mineral
Massive calcite (likely limestone-derived calcite)
Calcite, calcium carbonate (CaCO₃); possibly a chalky limestone fragment
AI-generated identification · may be incorrectWhite to cream, opaque, earthy to vitreous luster, irregular granular texture, and no obvious crystal faces. Calcite has Mohs hardness 3, perfect rhombohedral cleavage, specific gravity about 2.71, and effervesces strongly with dilute hydrochloric acid or vinegar (more slowly).
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Physical properties
White to cream, opaque, earthy to vitreous luster, irregular granular texture, and no obvious crystal faces. Calcite has Mohs hardness 3, perfect rhombohedral cleavage, specific gravity about 2.71, and effervesces strongly with dilute hydrochloric acid or vinegar (more slowly).
Formation & geological history
Forms by precipitation from carbonate-rich water, biological accumulation, or alteration of limestone; specimens may range from recent deposits to Paleozoic–Mesozoic sedimentary rocks. The image alone cannot establish its exact age or whether it is pure calcite versus limestone.
Uses & applications
Used in cement, lime, aggregate, soil treatment, glass manufacture, and industrial fillers; clear crystals are collected, but this rough piece has little jewelry value.
Geological facts
Calcite is one of the most abundant carbonate minerals and commonly occurs as rhombohedra, scalenohedra, or massive chalky material. Double refraction is visible through clear calcite crystals.
Field identification & locations
Likely from a limestone, marble, cave, or carbonate vein. Confirm with acid fizz, a scratch test against a copper coin or steel nail, and inspection for rhombohedral cleavage; dolomite reacts weakly unless powdered.
