mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: White to pale yellow/honey; 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 pale yellow/honey
Luster: Vitreous to pearly

Identified May 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed through sedimentary precipitation in marine environments, hydrothermal veins, or as a primary mineral in igneous carbonatites. It is the main component of limestone and marble.

Uses & applications

Used in the manufacture of cement and mortar, as a soil conditioner in agriculture, in the optical industry (high-grade transparent specimens), and as a calcium supplement.

Geological facts

Calcite is famous for its double refraction (birefringence); if you look through a clear crystal, images appear doubled. It also reacts vigorously with dilute hydrochloric acid, producing carbon dioxide gas bubbles.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper penny but not a fingernail) and rhombohedral cleavage planes. Commonly found in limestone quarries, cave systems (stalactites), and hydrothermal ore veins.