mineral
Calcite fragment
Calcite (calcium carbonate, CaCO₃), possibly weathered limestone
AI-generated identification · may be incorrectPale 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.
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Physical properties
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.
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.
