gemstone

Tumbled amethyst

Amethyst, purple quartz (SiO₂)

AI-generated identification · may be incorrect

Mohs hardness 7; transparent to translucent purple color from trace iron and irradiation, with vitreous luster and no cleavage. It has a trigonal crystal structure, though tumbling rounds its natural edges; visible fractures and color zoning are common.

Identified September 3, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when iron-bearing quartz crystallizes in cavities of volcanic rocks, especially basaltic geodes, often alongside agate and calcite. The host rocks range from Paleozoic to Cenozoic in age, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, jewelry, décor, and mineral collecting; fine transparent purple material has greater gem value.

Geological facts

Heating can turn amethyst yellow-orange, producing citrine, while excessive heat may cause cracking or color loss. Purple coloration is commonly strongest near crystal tips or cavity walls.

Field identification & locations

Identify by its purple quartz appearance, glassy luster, hardness, and lack of cleavage; it should scratch ordinary glass but not be scratched by a steel blade. Major sources include Brazil, Uruguay, Zambia, and Bolivia.