calcite

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calcite Very common, widespread, rock-forming carbonate mineral, one of two polymorphs of CaCO3, the other being aragonite; sp. gr. 2.7; hardness 3; trigonal; usually colourless or white, but may be shades of yellow, grey, green, red, or even brown or black; white streak; vitreous lustre; crystals common, often tabular, prismatic, or rhombohedral, but fibrous aggregates and granular masses may also occur; cleavage perfect rhombohedral {101̄}; cleavage rhombs exhibit double refraction; a major constituent of calcareous sedimentary rocks, e.g. marbles. Calcite can be precipitated from sea water and is a common constituent of invertebrate shells, and late-stage hydrothermal solutions (see HYDROTHERMAL ACTIVITY) may precipitate calcite in cavities in some igneous rocks such as basalts. It is soluble in dilute hydrochloric acid. It is used as a flux, in cement-making and fertilizers, and as a building stone. See also CARBONATES.

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calcite (kăl´sīt), very widely distributed mineral, commonly white or colorless, but appearing in a great variety of colors owing to impurities. Chemically it is calcium carbonate, CaCO3, but it frequently contains manganese, iron, or magnesium in place of the calcium. It crystallizes in the hexagonal system, its crystals being characterized by highly perfect cleavage. Calcite also occurs in a number of massive forms, in which it may be coarsely to finely granular (as in marble), compact (as in limestone), powdery (as in chalk), or fibrous. One crystalline form, called dogtooth spar because of its dogtooth appearance, exhibits faces of perfect scalene triangles. Another form, satin spar, is finely fibrous and has a satin luster. Iceland spar is clear, transparent calcite. Other important forms of the mineral are limestone, marble, chalk, marl, stalactite and stalagmite formations, travertine, and Oriental alabaster. Millions of tons of calcite, in the form of limestone and marble, are mined annually. Besides its use as a building stone, it is the raw material for quicklime and cement, and is used extensively as a flux in smelting and as a soil conditioner.

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cal·cite / ˈkalˌsīt/ • n. a white or colorless mineral consisting of calcium carbonate. It is a major constituent of sedimentary rocks, can occur in crystalline form, and may be deposited in caves to form stalactites and stalagmites. DERIVATIVES: cal·cit·ic / kalˈsitik/ adj.

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calcite A very common form of calcium carbonate (CaCO3) that is the principal ingredient of many sedimentary rocks (e.g. limestones, marble, and chalk).

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calcite A very common form of calcium carbonate (CaCO3) that is the principal ingredient of many sedimentary rocks (e.g. limestones, marble, and chalk).