mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: Typically white or colorless, but can be any color; Luster: Vitreous to pearly; Crystal structure: Trigonal (often appearing as rhombohedral or scalenohedral crystals); Cleavage: Perfect rhombohedral in three directions; Specific gravity: 2.71

Hardness: 3 (Mohs scale)
Color: Typically white or colorless, but can be any color
Luster: Vitreous to pearly

Identified March 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed through both chemical precipitation and biological activity. It occurs in sedimentary environments as limestone and chalk, in metamorphic environments as marble, and in hydrothermal veins. It can form at any geological age, from Precambrian to modern-day deposits.

Uses & applications

Extensively used in construction as an ingredient in cement and mortar, as a soil conditioner in agriculture, as an abrasive, and in the chemical industry for acid neutralization. High-purity specimens are used in optical instruments (Iceland Spar).

Geological facts

Calcite is famous for its double refraction (birefringence), where light passing through a clear crystal splits into two rays, causing objects viewed through it to appear doubled. It is the primary component of stalactites and stalagmites found in caves.

Field identification & locations

Identify in the field by its rhombohedral cleavage and its vigorous reaction (effervescence) when touched with cold dilute hydrochloric acid. It is commonly found in limestone quarries, marble deposits, and mineral veins worldwide.