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Calcite (CaCO3) is a soft carbonate mineral that occurs in various colors, including white, yellow, brown, gray, black, and pink, and also can be colorless. Calcite is a common mineral that occurs primarily in limestone and dolostone, occasionally in concretions and rarely as an efflorescence.

Chemical class: Carbonate

Crystallization: Hexagonal (trigonal); ditrigonal scalenohedral; 3m

Habit: Commonly well crystallized; scalenohedral and rhombohedral forms most common; commonly granular or massive.

Physical properties: Cleavage: {1011} perfect rhombohedral. Hardness: 3. Specific Gravity: 2.7. Luster: vitreous. Color: white, colorless, yellow, brown, gray, black, and pink. Streak: white. May be fluorescent. Effervesces vigorously in cold dilute hydrochloric acid.

Occurrence: Crystals and granular aggregates in cavities and fractures of dolostones and limestones in western Ohio; granular aggregates commonly form veins in dolostone concretions and less commonly in ironstone concretions from black shales in central and eastern Ohio; more rare as an efflorescence.

Additional Information

Bulletin 69: Minerals of Ohio - To order, contact the Geologic Records Center.