Calcite (Calcium Carbonate)
Sulfur with Calcite and Celestite on Dolomite, Attributed to Oak Harbor, Ottawa County, Ohio; N 5743
The name calcite comes from a Greek word meaning lime. This comes from its chemical component, Calcium Carbonate, which sometimes is mistakenly known as "lime." Calcite is known in more than 300 forms of crystals. The scalenohedral crystals of Calcite, one of its most common varieties, ordinarily are known as "dogtooth spar" or "dogtooth calcite" because of their resemblance to a dog's canine tooth.Another variety, transparent rhombohedral calcite, is used in optical equipment. Although they are not specific varieties of calcite, stalactites, stalagmites and other formations found in caverns are made of calcite.
Calcite is one of the most common minerals, making up about 4% by weight of the Earth's crust. Calcite is common as vein fillings in many rocks in western and central Ohio. Silurian dolomites in northwestern Ohio yield clusters of large crystals ranging from clear to dark brown. Many have a golden color.