mineral

Calcite

Calcium Carbonate (CaCO3)

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

Hardness: 3 on Mohs scale
Color: Colorless, white, or beige/tan
Luster: Vitreous to pearly

Identified June 28, 2026More mineral →

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Physical properties

Formation & geological history

Commonly forms in sedimentary environments through chemical precipitation or as biogenic remains in marine settings. It can also form in hydrothermal veins and metamorphic rocks like marble.

Uses & applications

Used as an industrial mineral for neutralizing acids, as a cleaning agent, in chromatography, for optical purposes (Iceland Spar), and in the production of cement and lime for construction.

Geological facts

Calcite exhibits double refraction; if you place a clear piece over a printed line, the line will appear doubled. It is the primary component of stalactites and stalagmites found in caves.

Field identification & locations

Identify in the field by its rhombohedral shape and its intense effervescence (fizzing) when a drop of dilute hydrochloric acid or vinegar is applied. It can be found globally in limestone and marble quarries.