mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: colorless to white/translucent; Luster: vitreous (glassy) to pearly; Crystal Structure: Trigonal (often found in rhombohedral cleavage fragments); Cleavage: Perfect in three directions.

Hardness: 3 on Mohs scale
Color: colorless to white/translucent
Luster: vitreous (glassy) to pearly

Identified July 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily through sedimentary processes by chemical precipitation from marine waters or through the accumulation of shell, coral, and algal debris. It can also occur as a vein mineral in igneous and metamorphic rocks.

Uses & applications

Used extensively in the manufacture of cement, lime, and glass; as a soil conditioner in agriculture; as a building stone (limestone/marble); and as specimens for mineral collectors.

Geological facts

Calcite is famous for its property of double refraction (birefringence). If you place a clear piece over a line on a paper, you will see two lines. It is also the primary component of limestone and marble.

Field identification & locations

The easiest field test is the acid test: calcite will effervesce (fizz) vigorously when in contact with weak hydrochloric acid or vinegar. Its rhombohedral shape and low hardness (can be scratched by a copper penny) are also key indicators.