gemstone

Polished purple gemstone, likely amethyst

Amethyst: purple quartz, silicon dioxide (SiO₂)

AI-generated identification · may be incorrect

Hardness 7 Mohs; vitreous luster, purple coloration from iron and irradiation, and hexagonal quartz structure. The rounded, polished form obscures natural cleavage; quartz has no cleavage and conchoidal fracture.

Identified August 25, 2026More gemstone →

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Physical properties

Formation & geological history

Amethyst forms when quartz crystallizes in volcanic cavities, with iron impurities later irradiated by natural radioactivity; many deposits are Mesozoic to younger. The pictured piece appears cut and polished rather than naturally crystal-faced.

Uses & applications

Used in jewelry, carvings, ornaments, and mineral collections. Common polished pieces typically have modest value unless color, clarity, and provenance are exceptional.

Geological facts

Purple intensity varies with iron content and heat treatment; heating can produce yellow citrine-like colors. Amethyst is February’s birthstone.

Field identification & locations

Identify by its purple color, glassy luster, hardness, and lack of cleavage; test cautiously because glass and synthetic materials can look similar. Important sources include Brazil, Uruguay, Zambia, and Mexico.