mineral
Clear calcite cleavage fragment
Calcite (calcium carbonate, CaCO₃)
AI-generated identification · may be incorrectColorless to translucent, with vitreous-to-pearly luster and prominent rhombohedral cleavage; Mohs hardness 3, typically white streak, and specific gravity about 2.71. The block-like shape and stepped cleavage surfaces are consistent with calcite, though image quality limits certainty.
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Physical properties
Colorless to translucent, with vitreous-to-pearly luster and prominent rhombohedral cleavage; Mohs hardness 3, typically white streak, and specific gravity about 2.71. The block-like shape and stepped cleavage surfaces are consistent with calcite, though image quality limits certainty.
Formation & geological history
Forms in limestone, marble, hydrothermal veins, caves, and evaporite environments by precipitation or recrystallization; specimens may range from ancient to modern depending on locality. It is not an igneous, sedimentary, or metamorphic rock itself, but a mineral commonly composing those rocks.
Uses & applications
Used industrially for cement, lime, aggregate, soil treatment, and chemical manufacture; transparent specimens are collected and occasionally used decoratively. It is generally unsuitable for jewelry because of its softness and perfect cleavage.
Geological facts
Calcite effervesces readily with dilute hydrochloric acid or strong vinegar, especially on a fresh surface, and commonly exhibits double refraction. Its cleavage angles produce distinctive rhombohedra rather than true cubes.
Field identification & locations
Identify by testing hardness against a copper coin or steel knife, observing rhombohedral cleavage, and performing an acid test; common localities include Mexico, Iceland, the United States, and China. Avoid scratching or impact because it is soft and brittle.
