mineral

Tumbled amethyst

Quartz, SiO₂; purple variety colored mainly by iron-related defects

AI-generated identification · may be incorrect

Mohs hardness 7; translucent purple with white/colorless zones, vitreous luster, and conchoidal fracture. Hexagonal crystal structure, though tumbling has removed crystal faces; apparent specific gravity is about 2.65.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich hydrothermal fluids fill cavities in volcanic rocks, especially basalt, where iron-bearing quartz develops its purple color through irradiation and heating. Most commercial material is Cretaceous to younger, commonly from Brazil and Uruguay.

Uses & applications

Used as a gemstone, decorative tumbled stone, jewelry, carvings, and collector specimens. It is attractive but generally common and moderately priced.

Geological facts

Amethyst is the February birthstone and was historically valued as a protective stone. Heating can turn some material yellow-orange, producing citrine.

Field identification & locations

Identify it by purple quartz hardness, glassy luster, lack of cleavage, and inability to scratch it with a steel knife; glass may resemble it but is softer or similar in hardness. Common sources include Brazil, Uruguay, Zambia, and Bolivia.