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FLORIDA'S

ROCKS

AND

MINERALS


'I cIt


FLORIDA GEOLOGICAL SURVEY
LEAFLET 19
COMPILED & UPDATED BY
J.M. LLOYD, P.A. BOND
& S.E. RAMDEEN

FLORIDA DEPARTMENT OF
ENVIRONMENTAL PROTECTION
FLORIDA GEOLOGICAL SURVEY
903 W. TENNESSEE STREET
TALLAHASSEE, FL 32304
(850) 488-9380
www.dep.state.fl.us/geology
2009






FLORIDA'S ROCKS

CHERT: Chert is also known as flint or flint rock and
is a deposit of microcrystalline silica. Florida's cherts
are generally gray in color, though some are bright
shades of blue, red, yellow and orange. It is
characterized by its extreme hardness and is found in
association with some of the limestone formations,
especially the Ocala. Florida's Native Americans used
chert in the manufacturing of axes, spear heads and
arrow points.

COMMON CLAY: Another sedimentary rock found
throughout Florida, common clay is sticky and is
composed primarily of varying amounts of clay
minerals, quartz sand, calcite, iron oxides, organic
impurities and other materials. Most of Florida's clay
was originally deposited as mud in seas, lakes, rivers or
deltas. The principal use of common clay in Florida is
as an addition to sand in the construction of roads.
Clays are also used in the manufacture of cement and
lightweight aggregate.

DOLOSTONE: Dolostone is a sedimentary rock that
is often associated with limestone deposits; it is
composed principally of the mineral dolomite
CaMg(CO3)2. The test for dolomite is the same as that
for calcite, except that dolomite effervesces very slowly
in cold dilute hydrochloric acid, and more vigorously in
warm acid. Dolostone is used for the same purposes as
limestone with the exception of cement manufacturing.

LIMESTONE: Various types of limestone underlie
all of Florida, but in many parts of the state, the
limestone is covered by the sand and clay that forms the
land surface. Limestone is a sedimentary rock
composed principally of the mineral calcite (CaCO3). It
may be easily identified by the application of a drop of
cold dilute hydrochloric acid, which causes the calcite
particles to effervesce freely. It is used for road base
material, concrete and asphalt aggregate, cement
manufacturing, fertilizer, soil conditioner and rip rap.

EXAMPLES OFLIMESTONE
FORMATIONS FOUND IN FLORIDA:

ANASTASIA FORMATION: The Anastasia
Formation is coquina, which is a limestone composed
of whole or broken shells and quartz sand grains that
are cemented together by calcite. Coquina has been
used as a building stone in Florida for over 400
years. It is found at land surface along the east coast
from St. Johns to Palm Beach Counties, but is rarely
found more than five miles inland.






KEY LARGO LIMESTONE: The Key Largo
Limestone is a hard, white to light gray rock which
contains numerous fossil corals. The Key Largo
Limestone extends on the surface from Soldier Key on
the north to the New Harbor Keys just south of Big Pine
Key.

MIAMI LIMESTONE: The Miami Limestone is a
soft to hard, recrystallized limestone. Near the east coast,
it is composed mainly of ooliths with some quartz sand
and fossils. Inland, it is a fossiliferous limestone with
some sand. Ooliths are small rounded grains that look
like fish eggs and are composed of layers of calcite
deposited around sand grains or fossil fragments. The
Miami Limestone is found at the surface in parts of
Broward, Collier, Dade and Monroe Counties.

OCALA LIMESTONE: Generally the Ocala
Limestone is soft and porous, but in places it is hard and
dense because of cementation of the particles by
crystalline calcite. The deposit is remarkable in that it is
composed of almost pure calcium carbonate: shells of sea
creatures and very tiny chalky particles. Ocala Limestone
underlies almost all of Florida, but it is found at the
surface of the land only in a small portion of the Florida
panhandle and northwestern peninsula.

SUWANNEE LIMESTONE: Not as pure as the
Ocala, Suwannee Limestone nevertheless contains a very
high percentage of calcium carbonate. The impurities in
the Suwannee (principally quartz sand and clay) may
amount to ten percent of the rock. The Suwannee is
usually harder and more compact than the Ocala.

PHOSPHATE ROCK: "Phosphate rock" is a general
term applied to natural deposits of minerals valued chiefly
for their phosphorus content. It is an earthy material which
varies from a hard rock to a granular, loosely consolidated
mass. Florida's phosphate deposits are primarily of the
"land pebble" type, which result from marine reworking of
phosphatic limestones and deposition of hard pebbles of
phosphate in gravel beds. Mining of this land pebble
phosphate occurs in central Florida in Hillsborough, Polk,
Manatee and Hardee Counties, making the state the nation's
leading producer of phosphate rock. Phosphate has a great
many uses, the largest of which is in the manufacture of
phosphoric acid, superphosphate, triple superphosphate,
ground rock and other phosphatic salts for fertilizer.

SANDSTONE: This is another 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
cementing agent, sandstones may be almost any color. 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. No commercial
use is made of Florida sandstone, though it has been
used on a very limited scale as a building stone.

FLORIDA'S MINERALS

ANHYDRITE: The mineral anhydrite is an
anhydrous calcium sulfate. 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 and a white streak. It is
harder than calcite and does not effervesce in
hydrochloric acid. Anhydrite can be used in fertilizer
and cement; however, it is not used commercially in
Florida.

CALCITE: The mineral calcite, which makes up
limestone, is composed of calcium carbonate
(CaCO3). It varies in color from white to colorless to
shades of yellow, orange or gray. It breaks up readily
into crystalline forms called rhombohedra and can be
identified by its effervescence in cold dilute
hydrochloric acid.

DOLOMITE: The mineral dolomite, CaMg(CO3)2,
is the principal component of the sedimentary rock
dolostone. Dolomite has a white, light brown or pink
color, with a white streak. The test for dolomite is the
same as that for calcite, except that dolomite
effervesces very slowly in cold dilute hydrochloric
acid, and more vigorously in warm acid.

FULLER'S EARTH: This name is applied to
certain clays that have the ability to absorb oil from
various materials. Generally, fuller's earth found in
Florida is light green or gray in color, has a greasy
feel when wet, and has low specific gravity. Sizable
deposits occur near the surface of the ground in
Gadsden and Marion Counties. Fuller's earth is used
in drilling mud, liquid fertilizer suspenders, paint
thickeners, medical drugs, absorbents, pet litter,
soaps, paints, polishes, plastics and other materials.

GYPSUM: The mineral gypsum is a hydrous
calcium sulfate. It may be transparent to translucent
when pure, but is often colored gray, yellow, red,
brown or black by impurities. It is soft enough to be
scratched by a fingernail and occurs in several forms,
two of which are known in Florida. 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. Gypsum and anhydrite (closely related
sulfate minerals) are common minerals deep in the






subsurface of the state. Gypsum is used in wall plaster,
wall board, stucco, crayons, casts, cement and
fertilizers. It is also used as a flux in glass and
ceramics, and as a disinfectant.

HEA VY MINERALS:

ILMENITE: The black to brownish mineral
ilmenite (iron titanium oxide) often has a black to
brownish red streak. Ilmenite is naturally slightly
magnetic, but the magnetism can be greatly increased
by heating. In Florida, ilmenite occurs as rounded,
sand-size particles. The chief use for the mineral
ilmenite is in the manufacturing of titanium oxide
pigment for white paints. Ilmenite is used for coating
electric welding rods and also as a source of titanium
metal.

STAUROLITE: Staurolite is a complex iron,
aluminum silicate mineral. It is usually a shade of
brown, has a colorless streak and occurs as rounded
sand-sized particles. Staurolite is abundant in
Florida's heavy-mineral sand deposits. Its principle
use is in the production of Portland cement where it
substitutes for clay in supplying the necessary
alumina and part of the iron required by the cement
formula.

RUTILE: Another titanium oxide mineral, rutile is
red, red-brown or black in color, with a yellow or
pale brown streak. It is or has been produced along
with ilmenite in Clay, Duval and Indian River
Counties. Its uses are the same as those for ilmenite.

ZIRCON: This is a commonly colorless zirconium
silicate mineral. In Florida, however, zircon may be
red, blue, brown or lavender with a colorless streak.
It occurs as sand-size particles in Florida and may be
distinguished from quartz by its brilliant luster and
smooth crystal faces, as seen with the aid of a
microscope. Zircon withstands very high
temperatures, making it suitable for use in bricks and
cements for foundries and furnaces. It is also a source
for the metal zirconium, which is used as an alloy for
various purposes.

KAOLIN: Kaolin is a soft, lightweight, often chalk-
like clay that has an earthy odor, and in Florida is
generally light in color and associated with large
amounts of quartz sand. The state reserve of kaolin
occurs in large deposits in the east-central part of the
state from southern Clay County to northern Highlands
County. A small deposit occurs in west Florida in a
narrow belt extending from Jackson County into Santa
Rosa County. High grade kaolin, called china clay, is







used to manufacture china, porcelain and ceramics. It is
also used as filler in paints, paper, soaps, toothpaste,
crayons, textiles and other products.

LIMONITE: Limonite, a compound of iron, oxygen and
hydrogen, is a yellowish brown to dark brown or black
mineral. 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.
Commercially, limonite is used as an ore for iron and as a
pigment in paints.

QUARTZ: In Florida, quartz primarily occurs in surface
deposits of unconsolidated small grain-sized sand particles.
Though common quartz sand is the most abundant surface
material in Florida, the deposits are not extensively
developed. Quartz sand is used for making glass and for
grinding and polishing metals. Other uses are as molding
sand, blast sand and fill material.

FURTHER READING

Campbell, Kenneth M., 1986, The Industrial Minerals of Florida:
Florida Geological Survey Information Circular No. 102, 94 p.;
http://www.uflib.ufl.edu/ufdc/?s fgs&m hd2J&i 74918

Lane, Ed (Editor), 1994, Florida's Geological History and
Geological Resources, Florida Geological Survey Special
Publication No. 35, 64 p.;
http://www.uflib.ufl.edu/ufdc/?b=UF00000124&v 00001

Lane, Ed, 1987, Guide to Rocks and Minerals of Florida: Florida
Geological Survey Special Publication No. 8, 61 p.;
www.dep.state.fl.us/geolog2/geologictopics/rocks rock minerals.pdf

Scott, Thomas M., 1992, A Geological Overview of Florida:
Florida Geological Survey Open File Report No. 50, 78 p.;
http://aquacomm.fcla.edu/1509/

Spencer, Steve, 1993, Industrial Mineral Operations of Florida:
Florida Geological Survey Map Series 139, Scale: 30 miles to 1
inch, http://purl.fcla.edu/fcla/ic/UF00015030

Spencer, Steve, 1999, Industrial Minerals Industry Directory of
Florida, Florida Geological Survey Information Circular No. 112,
26 p.; http://www.uflib.ufl.edu/ufdc/?s fgs&m hd2J&i 164410

Spencer, Steve and Rupert, Frank, 2003, Florida's Industrial
Minerals Making Modem Life Possible: Florida Geological
Survey Poster No. 9, Color, 22"X37";
http://www.dep.state.fl.us/geologv/images/Poster9.ipg