mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Yellow, colorless, white, or various pastel shades; Luster: Vitreous to pearly; Crystal structure: Trigonal (rhombohedral); Cleavage: Perfect rhombohedral in three directions; Specific Gravity: 2.71

Hardness: 3 on Mohs scale
Color: Yellow, colorless, white, or various pastel shades
Luster: Vitreous to pearly

Identified July 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed in sedimentary, metamorphic, and igneous environments. Most commonly precipitated from water rich in calcium and carbonate ions, forming limestone, marble, and cave formations over millions of years.

Uses & applications

Used widely in construction materials (cement, concrete), agriculture (soil conditioning), manufacturing of paper, plastics, and optical equipment due to its strong birefringence.

Geological facts

Calcite is the primary constituent of limestone and marble. It exhibits strong double refraction (birefringence), meaning light passing through it splits into two separate rays, creating a doubled image.

Field identification & locations

Easily identified in the field by its characteristic rhombohedral cleavage and its vigorous effervescence (fizzing) when exposed to weak hydrochloric acid (HCl). Found worldwide.