mineral

Raw calcite

Calcite (CaCO₃), likely massive or crystalline aggregate

AI-generated identification · may be incorrect

Typically Mohs hardness 3, white to pale honey-green, with a vitreous to pearly luster and prominent rhombohedral cleavage; translucent fragments and sparkling cleavage surfaces are characteristic. Exact identification should be confirmed by an acid-fizz test and hardness testing.

Identified August 16, 2026More mineral →

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Physical properties

Formation & geological history

Calcite commonly precipitates from groundwater, hydrothermal fluids, and marine sediments, forming veins, cavities, limestones, and cave deposits over many geological ages. The specimen appears to be a natural, unpolished aggregate rather than a distinct crystal.

Uses & applications

Used extensively to manufacture cement and lime, as a soil neutralizer, and as a source of calcium carbonate; transparent crystals are collected and occasionally used decoratively. This rough piece has modest specimen value.

Geological facts

Calcite is strongly birefringent: clear pieces can show double refraction. It effervesces visibly in dilute hydrochloric acid or vinegar, though vinegar may react slowly.

Field identification & locations

Common worldwide, especially in limestone regions, hydrothermal veins, and caves; major localities include Mexico, Iceland, the United States, and China. Distinguish it from quartz by its softness, cleavage, and acid reaction.