mineral

Blue calcite

Calcite, CaCO₃

AI-generated identification · may be incorrect

Pale blue-gray, translucent to cloudy, with a vitreous to pearly luster and prominent rhombohedral cleavage; Mohs hardness 3, trigonal crystal system, specific gravity about 2.7. The specimen’s appearance is consistent with rough calcite, though a photo cannot confirm the identification.

Identified September 25, 2026More mineral →

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Physical properties

Formation & geological history

Calcite commonly forms when calcium-rich fluids precipitate in sedimentary rocks, veins, and cavities; it occurs across a wide range of geological ages. Blue color is generally caused by trace impurities or structural defects.

Uses & applications

Used as a decorative and collectible mineral; calcite is also an important industrial source of lime and a component of cement and building stone.

Geological facts

Calcite effervesces in dilute acid and is softer than a steel knife. It can show strong double refraction in transparent crystals.

Field identification & locations

Look for rhombohedral cleavage and scratchability; blue calcite is found in several localities worldwide, including Mexico and Madagascar. Avoid acids when testing a collectible specimen.