mineral

Rough blue calcite

Calcite (CaCO₃), likely blue calcite

AI-generated identification · may be incorrect

Typically pale sky-blue to gray-blue, translucent to opaque, with a vitreous to pearly luster and prominent rhombohedral cleavage; Mohs hardness 3 and specific gravity about 2.71. The specimen’s pale color and chalky-looking broken surfaces fit calcite, though image-only identification is not definitive.

Identified September 1, 2026More mineral →

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Physical properties

Formation & geological history

Calcite forms in hydrothermal veins, sedimentary limestones, caves, and metamorphic marbles; blue coloration commonly results from trace inclusions or structural defects. Individual specimens may range from recent deposits to Precambrian host rocks.

Uses & applications

Used industrially for cement, lime, aggregate, agriculture, and chemical manufacture; attractive blue crystals are sold as inexpensive decorative or metaphysical specimens.

Geological facts

Calcite effervesces strongly with dilute hydrochloric acid or vinegar when freshly powdered or scratched. It shows excellent rhombohedral cleavage and strong birefringence, producing doubled images through clear pieces.

Field identification & locations

Look for easy scratching with a copper coin or steel knife, rhombohedral cleavage, and acid fizz; distinguish it from blue fluorite, which is harder and commonly cubic. Common sources include Mexico, Morocco, Brazil, and the United States.