mineral

Calcite crystal cluster

Calcite (calcium carbonate, CaCO₃)

AI-generated identification · may be incorrect

Typically colorless to cream/white, with glassy to pearly luster and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. The blocky, sparkling cleavage fragments are consistent with calcite, though image-only identification is not definitive.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Calcite commonly precipitates from groundwater, hydrothermal fluids, and sedimentary environments, forming veins, cavities, and limestone deposits. Individual specimens may be geologically young or millions to hundreds of millions of years old.

Uses & applications

Used to manufacture cement, lime, aggregate, and agricultural soil amendments; clear crystals are collected and occasionally used decoratively. This small cabinet specimen likely has modest commercial value.

Geological facts

Calcite effervesces vigorously with dilute hydrochloric acid and shows strong birefringence, producing doubled images through clear pieces. It is commonly confused with quartz, but calcite is much softer and cleaves readily.

Field identification & locations

Look for rhombohedral cleavage, low hardness, and acid reaction; quartz lacks cleavage and scratches glass. Common localities include Mexico, Iceland, the United States, China, and Morocco.