mineral

Calcite crystal specimen

Calcite (calcium carbonate, CaCO₃)

AI-generated identification · may be incorrect

Typically pale honey-yellow to cream, translucent, with a vitreous to pearly luster and rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. The porous, irregular form may be crystalline calcite coating or replacing a cavity-bearing host rock.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms in limestone caves, hydrothermal veins, sedimentary cavities, and mineral-rich groundwater deposits, commonly from the Paleozoic to Recent. The image alone cannot establish its precise age or locality.

Uses & applications

Used to manufacture cement, lime, glass, and agricultural soil additives; attractive crystals are collected, though this rough specimen has limited gem value.

Geological facts

Calcite effervesces vigorously with dilute hydrochloric acid or household vinegar, though vinegar may react slowly. It commonly shows strong birefringence, making printed text appear doubled through clear fragments.

Field identification & locations

Look for rhombohedral cleavage, softness, and acid fizz; distinguish it from quartz, which is harder and does not react with acid. Common worldwide, especially in limestone regions, Mexico, the United States, Iceland, and China.