mineral

Raw calcite specimen

Calcite (calcium carbonate, CaCO₃)

AI-generated identification · may be incorrect

Typically colorless to white or honey-colored, with vitreous to pearly luster, excellent rhombohedral cleavage, and Mohs hardness 3; crystals are trigonal. The cloudy, blocky cleavage surfaces and pale coloration fit calcite, though quartz or aragonite may occur as minor associates.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms from precipitation in limestone caves, hydrothermal veins, sedimentary carbonate beds, and metamorphic marbles. Individual crystals can form at any age, commonly from relatively young groundwater or hydrothermal activity.

Uses & applications

Used to manufacture cement, lime, agricultural soil conditioners, and fillers; transparent optical calcite is collectible. This rough specimen has modest display value unless crystals are unusually clear or well formed.

Geological facts

Calcite effervesces vigorously in dilute hydrochloric acid or strong vinegar, unlike quartz. Its rhombohedral cleavage can produce deceptively geometric fragments.

Field identification & locations

Common worldwide in limestone regions, including Mexico, the United States, Iceland, China, and Morocco. Test with a copper coin or knife cautiously, inspect cleavage, and apply acid only to a concealed spot.