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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.
..... Click the link for more information. (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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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.