mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: White/Colorless; Luster: Vitreous to pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific gravity: 2.71

Hardness: 3 on Mohs scale
Color: White/Colorless
Luster: Vitreous to pearly

Identified May 24, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale; Color: White/Colorless; Luster: Vitreous to pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific gravity: 2.71

Formation & geological history

Commonly forms in sedimentary environments through chemical precipitation or as a constituent of marine organisms. It is the primary component of limestone and marble. Can form across various geological ages.

Uses & applications

Used in the manufacture of cement and mortar, as a soil conditioner in agriculture, as an optical cleaner, and high-clarity specimens are used for scientific instrumentation.

Geological facts

Calcite is known for its property of double refraction (birefringence), where light passing through it splits into two rays. It is the primary mineral found in stalactites and stalagmites in caves.

Field identification & locations

Identify in the field by its rhombohedral cleavage and its strong reaction (effervescence) when touched with dilute hydrochloric acid. It can be scratched by a copper coin but not a fingernail.