mineral

Milky calcite

Calcite (CaCO₃), likely a cleavage fragment

AI-generated identification · may be incorrect

White to translucent, vitreous-to-pearly luster, prominent rhombohedral cleavage, and hardness Mohs 3; commonly shows curved or stepped cleavage surfaces and moderate density (specific gravity ~2.71).

Identified August 29, 2026More mineral →

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Physical properties

Formation & geological history

Forms when calcium carbonate precipitates from groundwater or hydrothermal fluids, and in limestone, marble, and cave deposits; the specimen’s precise geological age cannot be determined from the image.

Uses & applications

Used in cement, lime, aggregate, glass manufacture, agriculture, and chemical processing; clear optical calcite is collectible, while ordinary pieces have little commercial value.

Geological facts

Calcite effervesces visibly in dilute hydrochloric acid or strong vinegar, unlike quartz; transparent Iceland spar can display double refraction.

Field identification & locations

The blocky translucent appearance and excellent cleavage favor calcite over quartz, which lacks cleavage and is harder. Common worldwide, especially in limestone regions, hydrothermal veins, and caves.