calcium carbonate

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calcium carbonate,

CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. Calcium carbonate is largely insoluble in water but is quite soluble in water containing dissolved carbon dioxide, combining with it to form the bicarbonate Ca(HCO3)2. Such reactions on limestonelimestone,
sedimentary rock wholly or in large part composed of calcium carbonate. It is ordinarily white but may be colored by impurities, iron oxide making it brown, yellow, or red and carbon making it blue, black, or gray. The texture varies from coarse to fine.
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 (which is mainly composed of calcite) account for the formation of stalactites and stalagmites in caves. Iceland spar is a pure form of calcium carbonate and exhibits birefringence, or double refractionrefraction,
in physics, deflection of a wave on passing obliquely from one transparent medium into a second medium in which its speed is different, as the passage of a light ray from air into glass.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Calcium Carbonate

 

CaCO3, a salt.

Calcium carbonate occurs in nature in two mineral forms with differing crystalline structures: aragonite and the widely distributed calcite. Calcium carbonate decomposes when heated above 900°C: CaCO3 = CaO + CO2 (a means of obtaining lime). It is sparingly soluble in water (14 mg calcite per liter at 18°C) and readily soluble in acids. Natural calcium carbonate (limestone, marble) is used as a construction material; chalk (powdered calcium carbonate) serves as a filler for rubber stock, paper, and linoleum. A softer and finer product, called precipitated calcium carbonate (obtained through the reaction of CaCl2 and Na2CO3), is used in the manufacture of tooth powderand cosmetics.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

calcium carbonate

[′kal·sē·əm ′kär·bə‚nāt]
(inorganic chemistry)
CaCO3 White rhombohedrons or a white powder; occurs naturally as calcite; used in paint manufacture, as a dentifrice, as an anticaking medium for table salt, and in manufacture of rubber tires.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

calcium carbonate

A low-density white pigment for use in paint; provides little opacity; used mainly to provide bulk and flatness.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

calcium carbonate

a white crystalline salt occurring in limestone, chalk, marble, calcite, coral, and pearl: used in the production of lime and cement. Formula: CaCO3
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005