mineral

Blue calcite cluster

Calcite (calcium carbonate, CaCO₃)

AI-generated identification · may be incorrect

Typically pale blue to gray-blue with vitreous to pearly luster, translucent edges, and prominent rhombohedral cleavage; Mohs hardness 3, trigonal crystal system, specific gravity about 2.71. The specimen appears to be a cluster of intergrown, cleaved calcite crystals.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Forms in limestone cavities, hydrothermal veins, and carbonate-rich sedimentary environments when calcium-bearing fluids precipitate calcite; blue coloration commonly reflects trace impurities or inclusions. Calcite occurs from ancient to modern geological settings.

Uses & applications

Used in cement, lime, aggregate, and industrial calcium products; attractive blue clusters are sold as decorative and collector specimens. It is generally too soft for durable jewelry.

Geological facts

Calcite effervesces vigorously in dilute hydrochloric acid and commonly shows strong birefringence, producing doubled images through clear pieces. Blue calcite is often confused with celestite or blue fluorite.

Field identification & locations

Identify by its softness, rhombohedral cleavage, and acid reaction; common localities include Mexico, Morocco, the United States, and China. Avoid vinegar unless necessary, as weak acids may react slowly and damage surfaces.