gemstone

Tumbled amethyst quartz

Quartz (SiO₂), purple variety amethyst

AI-generated identification · may be incorrect

Mohs hardness 7; translucent pale lavender to purple, with vitreous luster and no cleavage. Trigonal crystal structure; specific gravity about 2.65, though the rounded polished form obscures crystal faces.

Identified September 21, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when iron-bearing quartz crystallizes in gas cavities of volcanic rocks, especially basalt, and irradiation produces the purple color. Most gem amethyst formed in hydrothermal or volcanic settings during the Mesozoic and younger geologic eras.

Uses & applications

Used for inexpensive jewelry, carvings, ornaments, and mineral collections. Small tumbled pieces commonly have modest decorative value.

Geological facts

Purple color results mainly from iron impurities and irradiation; heating can turn some amethyst yellow, producing citrine. Very pale material may be sold as “Rose de France” amethyst.

Field identification & locations

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