Florida State Mineral
Calcite STATUS Unofficial DESCRIPTION One of the most common minerals on earth, calcite composes four to five percent of the Earth’s crust. It is a calcium carbonate that varies greatly in form and color. It is most often white or colorless, but impurities can color it pale shades of gray, yellow, red, green, blue, and even black, brown, or more than one color. These impurities include iron, magnesium, or manganese, and occasionally zinc and cobalt. Calcite readily effervesces in hydrochloric acid and dissolves in most other forms of acid and even in groundwater. The minerals aragonite and vaterite are polymorphs of calcite, which means all three share the same chemistry but not the same crystal structure. Of these minerals, calcite is the most stable. Calcite sometimes fluoresces, is transparent to opaque, and is birefringent, meaning it displays double refraction. The transparency of Iceland spar, a colorless variety of calcite, makes it useful in the optical field. The most common variety of calcite is a scalenohedron that appears as a double pyramid. A scalenohedron is a crystal of eight or 12 faces, each face being a scalene triangle. This variety is also called the dogtooth spar. STATE SYMBOL West central Florida has substantial limestone deposits, from Jefferson County south almost to Tampa. Calcite occurs in large clusters underground or underwater in pockets in the limestone. Although calcite is not mined commercially, Florida limestone quarries often unearth some handsome specimens of the mineral. Florida does not have an official state mineral, but calcite represents the state’s geology well. NAME ORIGIN The word "calcite" comes from the Latin word for lime, calx. FORMATION AND OCCURRENCE Calcium carbonate, from which calcite is formed, is the principal component of sedimentary rocks, especially limestone. It forms by surface precipitation and groundwater in oceans, lakes, and rivers. Approximately 10 percent of sedimentary rock is limestone. Organic sedimentary rocks are composed of the shells of dead marine organisms. Calcite also occurs in metamorphic marble, as a vein mineral in deposits from hot springs, and in caverns as stalagmites and stalactites. The mineral may also be found in volcanic and mantle rocks. GEOGRAPHIC DISTRIBUTION Calcite is abundant worldwide. A few notable localities are listed here. Iceland: Helgustadanáma mine, Reydarfjord United Kingdom: Alston Moor, Egremont, and Frizington, Cumbria; Weardale, Durham; and Liskeard, Cornwall; England Germany: St. Andreasberg, Harz Mountains, and Freiberg, Saxony Romania: Herja (Kisbánya), Baia Mare (Nagybánya) district United States: Rossie and Balmat, St. Lawrence County, New York; Hancock, Houghton County, Michigan; Phoenix mine, Keeweenaw County, Michigan; many mines in Reynolds County, Missouri; Joplin, Jasper County, Missouri; Galena, Cherokee County, Kansas; and Picher, Ottawa County, Oklahoma; Elmwood mine, near Carthage, Smith County, Tennessee; Bisbee, Cochise County, Arizona Mexico: Santa Eulalia and Areponapuchic Canyon, Chihuahua; many mines at Guanajuato; Charcas, San Luis Potosí Russia: Dal’negorsk, Primorskiy Krai Namibia: Tsumeb D.R. Congo: Mupine mine, Katanga Province USES Calcite is the primary ore of calcium, the main component of chalk, a major constituent of marble, and the base of cements and mortars. Calcite is important in the production of lime and in the manufacture of paint, glass, rubber, fertilizers, and many pharmaceuticals. Calcite has many applications in the chemical and optical fields. Its diversity and beauty make it one of the most collected minerals. FAMOUS EXAMPLES Since calcite is so common, large crystals are not considered very rare. The largest crystal of calcite was reportedly found in Helgustadir, Iceland. It is 23 feet by 23 feet by 6.6 feet (7x7x2 m).	Large Calcite Sample Showing Refractive Properties Calcite and Fluorite Orange Calcite and Amethyst Calcite Crystal on Rock CALCITE FACTS Group: Carbonate Chemical Formula: CaCO3 Crystal Structure: Trigonal hexagonal Hardness (Mohs): 3 Color: Colorless or white, also gray, yellow, green Transparency: Transparent, translucent Luster: Vitreous, pearly Density: 2.7102(2) g/cm3 Streak: White Cleavage: Perfect on {1011}. Fracture: Irregular/uneven, step-like Tenacity: Brittle
	Some data courtesy of the Mineralogical Society of America Author: World Trade Press