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Calcium carbonate is a chemical compound with the chemical formula Ca CO 3. It is a common substance found in rocks as the minerals calcite and aragonite , most notably in chalk and limestone , eggshells , gastropod shells , shellfish skeletons and pearls .
Aragonite is the high pressure polymorph of calcium carbonate. As such, it occurs in high pressure metamorphic rocks such as those formed at subduction zones. [13] Aragonite forms naturally in almost all mollusk shells, and as the calcareous endoskeleton of warm- and cold-water corals (Scleractinia). Several serpulids have aragonitic tubes. [14]
Calcium carbonate (CaCO 3) and calcium sulfate (CaSO 4) are particularly abundant minerals. [19] Like strontium and barium, as well as the alkali metals and the divalent lanthanides europium and ytterbium , calcium metal dissolves directly in liquid ammonia to give a dark blue solution.
Vaterite, like aragonite, is a metastable phase of calcium carbonate at ambient conditions at the surface of the Earth. As it is less stable than either calcite, the most stable polymorph, [ 5 ] or aragonite, vaterite has a higher solubility than either of these phases.
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO 3).It is a very common mineral, particularly as a component of limestone.Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratch hardness comparison.
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Calcium peroxide or calcium dioxide is the inorganic compound with the formula CaO 2. It is the peroxide (O 2 2−) salt of Ca 2+. Commercial samples can be yellowish, but the pure compound is white. It is almost insoluble in water. [3]