gemstone

Polished amethyst cabochon

Amethyst, purple quartz (SiO₂)

AI-generated identification · may be incorrect

Mohs hardness 7; vitreous luster; purple coloration from iron and irradiation, often with zoning or banding. Quartz has a trigonal crystal structure and no true cleavage, with conchoidal fracture; the pictured stone is polished and set in jewelry.

Identified September 16, 2026More gemstone →

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Physical properties

Formation & geological history

Forms mainly in silica-rich volcanic geodes and hydrothermal veins when iron-bearing quartz develops purple color through natural irradiation. Most gem amethyst comes from relatively young volcanic provinces, especially Brazil, Uruguay, Zambia, and Bolivia.

Uses & applications

Used for cabochons, faceted jewelry, ornamental objects, and mineral collections. It is durable for rings but can scratch or chip with heavy wear.

Geological facts

Amethyst is the February birthstone and the purple variety of quartz; heating commonly turns it yellow-orange, producing citrine. Its color may fade with prolonged strong sunlight or heat.

Field identification & locations

Identify it by purple quartz color, glassy luster, hardness, and conchoidal fracture; banding and translucent areas support identification, though dyes and synthetic quartz can imitate it. Common localities include Brazil, Uruguay, Zambia, and Arizona.