mineral

Calcite crystal cluster

Calcite — calcium carbonate, CaCO₃

AI-generated identification · may be incorrect

White to colorless, vitreous to pearly luster, commonly rhombohedral or scalenohedral crystals; Mohs hardness 3, perfect rhombohedral cleavage, and specific gravity about 2.71. The specimen appears to be a rough cluster of intergrown translucent calcite crystals.

Identified September 5, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal veins, limestone cavities, caves, and sedimentary deposits when calcium-rich fluids precipitate carbonate minerals. It may range from modern cave growth to Paleozoic or younger host-rock mineralization; age cannot be determined from the image.

Uses & applications

Used extensively in cement, lime, construction aggregate, glass, agriculture, and chemical manufacture; attractive transparent crystals are collected but are generally inexpensive.

Geological facts

Calcite strongly effervesces with dilute hydrochloric acid and displays birefringence, producing a doubled image through clear pieces. Its crystal shapes and cleavage distinguish it from quartz.

Field identification & locations

Common worldwide, especially in limestone regions, hydrothermal veins, and mines; notable localities include Mexico, Iceland, England, and the United States. Test gently with a steel blade for softness and use acid only on an inconspicuous area.