mineral

Tumbled amethyst

Quartz, purple variety; silicon dioxide (SiO₂), colored mainly by iron impurities and irradiation

AI-generated identification · may be incorrect

Mohs hardness 7; vitreous luster; purple to violet with translucent areas and possible brown host-rock inclusions. Crystalline quartz has a trigonal structure and no cleavage, with conchoidal fracture; polishing obscures natural faces.

Identified August 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms in cavities of volcanic rocks, especially basaltic geodes, when silica-rich groundwater deposits quartz and trace iron; coloration develops through irradiation and heat. Most specimens formed in Phanerozoic volcanic environments, commonly tens to hundreds of millions of years old.

Uses & applications

Used as an ornamental and jewelry gemstone, in carvings, beads, and geode specimens; tumbled pieces are usually inexpensive collectibles.

Geological facts

The purple color can fade with prolonged strong sunlight or heating. Amethyst is the birthstone for February and is the purple variety of quartz.

Field identification & locations

Identify by its glassy luster, hardness, quartz-like density (about 2.65), and purple color; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, Zambia, and Namibia.