mineral

Calcite crystal specimen

Calcite — calcium carbonate, CaCO₃

AI-generated identification · may be incorrect

White to pale cream, translucent, with pearly-to-glassy luster and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. The stepped, blocky form and strong cleavage are characteristic, though the image cannot confirm crystal habit definitively.

Identified August 18, 2026More mineral →

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Physical properties

Formation & geological history

Forms when calcium-carbonate-rich groundwater precipitates in cavities, veins, caves, and sedimentary environments; some specimens grow in hydrothermal veins. Individual crystals may be geologically young, while host rocks can range from Paleozoic to modern.

Uses & applications

Used industrially for cement, lime, aggregate, soil treatment, and chemical manufacture; clear optical calcite is collected and occasionally used decoratively. This small rough specimen is mainly a teaching or collector piece.

Geological facts

Calcite effervesces vigorously with dilute hydrochloric acid or strong vinegar, unlike most look-alikes. It commonly shows double refraction and can fluoresce under ultraviolet light.

Field identification & locations

Common worldwide in limestone, marble, geodes, and mineral veins, especially Mexico, the United States, Iceland, and China. Confirm with a hardness test against a copper coin or steel knife and an acid reaction; avoid damaging valuable specimens.