gemstone

Tumbled amethyst

Amethyst, purple quartz (SiO₂), colored primarily by iron impurities and irradiation

AI-generated identification · may be incorrect

Mohs hardness 7; transparent to translucent purple, with vitreous luster and conchoidal fracture. Quartz is trigonal and lacks cleavage; the rounded surface is human-tumbled and polished.

Identified August 31, 2026More gemstone →

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Physical properties

Mohs hardness 7; transparent to translucent purple, with vitreous luster and conchoidal fracture. Quartz is trigonal and lacks cleavage; the rounded surface is human-tumbled and polished.

Formation & geological history

Forms mainly in cavities of volcanic rocks when silica-rich groundwater deposits quartz crystals, commonly during late stages of basalt formation. Most specimens are Phanerozoic, though host-rock ages vary widely.

Uses & applications

Used in jewelry, ornamental carvings, polished stones, and mineral collections. Fine saturated purple material can be valuable, while ordinary tumbled pieces are inexpensive.

Geological facts

Purple color ranges from lilac to deep violet and may fade with prolonged sunlight or heating. Amethyst is the February birthstone and a variety of macrocrystalline quartz.

Field identification & locations

Identify it by its glassy luster, hardness, quartz-like fracture, and purple color; it should scratch glass but not be scratched by a steel knife. Major sources include Brazil, Uruguay, Zambia, Bolivia, and Mexico.