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calcite
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A photograph of three fragments of calcite made up of one gray cube and two smaller transparent fragments. calcite crystal structure Diagram showing several shapes of natural calcite crystals. The top section illustrates four untwinned crystal habits, each with different geometric forms. The bottom section displays two examples of twinned calcite crystals, highlighting how their structures differ. Red dashed lines and axes indicate symmetry and orientation. Steep white chalk cliffs rise sharply with sparse trees along the top edge on the eastern coast of Mon island, Denmark. calcite Zincite in white calcite from Franklin, N.J. Relations between lamellar twinning and cleavage planes in dolomite and calcite. This difference can be discerned best when thin sections of the minerals are viewed under a microscope. Diagram of double refraction: an unpolarized light ray enters a transparent calcite crystal and splits into a straight ordinary ray and an upward-bending extraordinary ray.
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Basalt sample returned by Apollo 15, from near a long sinous lunar valley called Hadley Rille. Measured at 3.3 years old.
(Bed) Rocks and (Flint) Stones
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A photograph of three fragments of calcite made up of one gray cube and two smaller transparent fragments.
Calcite is the most-abundant carbonate mineral in the world. It is primarily used in construction in cement and concrete. A large percentage of the calcite, the most abundant of these carbonate minerals, occurs in limestones, which constitute noteworthy proportions of many sequences of marine sediments.

calcite

mineral
Written by
R.V. Dietrich
Emeritus Professor of Geology, Central Michigan University, Mount Pleasant. Author of Stones; coauthor of Gems, Gravels and Granites.
R.V. Dietrich
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calcite, the most common form of natural calcium carbonate (CaCO3), a widely distributed mineral known for the beautiful development and great variety of its crystals. It is polymorphous (same chemical formula but different crystal structure) with the minerals aragonite and vaterite and with several forms that apparently exist only under rather extreme experimental conditions. The carbonate minerals calcite, aragonite, and dolomite have been calculated to make up approximately 15 percent of the Earth’s sediments and...

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