In 1979 the Florida Legislature designated agatized coral as the Florida State Stone. It is described in the statute as “a chalcedony pseudomorph after coral, appearing as limestone geodes lined with botryoidal agate or quartz crystals and drusy quartz fingers, indigenous to Florida.” See below to discover the rocks and minerals of Florida. To view information about Florida's geologic formations, visit Formations page.
| Type | Photo | Description |
|---|---|---|
| Sand | A loose, unconsolidated material of grain size between 0.08 mm and 2 mm, frequently composed of quartz. | |
| Gravel | Unconsolidated material larger than 2 millimeters in diameter, frequently composed of quartz. | |
| Common Clay | Material smaller than 0.08 millimeters in diameter, most often made up of clay minerals. | |
| Fullers Earth | Fullers Earth is the name applied to certain clays that have the ability to absorb coloring matter from vegetable, mineral and animal oils. | |
| Kaolin | Composed primarily of the clay mineral kaolinite, it can be white to grayish yellow in color, and is most commonly used for porcelain. | |
| Peat | An accumulation of partly decomposed and disintegrated organic materials derived mainly from woody parts of plants | |
| Sandstone | A sedimentary rock commonly composed of quartz sand grains cemented together by silica, calcite, iron oxide or other mineral substance. | |
| Limestone | A sedimentary rock composed of cemented calcite, fossil fragments and biogenic material. | |
| Dolostone | A sedimentary rock that formed from the replacement of Mg for Ca in limestones. | |
| Coquina | A type of limestone made up almost entirely of cemented shell fragments. | |
|
Agate |
A variety of cryptocrystalline quartz (SiO2). It is found in a variety of colors, typically gray, brown, black, white and sometimes red. Fossil corals and mollusks may be replaced with agate deposited by silica-rich ground water percolating through limestone. | |
|
Chert |
An extremely fine-grained variety of the mineral quartz. It is characterized by its extreme hardness (7.0) and glass-like fracture. | |
| Silicified Wood | The original wood has been replaced by silica (SiO2) in solution or more rarely by clay minerals. Often the fine details of the original tree bark are preserved. |
| Mineral | Photo | Description | Hardness | Specific Gravity |
|---|---|---|---|---|
| Anhydrite | An anhydrous calcium sulfate (CaSO4); closely related to gypsum but has a marble-like texture and usually shows no crystal form. | 3.0-3.5 | 2.89-2.98 | |
| Aragonite | A form of calcium carbonate, CaCO3, it is most frequently found as a component of bivalve shells. | 3.5-4 | 2.95 | |
| Calcite | A form of calcium carbonate, CaCO3, it varies in color. Distinguished from dolomite by its effervescence in cold dilute hydrochloric acid. | 3.0 | 2.7 | |
| Dolomite | A carbonate mineral, (Ca,Mg)[CO3]2, it is distinguished from calcite by crystalline structure (it often breaks up readily into crystals called rhombohedrons). | 3.5-4.0 | 2.85-2.95 | |
| Fluorapatite (Phosphate Rock) |
Often called phosphorite, fluorapatite, Ca10F2(PO4)6, is discernible only by X-ray or electron microscope. The color may be brown, gray, bluish gray, white or black. | 5.0 | 3.1-3.2 | |
| Gypsum | A hydrous calcium sulfate, CaSO4.2H2O. It has a white streak and is soft enough to be scratched by a fingernail. | 2.0 | 2.2-2.4 | |
| Illmenite | An iron, titanium oxide, FeTiO3, it is black to brownish black in color with a black to brownish red streak. | 5.0-6.0 | 4.3-5.5 | |
| Monazite | A complex yellow to reddish-brown natural phosphate of the rare earth elements: (Ce,La,Nd,Th)PO4. | 5.0-5.5 | 4.6-5.7 | |
| Pyrite | An iron mineral, FeS2, with a yellow metallic luster, it is often found as flecks in limestones | 6.0-6.5 | 5.0-5.2 | |
| Quartz | A crystalline form of silica, SiO2, it may be of any color, though the streak is always white. | 7.0 | 2.65 | |
| Rutile | A titanium oxide, TiO2, it is red, red-brown to black in color, with a yellow or pale brown streak. | 6.0-6.5 | 4.2-4.3 | |
| Staurolite | A complex iron, aluminum silicate, Fe2Al9Si4O22(OH)2, it is usually some shade of brown and has a colorless streak. | 7.0-7.5 | 3.4-3.8 | |
| Zircon | A zirconuim silicate, ZrSiO4, it may be colorless, red, blue, brown or lavender. The streak is colorless. | 7.5 | 4.4-4.8 |
For further information, please see the Guide to Rocks and Minerals of Florida (FGS Special Publication No. 8). This guide was first printed in 1961 and reprinted in 1981, and it currently is not available in printed form. Because of the age of this publication, some of the information is outdated.
This guide was written to serve as a tool for the identification, occurrence, production and use of Florida's most common rocks and minerals. It was primarily intended to be a simplified general reference for the student; therefore, technical information and detailed descriptive material were minimized. Some of the terminology used in these webpages (color, streak, hardness, specific gravity, cleavage) is explained in the guide.
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