Calcite

Physical Properties

Hardness: 3 on Mohs scale; Color: White to colorless (transparent/translucent); Luster: Vitreous to pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific gravity: 2.71

Formation & Geological History

Primarily forms through chemical precipitation in marine environments or as a secondary mineral in igneous and metamorphic rocks. It is basic to the formation of limestone and marble.

Uses & Applications

Used widely in the construction industry as an ingredient in cement and mortar, in agriculture for soil treatment, as a pigment, and occasionally as a gemstone or ornamental stone.

Geological Facts

Calcite exhibits double refraction; if you look through a transparent crystal, objects behind it appear doubled. It is also the primary component of stalactites and stalagmites in caves.

Field Identification & Locations

Identify in the field by its rhombohedral cleavage and its strong reaction (effervescence) to dilute hydrochloric acid. It is found globally in sedimentary basins and limestone quarries.

Identified on: 4/28/2026

Mode: Standard