mineral

Calcite

Calcite (calcium carbonate, CaCO₃), likely a massive crystalline specimen

AI-generated identification · may be incorrect

Typically colorless to white, translucent, with vitreous to pearly luster and prominent rhombohedral cleavage; Mohs hardness 3 and specific gravity about 2.71. The blocky, stepped cleavage surfaces visible here strongly support calcite, though aragonite or quartz are less likely.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms in sedimentary limestones, hydrothermal veins, caves, and cavities in igneous rocks through precipitation from calcium-rich fluids. Individual specimens may range from recent cave deposits to Paleozoic or older host-rock formations.

Uses & applications

Used extensively to manufacture cement, lime, aggregate, and agricultural soil amendments; transparent optical calcite is collectible. This rough specimen generally has modest decorative and educational value.

Geological facts

Calcite effervesces vigorously with cold dilute hydrochloric acid and may fluoresce under ultraviolet light. Its cleavage fragments are rhombohedral rather than cubic.

Field identification & locations

Common worldwide, including Mexico, the United States, Iceland, Brazil, and China; identify by softness, rhombohedral cleavage, and acid reaction. A steel knife can scratch it, while it should not scratch glass.