mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: typically white or colorless, but can be yellow, orange, or brown; Luster: vitreous to pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions.

Hardness: 3 on Mohs scale
Luster: vitreous to pearly

Identified April 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed through chemical precipitation in sedimentary environments, often in marine settings or through hydrothermal activity. It is the primary component of limestone and marble.

Uses & applications

Used in the manufacture of cement and mortar, as an agricultural soil neutralizer, in the pharmaceutical industry (antacids), and as a white pigment.

Geological facts

Calcite is famous for its optical property of double refraction (birefringence); if you look through a clear piece, objects behind it appear doubled. It also reacts vigorously and fizzes when exposed to weak acids like vinegar.

Field identification & locations

Identify in the field by its low hardness (can be scratched by a copper penny but not a fingernail) and its distinct rhombohedral cleavage. It is found globally, notably in the United States, Mexico, and Brazil.