mineral

Calcite fragment

Calcite, calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

Pale cream to honey-colored, translucent, with a vitreous to pearly luster and prominent rhombohedral cleavage; Mohs hardness 3, commonly effervesces strongly in dilute hydrochloric acid. The appearance suggests massive or cleaved calcite rather than a crystalline rock.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Calcite forms in sedimentary limestones, hydrothermal veins, caves, and as a cement in fractures; it occurs from ancient to modern geological settings. The specimen may be a weathered or cleaved piece of limestone-derived calcite.

Uses & applications

Used to manufacture cement and lime, as a flux and soil conditioner, and occasionally as a decorative or collecting specimen; transparent varieties are used for optical demonstrations rather than jewelry due to softness.

Geological facts

Calcite displays strong birefringence: clear pieces can produce doubled images. It is one of the most abundant carbonate minerals and a major component of limestone and marble.

Field identification & locations

Identify it by rhombohedral cleavage, low hardness, and acid fizz; distinguish it from quartz, which is harder and does not react with acid. Common worldwide, especially in carbonate rocks, caves, and mineral veins.