metamorphic
Calcite-rich limestone or marble fragment
Calcite (CaCO₃), likely recrystallized carbonate rock
AI-generated identification · may be incorrectCreamy white, translucent-to-opaque, with pearly to vitreous luster and irregular cleavage surfaces; calcite has Mohs hardness 3, rhombohedral cleavage, and specific gravity about 2.71. The rounded, layered appearance may indicate a fossiliferous limestone or carbonate concretion rather than true marble.
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Physical properties
Creamy white, translucent-to-opaque, with pearly to vitreous luster and irregular cleavage surfaces; calcite has Mohs hardness 3, rhombohedral cleavage, and specific gravity about 2.71. The rounded, layered appearance may indicate a fossiliferous limestone or carbonate concretion rather than true marble.
Formation & geological history
Formed from accumulated marine carbonate sediments later lithified; if recrystallized, it became marble during low- to medium-grade metamorphism. Carbonate rocks commonly range from Paleozoic to Cenozoic in age.
Uses & applications
Used for cement, agricultural lime, aggregate, dimension stone, and decorative carving; attractive polished pieces may be sold as specimen material. This small fragment has little commercial value.
Geological facts
Calcite effervesces strongly with dilute hydrochloric acid or vinegar, though vinegar reacts more slowly. Its three-direction rhombohedral cleavage distinguishes it from quartz, which is much harder and lacks cleavage.
Field identification & locations
Common in limestone, marble, caves, hydrothermal veins, and fossil beds worldwide; major sources include Italy, Mexico, the United States, and the United Kingdom. Test a fresh surface with vinegar and try scratching it with a steel knife (calcite scratches readily).
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