gemstone

Tumbled amethyst

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

AI-generated identification · may be incorrect

Mohs hardness 7; translucent to opaque violet-purple, vitreous luster, trigonal crystal structure, no cleavage, conchoidal fracture, specific gravity about 2.65. The smooth shape indicates tumbling and polishing.

Identified August 9, 2026More gemstone →

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Physical properties

Formation & geological history

Forms chiefly in cavities of volcanic rocks, especially basalt, where silica-rich fluids deposit quartz crystals; major deposits are geologically young to Paleozoic in Brazil, Uruguay, Zambia, and elsewhere.

Uses & applications

Used for inexpensive cabochons, beads, ornaments, carvings, and mineral specimens; high-quality transparent crystals are used in jewelry, while most commercial pieces have modest value.

Geological facts

Amethyst is the purple variety of quartz and is February’s birthstone. Heating can turn it yellow-orange, producing citrine or ametrine-like material.

Field identification & locations

Identify by its purple color, glassy luster, hardness, and lack of cleavage; quartz will scratch glass but not be scratched by a steel knife. Natural color zoning and irregular inclusions help distinguish it from glass or synthetic material.