mineral

Calcite

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

Formed through sedimentary precipitation in marine environments, hydrothermal veins, or as a primary mineral in igneous carbonatites; can also be metamorphic (marble). Found in rocks of all geological ages.

Uses & applications

Used as an additive in cement and mortar, as a soil conditioner in agriculture, in the production of lime, as a white pigment, and in optical instruments (Iceland Spar).

Geological facts

Calcite exhibits double refraction, where light passing through it splits into two rays, making objects appear doubled. It is the primary component of limestone and marble.

Field identification & locations

Easily identified in the field by its 3-way rhombohedral cleavage and its vigorous effervescence (fizzing) when coming into contact with dilute hydrochloric acid or vinegar.