mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: White to colorless with brownish crust; 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 to colorless with brownish crust
Luster: Vitreous to pearly

Identified June 18, 2026More mineral →

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Physical properties

Formation & geological history

Forms through chemical precipitation in sedimentary environments, hydrothermal veins, or as a constituent of metamorphic marble. This specimen appears to be a vein filling or a crust formed from mineral-rich water.

Uses & applications

Used in the manufacture of cement and mortar, as a soil conditioner in agriculture, in the optical industry (high-quality crystals), and as a common mineral specimen for collectors.

Geological facts

Calcite is one of the most common minerals on Earth. It is the primary component of limestone and marble. It exhibits double refraction, where an image seen through a clear crystal appears doubled.

Field identification & locations

Can be identified in the field by its extreme softness (can be scratched by a copper coin) and its effervescence (fizzing) when in contact with dilute hydrochloric acid or vinegar. Found worldwide in sedimentary basins.