mineral

Amethyst cluster

Amethyst, purple quartz (SiO₂)

AI-generated identification · may be incorrect

Mohs hardness 7; purple, vitreous luster, typically hexagonal quartz crystals with indistinct cleavage and conchoidal fracture; specific gravity about 2.65. The specimen appears to be a natural crystal cluster or crystal-lined fragment, possibly with darker matrix attached.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when iron-bearing quartz in volcanic cavities is exposed to mildly radioactive or oxidizing fluids, commonly in basalt geodes. Many commercial specimens formed in Mesozoic–Cenozoic volcanic regions, especially Brazil and Uruguay.

Uses & applications

Used as a gemstone, ornamental display stone, carved object, and popular collecting specimen; fine transparent crystals are faceted, while clusters are decorative.

Geological facts

Purple color results mainly from irradiation-related defects involving iron impurities. Heating can turn amethyst yellow or orange, producing citrine-like material.

Field identification & locations

Identify by purple quartz crystals, glassy luster, hardness sufficient to scratch ordinary glass, and lack of obvious cubic cleavage. Common sources include Brazil, Uruguay, Zambia, Namibia, and Mexico.