Iowa State Mineral
Calcite STATUS Unofficial DESCRIPTION One of the most common minerals on Earth, calcite makes up four to five percent of the Earth’s crust. It is a calcium carbonate that varies greatly in form and color. Calcite 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 acids 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. A colorless variety of calcite called Iceland spar is utilized in the optical field due to its transparency. 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 Calcite occurs in vugs (small to medium-sized cavities) in Iowa’s deposits of limestone and dolomite. The dogtooth spar variety is found in parts of Iowa. Calcite is also common in many of the state’s famous geodes. NAME ORIGIN The word "calcite" comes from the Latin word for mineral lime, calx. FORMATION AND OCCURRENCE Calcite sometimes occurs as limestone, an organic sedimentary rock that forms by surface precipitation and groundwater in oceans, lakes, and rivers. Approximately 10 percent of sedimentary rock is limestone. Organic sedimentary rocks such as limestone are composed of the shells of dead marine organisms. The shells are made up of calcium carbonate, which  accretes to make up the stone.   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; it is also the main component of chalk and of marble. Calcite is important in the production of lime for agriculture and industry. It has applications in the manufacture of paint, glass, rubber, fertilizers, and many pharmaceuticals and is the base of cements and mortars. 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).	Amber Colored Calcite Specimen Calcite Crystals Calcite and Fluorite Calcite and Amethyst 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