mineral

Blue calcite (probable)

Calcite, calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

Pale blue to blue-gray, cloudy and massive, with a vitreous-to-pearly luster; calcite has Mohs hardness 3, perfect rhombohedral cleavage, and specific gravity about 2.71. The rounded, irregular piece appears rough or naturally broken rather than crystalline.

Identified September 13, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed by hydrothermal or sedimentary precipitation of calcite, with trace elements causing the blue color; its exact geological age cannot be determined from the photograph. Common sources include Mexico, Madagascar, Pakistan, and parts of the United States.

Uses & applications

Used mainly as a collector specimen, ornamental stone, and occasionally for decorative carving; calcite is also important industrially in cement, lime, aggregate, and chemical manufacture.

Geological facts

Blue calcite is commonly confused with blue aragonite, celestine, or dyed materials. A drop of dilute hydrochloric acid or vinegar should produce visible effervescence, though testing can damage the specimen.

Field identification & locations

Identify by its softness, rhombohedral cleavage, and acid reaction; a copper coin or steel knife may scratch it. The specimen’s blue color and massive texture support blue calcite, but laboratory testing would be needed for certainty.