mineral

Calcite crystal cluster

Calcite, calcium carbonate (CaCO3)

AI-generated identification · may be incorrect

White to colorless, vitreous to pearly luster, transparent to translucent, and commonly forms rhombohedral crystals with perfect rhombohedral cleavage. Mohs hardness 3; specific gravity about 2.71. The blocky, slanted cleavage faces strongly favor calcite over quartz.

Identified September 2, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal veins, limestone cavities, caves, and sedimentary environments through precipitation from calcium-rich fluids; specimens may range from recent growth to Paleozoic or younger host-rock ages. Exact age and locality cannot be determined from the photograph.

Uses & applications

Used industrially for cement, lime, aggregate, soil neutralization, and chemical manufacture; clear crystals are collected and occasionally used as optical specimens or decorative pieces. This cluster is primarily a mineral specimen rather than a construction stone.

Geological facts

Calcite effervesces vigorously with dilute hydrochloric acid or vinegar, especially when powdered or freshly scratched. It shows strong birefringence: text viewed through a clear cleavage fragment appears doubled.

Field identification & locations

Identify by its rhombohedral cleavage, low hardness, and acid reaction; it can be scratched by a copper coin or steel knife. Common localities include Mexico, Iceland, England, the United States, and many limestone districts.