mineral

Calcite crystal cluster (likely stalactitic or vein calcite)

Calcite, calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

White to translucent, pearly-to-glassy luster with elongated bladed/fibrous crystals; Mohs hardness 3, perfect rhombohedral cleavage, trigonal crystal system, and specific gravity about 2.71. Brown areas likely iron-oxide or clay inclusions, possibly with minor sulfide or carbonate minerals.

Identified September 9, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal veins, cavities, caves, and sedimentary limestone environments when calcium-rich fluids precipitate carbonate. Its exact geological age cannot be determined from the image; the fibrous growth may represent layered or stalactitic deposition.

Uses & applications

Common calcite is used in cement, lime, aggregate, glass manufacture, and soil treatment; attractive crystals are collected. It is generally not used as a gemstone because of low hardness and cleavage.

Geological facts

Calcite effervesces vigorously with dilute hydrochloric acid and commonly shows double refraction. It can fluoresce under ultraviolet light depending on impurities.

Field identification & locations

Identify it by its softness, rhombohedral cleavage, acid reaction, and often curved or bladed crystal habits; common worldwide in limestone districts and hydrothermal deposits. The specimen may be associated with quartz, clay, iron oxides, or sulfides.