mineral

Amethyst tumbled stones

Quartz, SiO₂; purple coloration from irradiation and trace iron

AI-generated identification · may be incorrect

Mohs hardness 7; purple to violet, vitreous luster, trigonal crystal structure, and poor or indistinct cleavage. The specimens appear polished/tumbled, with one showing bluish inclusions or surface coating; exact identification is image-limited.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Forms when iron-bearing quartz crystallizes in gas cavities and fractures of volcanic rocks, especially basalt, as silica-rich groundwater circulates. Major deposits occur in Brazil, Uruguay, Zambia, and Namibia; ages vary from Mesozoic to younger hydrothermal systems.

Uses & applications

Used as ornamental stone, jewelry, carvings, crystal specimens, and abrasives; high-quality transparent material is faceted as a gemstone.

Geological facts

Amethyst is the purple variety of quartz and can fade with prolonged heat or strong sunlight. Heat treatment commonly converts it to yellow citrine or produces mixed ametrine-like colors.

Field identification & locations

Identify by purple color, glassy luster, hardness sufficient to scratch ordinary glass, and lack of cubic cleavage; quartz has a white streak. Common localities include Brazilian and Uruguayan basalt geodes, often with druzy quartz and agate.