mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Pale yellow, white, or colorless; Luster: Vitreous to pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions.

Hardness: 3 on Mohs scale
Color: Pale yellow, white, or colorless
Luster: Vitreous to pearly

Identified July 4, 2026More mineral →

Explore Calcite in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3 on Mohs scale; Color: Pale yellow, white, or colorless; Luster: Vitreous to pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions.

Formation & geological history

Forms in sedimentary environments through chemical precipitation from calcium-rich water, or in metamorphic environments as marble. It is a primary constituent in limestone.

Uses & applications

Used in the manufacture of cement and mortar, as an agricultural soil treatment, in the pharmaceutical industry (antacids), and as a decorative stone or mineral specimen.

Geological facts

Calcite is famous for its double refraction property; when you look through a clear crystal, images appear doubled. It also reacts vigorously (fizzes) when it comes into contact with weak acids like vinegar.

Field identification & locations

Can be identified in the field by its 3-way rhombohedral cleavage (looks like a slanted cube) and its softness (can be scratched by a copper penny or a knife). Found globally in sedimentary basins.