mineral

Uncertain translucent mineral specimen, possibly calcite

Calcite (calcium carbonate, CaCO₃), tentative identification

AI-generated identification · may be incorrect

Gray-brown translucent crystals with a vitreous to pearly luster and prominent cleavage; calcite has Mohs hardness 3, trigonal crystal structure, and specific gravity about 2.71. The image alone cannot exclude gypsum, aragonite, or another cleavable mineral.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed by precipitation from hydrothermal fluids or groundwater in a cavity, vein, or sedimentary setting; age cannot be determined from the photograph. Calcite occurs in limestones, veins, geodes, and caves worldwide.

Uses & applications

Calcite is used in cement, lime, aggregate, optical instruments, and as a collector mineral; transparent varieties may be decorative but are generally not jewelry durable.

Geological facts

A vinegar or dilute hydrochloric-acid test should produce effervescence if it is calcite, though coatings or impurities may reduce the reaction. Cleavage fragments commonly form rhombohedral shapes rather than sharp conchoidal fractures.

Field identification & locations

Common localities include Mexico, Iceland, the United States, China, and many limestone regions. Confirm with hardness, acid reaction, cleavage, and ideally specific-gravity or Raman testing.