gemstone

Tumbled amethyst

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

AI-generated identification · may be incorrect

Mohs hardness 7; translucent to opaque deep violet-purple, vitreous luster, typically lacking visible crystal faces because it is polished. Quartz has a trigonal crystal structure, no cleavage, and conchoidal fracture; specific gravity is about 2.65.

Identified September 17, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich fluids fill cavities in volcanic rocks, especially basalt, where quartz crystals grow over long periods, commonly during the Mesozoic to Cenozoic eras. This specimen has been rounded and polished by human processing.

Uses & applications

Used for inexpensive jewelry, ornaments, carvings, metaphysical objects, and mineral collecting; high-quality crystal clusters and faceted stones have greater gem value.

Geological facts

Amethyst’s purple color can fade with prolonged heat or strong sunlight. It is the birthstone for February and is the purple variety of quartz.

Field identification & locations

Identify it by its purple color, glassy luster, hardness, and resistance to scratching by steel; it should not scratch glass easily if heavily coated, but genuine quartz will. Common sources include Brazil, Uruguay, Zambia, and Mexico.