mineral

Calcite crystal cluster (dogtooth/saddle calcite)

Calcite — calcium carbonate, CaCO₃

AI-generated identification · may be incorrect

Typically white to gray, vitreous to pearly, with abundant sharp scalenohedral (“dogtooth”) crystals; Mohs hardness 3, perfect rhombohedral cleavage, trigonal crystal structure, and specific gravity about 2.71. The blue-gray coloration may result from inclusions or surface treatment.

Identified August 7, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in hydrothermal veins, limestone cavities, and geodes when calcium-rich fluids precipitate carbonate minerals. Individual crystals can form over relatively short geological intervals, commonly from Paleozoic to Cenozoic host rocks.

Uses & applications

Used for ornamental mineral specimens, acid-neutralizing materials, cement, lime, glass manufacture, and aggregate; attractive crystals are collected rather than used as gemstones.

Geological facts

Calcite effervesces vigorously in dilute hydrochloric acid and shows strong birefringence, producing doubled images through clear fragments. The specimen’s radiating, pointed crystals are characteristic of dogtooth calcite.

Field identification & locations

Identify by its low hardness, rhombohedral cleavage, acid reaction, and crystal points; common localities include the United States, Mexico, China, Morocco, and England. Handle carefully because the crystals are brittle and easily cleaved.