mineral

Calcite crystal cluster

Calcite (calcium carbonate, CaCO₃), likely on a carbonate matrix

AI-generated identification · may be incorrect

Cream to translucent-white, vitreous to pearly luster, prominent rhombohedral cleavage, Mohs hardness 3, and specific gravity about 2.71. The bladed/scalenohedral crystal forms and stepped cleavage surfaces are characteristic, though the image does not permit a definitive test.

Identified August 24, 2026More mineral →

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Physical properties

Formation & geological history

Likely precipitated from carbonate-rich groundwater or hydrothermal fluids in a cavity or vein; the underlying material may be limestone or another carbonate rock. Calcite is geologically widespread and forms from Precambrian to modern ages.

Uses & applications

Used in cement, lime, aggregate, glass, soil treatment, and chemical manufacture; clear crystals are collectible but generally not jewelry stones because of softness and cleavage.

Geological facts

Calcite effervesces strongly with dilute hydrochloric acid or vinegar, though vinegar may react slowly. It commonly shows double refraction and can fluoresce under ultraviolet light.

Field identification & locations

The specimen is visually consistent with calcite, but aragonite or gypsum are possible alternatives. Around 48.9°N, 2.4°E (Paris region), carbonate rocks and construction-derived material are plausible; test hardness and acid reaction before assigning locality.