mineral

Blue calcite (likely, with possible aragonite)

Calcite, CaCO₃

AI-generated identification · may be incorrect

Pale blue, translucent, vitreous to pearly luster; Mohs hardness 3, perfect rhombohedral cleavage, trigonal crystal structure, and specific gravity about 2.71. The pieces appear polished or naturally cleavage-fragmented.

Identified September 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms in sedimentary carbonate deposits, hydrothermal veins, and cavities; blue color commonly results from inclusions or trace elements. Most specimens are geologically young relative to Earth history, commonly formed during Phanerozoic mineralization.

Uses & applications

Used mainly as a collector mineral, ornamental stone, and occasionally for carvings; calcite is also important industrially in cement, lime, aggregate, and fillers.

Geological facts

Calcite effervesces strongly with dilute hydrochloric acid and shows birefringence when viewed through clear pieces. Blue calcite is commonly confused with blue aragonite, celestite, or dyed material.

Field identification & locations

Common sources include Mexico, Madagascar, Brazil, and the United States. Test a hidden edge for acid reaction and cleavage; avoid scratching polished surfaces, since calcite is soft.