mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 (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 (Mohs scale)
Color: White, colorless
Luster: Vitreous to pearly

Identified June 9, 2026More mineral →

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Physical properties

Hardness: 3 (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 as chemical precipitates from evaporating seawater or through biological activity (shells/skeletons). It is also found in metamorphic marble and igneous carbonatites.

Uses & applications

Used in the manufacture of cement and mortar, as a soil conditioner in agriculture, in the optical industry (high-quality clear crystals), and occasionally as a decorative stone.

Geological facts

Calcite exhibits the property of double refraction; if you look through a clear crystal, images appear doubled. It is the primary component of limestone and marble.

Field identification & locations

Identify in the field by its rhombohedral cleavage (slanted cubes) and its strong reaction (fizzing) when exposed to dilute hydrochloric acid or vinegar. Found worldwide in sedimentary basins.