limestone. Chert is found at the surface of the
ground in many of the northern andwestern counties of
the State, especially Wakulla, Marion, and Citrus
counties.

Production and use: Chert was utilized by Florida's Indians
in the manufacturing of axe heads, spear heads and
arrow points. The hardness and variety of colors
make chert suitable as a semi-precious stone.

Limonite
(Specimen No. 9)

Identification: Limonite, a compound of iron, oxygen and
hydrogen (2 Fe2O3 3 H20), is a yellowish brown to
dark brown or black mineral. Limonite has a yellowish

r- ,~-

SPECIAL PUBLICATION NO. 8

brown streak, but its hardness depends upon the form
in which it occurs. Yellow ocher, which is a mixture
of limonite and clay, is so soft that it easily leaves a
yellowish brown mark onpaper or cloth, while the dark
brown or black variety of limonite can range upto 6.0
in hardness. The specific gravity of limonite ranges
from about 3.4 to 4.0. Small amounts of limonite give
a yellow or buff color to clays, limestone and soils,
andas a scum on swampwater it is often mistaken for
oil because of its iridescent color in reflected light.

Occurrence: Impure limonite occurs in many counties in the
State, often appearing as a rust-like material staining
sand and binding it together. A deposit of fairly high
grade limonite is known to exist near Chiefland in Levy
County.

Production and use: It is reported that the Confederacy mined
limonite from the deposit near Chiefland for the manu-
facturing of cannons and cannon balls. A deposit of

Figure 13. Limonite.

FLORIDA GEOLOGICAL SURVEY

yellow ocher in Flagler County has been worked for
pigment, but no production has been reported since
1953.

Limonite is used commercially as an ore for iron
and as a pigment in paints.

Ilmenite
(Specimen No. 10)

Identification: Ilmenite is an iron, titanium oxide, FeTiO3.
It is black to brownish black in color with a black to
brownish red streak. The specific gravity varies from
4.3 to 5.5 and the hardness from 5.0 to 6.0. Ilmenite
is naturally slightly magnetic, but the magnetism can
be greatly increased by heating. In Florida, ilmenite
occurs as rounded sand-size particles.

Occurrence: A small percentage of minerals with specific
gravities higher thanthat of quartz arefound scattered
in most of the unconsolidated sands of Florida, es-
pecially coastal beach sands. These minerals which
include ilmenite, rutile, zircon, staurolite and others,
because they are heavier than quartz, are known as
"heavy minerals. Wave or wind action may concen-
trate these minerals by carrying away the lighter quartz

Figure 14. Ilmenite.

SPECIAL PUBLICATION NO. 8

grains. Such concentrations are common along present
beaches of the State and also along beaches that were
formed when the sea stood higher than it does now.
Deposits of heavy minerals maybe recognized by their
black color due to the presence of ilmenite, which is
generally the most abundant mineral in such deposits.

Production: Ilmenite is produced from heavy mineral sands
in Clay, Duval, and Indian River counties. The pro-
duction of ilmenite along with rutile, which is also a
titanium mineral, is valued at more than $6. 5 million
annually.

Use: The chief use for the mineral ilmenite is in the manu-
facturing of titanium dioxide pigment for white paints.
Ilmenite, along with rutile is used for coating electric
welding rods and also as a source of titanium metal.

Rutile
(Specimen No. 11)

Identification: Rutile is a titanium oxide, TiO It is red,
red-brown to black in color, with a yellow or pale
brown streak. The specific gravity is 4. 2 to 4. 3 and
the hardness from 6.0 to 6.5. In Florida, rutile occurs
as rounded sand-size particles.

Occurrence: Rutile is a heavy mineral in Florida's sands
and is found associated with ilmenite, zircon, stauro-
lite and others.

Production: Rutile is produced along with ilmenite in Clay,
Duval, and Indian River counties. The figures for
production and value of rutile are combined with those
of ilmenite.

Use: See "Ilmenite. "

24 FLORIDA GEOLOGICAL SURVEY

Figure 1,5. Rutile .

Zircon
(Specimen No. 12)

Identification: Zircon is a zirconium silicate, ZrSiO4.
Though commonly colorless, especially in Florida
sands, zircon may be red, blue, brown, or lavender.
The streak is colorless, the specific gravity 4.4 to

as sand-size particles and may be distinguished from
quartz by its brilliant luster and smooth crystal faces,
as seen with the aid of a microscope.

ZircOccurrence: Zircon is a heavy mineral in Florida's Recent
and ancient beach sands. No.

Identification: Zircon is prod u ced, along with other heavy
Thoughminerals, in Clay, Duvalorless, especand Indian River counties.
sands, zircon may be red, blue, brown, or lavender.
The streak is colorless, the specific gravity 4. 4 to
4. 8 and the hardness 7. 5. In Florida, zircon occurs
as sand-size particles and may be distinguished from
quartz by its brilliant luster and smooth crystal faces,
as seen with the aid of a microscope.

Occurrence: Zircon is a heavy mineral in Florida's Recent
and ancient beach sands.

Production: Zircon is produced, along with other heavy
minerals, in Clay, Duval, and Indian River counties.

SPECIAL PUBLICATION NO. 8

The production of zircon is over 30,000 short tons
annually, valued at more than $1 million.

Use: Zircon, because of its ability to withstand very high
temperatures, is made into bricks and cements used
in foundries and in furnaces for making aluminum and
glass. Zircon is a source of the metal zirconium,
which is used for flashlight powders, radio and tele-
vision tubes, electrodes, and as an alloy. Zirconium
steelis used in armor plate and in projectiles; zirco-
nium and nickel alloys are used in high speed cutting
tools and the oxide of zirconium, zirconia, is used
extensively in the manufacturing of ceramic glazes,
paints and porcelains.

Figure 16. Zircon.

FLORIDA GEOLOGICAL SURVEY

Staurolite
(Specimen No. 13)

Identification: Staurolite is a complex iron, aluminum sili-
cate, Fe"A14SiO 10(OH)2. It is usually some shade of
brown, has a colorless streak, a specific gravity that
ranges from 3. 4 to 3. 8 and a hardness of 7. 0 to 7. 5.
Staurolite resembles rutile under the microscope, but
has a dull luster. In Florida, staurolite occurs as
rounded sand-size particles.

Occurrence: Staurolite is one of the most abundant minerals
in Florida's heavy sand deposits.

Production: Staurolite is produced, along with other heavy
minerals, in Clay County. Estimated annual production
is about 20,000 short tons.

Use: The principal use of staurolite is in the production of
Portland cement, where it substitutes for clay in sup-
plying the necessary alumina and part of the iron as

-ei .
i I.-.
. . '

Figure 17. Staurolite.

SPECIAL PUBLICATION NO. 8

required by the cement formula. Staurolite is also
used as a sand blasting material.

Gypsum

Identification: The mineral gypsum is a hydrous calcium sul-
fate, CaSO4 2H20. It may be transparent to trans-
lucent when pure, but is often colored gray, yellow,

Figure 18. Gypsum and anhydrite.

red, brown or black by impurities. Gypsumhas white
streak, is soft enough to be scratched by a fingernail
(hardness of 2. 0), and has a low specific gravity (2. 2
to 2.4). Gypsum occurs in several forms, two of which
are knownto occur in the State. Selenite is a coarsely
crystalline, transparent variety composed of flat,
angular crystals that can be easily split apart. Massive
gypsum is a granular variety, showing no crystal form.

FLORIDA GEOLOGICAL SURVEY

Occurrence: Gypsum and anhydrite (closely related sulfate
minerals) are common minerals deep inthe subsurface
of the State. Small deposits of gypsum occur at the
surface in several localities in the peninsula. A de-
posit of very fine grained gypsum has been reported
from the east half of sec. 23, T. 20 S. R. 21 E. in
Sumter County. Crystals up to three-quarters of an
inch long have been reported at a depth of 4 feet from
a locality 3 miles east of Christmas in Orange County
and clear crystals up to 6 inches long have been dredged
from the Gulf of Mexico and Tampa Bay in Pinellas,
Pasco, and Hillsborough counties.

Production: No commercial deposits areknownto exist near
the surface in Florida, though deposits of commercial
extent are believed to be present at approximately 2,000
feet below the ground surface in Monroe County.

Use: When gypsum is heated and the water within it driven
off, it forms aplaster of Paris, which has the property
of becoming hard after being mixed with water. Plaster
of Paris is usedin wallplaster, plasterboard, stucco,
dentistry, crayons, casts and in many other ways.
Gypsum, when pulverized, is used as a fertilizer, and
it is also used as a flux in glass, ceramics, as a dis-
infectant and hardening retarder in cement.

Anhydrite
(Specimen No. 14)

Identification: Anhydrite is an anhydrous calcium sulfate,
CaSO4. It is closely related to the mineral gypsum,
but has a marble-like texture and usually shows no
crystal form. Anhydrite has a white, gray, or brown
color anda white streak and is distinguished from cal-
citebyits superior hardness of 3.0 to 3.5. The specific
gravity is 2. 89 to 2. 98.

Occurrence: Anhydrite occurs deep in the subsurface of the
State and is a common mineral seen in well cores.

SPECIAL PUBLICATION NO. 8

Use: Anhydrite serves nouse inthe State of Florida, although
in some states where it is nearer tothe ground surface
it finds use as a fertilizer and in the manufacture of
cement.

Phosphate Rock
(Specimen No. 15)

Identification: "Phosphate rock" is a general term applied
to natural deposits of minerals valued chiefly for their
phosphorous content. Phosphate rock is often called
phosphorite. However, it is essentially a carbonate
fluorapatite. The fluorapatite formula is Ca10Fz (PO4) 6.
The phosphate minerals are only discernible by X-ray
and the electron microscope. Phosphate rock is an
earthy material which varies from a hard rock to a
granular, loosely consolidated mass. The color may
be brown, gray, bluish gray, white, or black.

Occurrence: Florida's phosphate deposits are primarily of

Figure 19. Phosphate rock.

FLORIDA GEOLOGICAL SURVEY

the "land pebble" type, which represent marine rework-
ing of phosphatic limestones, and deposition of hard
pebbles of phosphate in a gravel bed. The land pebble
deposits occur in the Miocene, Hawthorn, and Bone
Valley formations, the latter of which is a gravel com-
posed of 10 to 20 percent phosphorite pebbles in a
mixture of sand, clay, and soft phosphate, along with
fossil teeth and bones of land and marine animals.
These deposits occur east of Tampa principally in Polk
and Hillsborough counties.

The minor hard-rock deposits are residual ac-
cumulations and redeposition of phosphate dissolved
from overlying phosphatic beds and deposited in lime-
stone by replacement. Hard-rock phosphate deposits
are mined in Citrus and Marion counties and are known
to occur in a general area extending from Suwannee to
Hernando counties, north-south.

Production: Florida isthe world's leading producer of phos-
phate rock, with over 10 million tons, valued at $70
million, mined yearly. This accounts for more than
24 percent of the total mineral production of the State.
Land pebble phosphate comprises the majority of
production with mines operating in Polk and Hills-
borough counties, although some hard-rock phosphate
is produced in Citrus County.

Use: Phosphate has a great many uses, the largest of which
is in the manufacture of phosphoric acid, superphos-
phate, triplesuperphosphate, ground rock and other
phosphatic salts for fertilizers. It also finds use in
explosives, soaps, medicine, ceramics, and many
other industrial commodities.

Peat
(Specimen No. 16)

Identification: Peat is an accumulation of partly decomposed
and disintegrated organic materials derived mainly
from woody parts of plants. It varies in consistency

SPECIAL PUBLICATION NO. 8

Figure 20. Peat.

from a fibrous, matted, turf-like material to a soft,
plastic mud. Peat exhibits no distinctive physical or
chemical properties by which it canbe easily identified,
other than its color and fibrous nature.

Occurrence: Peat occurs throughout the State wherever
swamp, bog or lowland conditions exist. The most
extensive deposits are in the Everglades, though peat
has been recovered commercially in Putnam, Orange,
Hillsborough, Polk, Bay and Broward counties.

Production: Peat is produced within the State only for local
use, and the mining operations are small. Over 39,000
short tons of peat, valued at more than $170,000 are
produced yearly.

FLORIDA GEOLOGICAL SURVEY

Use: Research has shownpeat tohave a great many potential
uses, though only one is presently utilized in the State.
The total State production is used in agriculture, but
other proven uses include use as a solid fuel and for
distilled products.

Fossils
(Specimen No. 17)

Fossils are the preserved remains or remnants of
ancient life, both plant and animal. Fossils are composed
of several mineral materials including calcite, aragonite,
silica, and a tough, horny material called chitin. Fossil
animal remains differ somewhat in composition from fossil
shells in that the original bone material has usually been
premineralized with silica, rather than by calcite.

Figure 21. Fossils.

SPECIAL PUBLICATION NO. 8

Fossils vary widely in relation to the ancient animals
of which they are remains. It is for this reason that their
study is confined somewhat to experts called paleontologists.
By identifying fossils, especially certain shellfish, they as-
sume a singular importance in that they can be used to date
and correlate various geologic formations, both state and
nationwide.

The remains of ancient life are abundant throughout
the State and can be found in great numbers in many places.

Figure 22. Prehistoric life.

FLORIDA GEOLOGICAL SURVEY

The best places tolookfor fossils are in quarries, road cuts
and especially the phosphate mines of central Florida. Here
a large portion of the material mined consists of the remains
of ancient animals which have accumulated over millions of
years.

Sea Shells
(Specimen No. 18)

Sea shells are the remains of marine life which have
accumulated through time and are still accumulating as
animals of the sea die or shed their hard protective cover-
ings. Shells vary widely in color and pattern and only their
biological features and shell composition are constant. The
shells are composed mainly of calcium carbonate, CaCO3,

Figure 23. Sea shells.

SPECIAL PUBLICATION NO. 8

but may consist of the mineral
aragonite, CaCO3, or a tough horny
material called chitin.

Production and use: Shells are
commercially valuable in that
marine animals, primarily
oysters, have built up shell
deposits in such great quan-
tities that they can be dredged
up from the water and used
for building roads, and for
agricultural purposes.

Shells are also of value to shell collectors andfor
the manufacture of shell jewelry and tourist goods.

Florida produces over 1. 1 million short tons of
oyster shell, valued at more than $2 million, annually.

OTHER ROCKS AND MINERALS OF FLORIDA

Agate and Chalcedony

Agate and chalcedony are composed of cryptocrystalline
silica, SiO2. They are known to occur in many parts of the
State, with one locality being world famous. Ballast Point,
Tampa Bay, Florida, is one of the few known places in the
world where agatizedpseudomorphs after coral may be col-
lected. Agatized fossils are found along the gulf coast and
in the phosphate mines of central Florida.

Aragonite

Aragonite possesses the same chemical composition
as calcite, CaCO3; only its crystal system and properties
are different. It is not as common as calcite, but is found in
the State, making up the shells of some Recent marine
animals.

FLORIDA GEOLOGICAL SURVEY

Figure 24. Dragline, land pebble phosphate mining.

Diatomaceous Earth (Diatomite)

Diatomite is made up of microscopic siliceous skeletons
of fresh water and marine creatures called diatoms. It re-
sembles chalk or clay, but is composed chiefly of silica.
Diatomite is found associated withpeat deposits in the State,
but has not been mined in recent years.

Pyrite

Pyrite (FeS) or "fools gold" is a brassy colored iron
sulfide. It occurs within the subsurface of the State in deep
well cores and has been found at one surface locality near
Ocala, Florida.

SPECIAL PUBLICATION NO. 8

Figure 25. Limestone quarry.

Vivianite

Vivianite is a rare iron phosphate, Fe3 (PO4) 2 8H2O,
which isfoundas earthy green masses or dark blue to green
crystals. Vivianite is known to occur inthe phosphate mines
at Mulberry, Florida, and possibly in others within the
phosphate mining area.

Mica

Mica is a complex aluminum silicate, KA13Si3 010(OH),
having a platy structure and occurring in small shiny flakes.
Mica is sometimes mistaken for gold in stream sediments
and certain rocks as it glistens brightly in sunlight. Mica is
recovered as a byproduct of kaolin processing in Putnam
County but serves no economic use in Florida.

FLORIDA GEOLOGICAL SURVEY

Petrified Wood

Although petrified wood is not of mineral origin, the
original wood has been replaced by silica (SiO2) in solution

SILICA: SiOz
x V/ IN

CHO organic material (old wood)
::CiO oranic material (old wood)

or more rarely by clay minerals. Petrified wood is often
found in the excavations for phosphate near Bartow, Florida,
and in the dredging operations of the southernportion of the
State.

Figure 26. Dredge, heavy minerals.

=_

SPECIAL PUBLICATION NO. 8

REFERENCES

Calver, James ;
1957

Carpenter, J. H
1953

L.

G

lining and mineral resources:
eol. Survey Bull. 39.

Florida

Mining and concentration of ilmenite and as -
sociated minerals at Trail Ridge, Florida:
Florida Geol. Survey Misc. Rept. 10.

Davis, John H. Jr.
1946 The peat deposits of Florida, their occur-
rence, development and uses: Florida Geol.
Survey Bull. 30.

Fenton, C.L.
1940 (and Fenton, M. A.) The rock book: New
York, Doubleday, Doran and Company.

Hurbut, C.S., Jr. (Editor)
1959 Dana's manual of mineralogy: 18th edition,
John Wiley and Sons, New York.

Manchester, James G.
1941 Collecting semiprecious stones in Florida:
Florida Geol. Survey Misc. Rept. 31.

Pearl, R.M.
How to know the minerals and rocks: New
American Library, New York (paper bound).

1956 Rocks and minerals: Barnes and Nobles,
New York.

Pough, F.H.
1953 A field guide to rocks and minerals: Houghlin
Mifflin, Boston.

U.S. Bureau
1949

of Mines
Titanium minerals in central and north-
eastern Florida: Rept. Inv. 4515.

FLORIDA GEOLOGICAL SURVEY

1956 Recovery of kyanite and sillimanite from
Florida beach sands: Rept. Inv. 5274.

Vernon, Robert O.
1943 Florida mineral industry, with summaries
of production for 1940 and 1941: Florida
Geol. Survey Bull. 24.

1951 Geology of Citrus and Levy counties, Florida:
Florida Geol. Survey Bull. 33.

Zimm, Herbert S.
(and Shaffen, P. R. ) Rocks and minerals:
Golden Nature Series, New York.

Zumberge, J. H.
1958 Elements of geology: John Wiley & Sons,
New York.

SPECIAL PUBLICATION NO. 8

B-- LIMESTONE, DOLOMITE,MARL AND
COQUINA
SAND AND OTHER MINERALS

j SAND, SHELL AND CLAY

SSAND, CLAY AND FULLER'S EARTH

GEOLOGIC DISTRIBUTION
OF ECONOMICALLY VALUABLE
SEDIMENTS IN FLORIDA

MILLISECOND	CLASS.METHOD	MESSAGE
0	sobekcm_page_globals.constructor
0	sobekcm_page_globals.constructor	Application State validated or built
0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.constructor	Navigation Object created from URI query string
0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.display_item	Retrieving item or group information
0	sobekcm_page_globals.get_entire_collection_hierarchy	Retrieving hierarchy information
0	sobekcm_assistant.get_entire_collection_hierarchy
0	cached_data_manager.retrieve_item_aggregation
0	cached_data_manager.retrieve_item_aggregation	Found item aggregation on local cache
0	item_aggregation_builder.get_item_aggregation	Found 'all' item aggregation in cache
0	system.web.ui.page.page_load (ufdc.page_load)
0	sobekcm_page_globals.constructor.on_page_load
0	html_echo_mainwriter.add_style_references	Adding style references to HTML
0	html_echo_mainwriter.add_text_to_page	Reading the text from the file and echoing back to the output stream
2	html_echo_mainwriter.add_text_to_page	Finished reading and writing the file

MILLISECOND

CLASS.METHOD

MESSAGE

sobekcm_page_globals.constructor

Application State validated or built

sobekcm_database.verify_item_lookup_object

sobekcm_page_globals.constructor

Navigation Object created from URI query string

sobekcm_database.verify_item_lookup_object

sobekcm_page_globals.display_item

Retrieving item or group information

sobekcm_page_globals.get_entire_collection_hierarchy

Retrieving hierarchy information

sobekcm_assistant.get_entire_collection_hierarchy

cached_data_manager.retrieve_item_aggregation

Found item aggregation on local cache

item_aggregation_builder.get_item_aggregation

Found 'all' item aggregation in cache

system.web.ui.page.page_load (ufdc.page_load)

sobekcm_page_globals.constructor.on_page_load

html_echo_mainwriter.add_style_references

Adding style references to HTML

html_echo_mainwriter.add_text_to_page

Reading the text from the file and echoing back to the output stream

html_echo_mainwriter.add_text_to_page

Finished reading and writing the file

	Title Page
	Letter of transmittal
	Preface
	Table of Contents
	Introduction
	Specimens in the sample set
	Other rocks and minerals of...
	References