gemstone

Amethyst crystal point

Amethyst, purple quartz (SiO₂)

AI-generated identification · may be incorrect

Mohs hardness 7; typically violet to purple with a vitreous luster and hexagonal crystal structure. The specimen appears polished or tumbled, with a pale quartz-like termination and dark purple translucent body; cleavage is absent, with conchoidal fracture.

Identified August 31, 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, with purple color produced by irradiation and iron impurities. Most deposits are Cenozoic to Mesozoic in age, depending on locality.

Uses & applications

Used for jewelry, carvings, ornamental objects, and mineral collecting. Common polished pieces generally have modest commercial value.

Geological facts

Amethyst is the purple variety of quartz and is February’s birthstone. Prolonged heating or sunlight exposure can fade its color or transform it toward yellow citrine tones.

Field identification & locations

Identify it by purple color, glassy luster, hardness sufficient to scratch ordinary glass, and lack of cleavage; natural crystals often show pointed hexagonal faces or banding. Major sources include Brazil, Uruguay, Zambia, and Namibia.