12 Mayıs 2013 Pazar

Iowa State Mineral

Iowa State Mineral


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.
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.
The word "calcite" comes from the Latin word for mineral lime, calx.
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.
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
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.
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).
State Mineral
Amber Colored Calcite Specimen
State Mineral
Calcite Crystals
State Mineral
Calcite and Fluorite
State Mineral
Calcite and Amethyst
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

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