mineral

Calcite fragment

Calcite (calcium carbonate, CaCO₃), possibly weathered limestone

AI-generated identification · may be incorrect

Pale cream to honey-colored, translucent, with a vitreous to pearly luster and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. The orange-brown line may be iron-oxide staining or a natural vein.

Identified September 3, 2026More mineral →

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Physical properties

Formation & geological history

Calcite commonly precipitates from groundwater, forms in limestone and hydrothermal veins, or crystallizes in cavities; the specimen’s exact age and setting cannot be determined from the image. Limestone deposits range from Precambrian to modern.

Uses & applications

Used to manufacture cement, lime, aggregate, and agricultural soil amendments; clear optical calcite is collectible, while ordinary fragments have minimal commercial value.

Geological facts

Calcite effervesces strongly in dilute hydrochloric acid or vinegar, though vinegar reacts more slowly; it can show double refraction in clear pieces.

Field identification & locations

Identify by its softness, rhombohedral cleavage, and acid reaction; common worldwide in limestone, marble, caves, and veins. Avoid confusing it with harder quartz or feldspar.