mineral

Blue calcite (likely)

Calcite, calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

Pale blue, translucent-to-opaque, with a matte-to-vitreous luster; Mohs hardness 3, perfect rhombohedral cleavage, trigonal crystal structure, and specific gravity about 2.71. The rounded, polished form obscures cleavage and crystal faces.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Blue calcite forms mainly in hydrothermal veins and carbonate-rich sedimentary environments, commonly as a secondary mineral in limestone or marble. Its age depends on the deposit, ranging from ancient to recent geological periods.

Uses & applications

Used primarily as a decorative, lapidary, and metaphysical specimen; calcite is also important industrially in cement, lime, aggregate, and calcium-carbonate products.

Geological facts

It reacts vigorously with dilute hydrochloric acid, producing effervescence; blue color may result from trace impurities or structural defects. It can scratch with a steel knife but is easily scratched by quartz.

Field identification & locations

Common sources include Mexico, Madagascar, Brazil, and the United States. Distinguish it from blue chalcedony or fluorite by its softness, rhombohedral cleavage, and acid reaction.