mineral

Calcite specimen

Calcite (calcium carbonate, CaCO₃), likely pale blue-green massive or cleaved calcite with iron-oxide staining

AI-generated identification · may be incorrect

Typically Mohs hardness 3, pearly to vitreous luster, white to pale blue-green color, and excellent rhombohedral cleavage; transparent to translucent crystals commonly show curved or stepped cleavage surfaces. Effervesces strongly in dilute hydrochloric acid or vinegar, though vinegar reacts slowly.

Identified September 10, 2026More mineral →

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Physical properties

Formation & geological history

Forms in limestone, hydrothermal veins, cavities, and sedimentary deposits through precipitation from carbonate-rich fluids. Calcite occurs from ancient to modern geological settings; the orange-brown material may be iron-oxide staining or attached matrix.

Uses & applications

Used in cement, lime, aggregate, optical instruments, and as a carbonate mineral specimen; attractive transparent crystals are collected, while blue calcite is sometimes used decoratively.

Geological facts

Calcite is one of Earth’s most abundant minerals and has strong birefringence, producing double images through clear pieces. Color alone is not diagnostic because impurities create many varieties.

Field identification & locations

Look for rhombohedral cleavage, softness, and acid fizz; distinguish it from quartz, which is harder and lacks cleavage. Common worldwide, especially in limestone regions, hydrothermal veins, and caves.