mineral

Amethyst geode/druse

Quartz, SiO₂; purple variety amethyst

AI-generated identification · may be incorrect

Violet, translucent quartz crystals lining cavities in gray-brown host rock; vitreous luster, hexagonal crystal structure, Mohs hardness 7, no cleavage, conchoidal fracture, and specific gravity about 2.65.

Identified August 9, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals inside gas cavities or fractures in volcanic basalt, commonly during the Jurassic–Cretaceous eras. The purple color results mainly from iron impurities and natural irradiation.

Uses & applications

Used for mineral collecting, ornamentation, cabochons, carvings, and jewelry; larger geodes are decorative display pieces. Common specimens typically sell for $10–$75, while exceptionally large or vividly colored pieces may exceed $200.

Geological facts

The left specimen is an amethyst druse with exposed crystal points; the right appears to be a cut or broken geode section with a crystalline cavity. Amethyst is the official birthstone for February.

Field identification & locations

Identify it by purple hexagonal quartz crystals that scratch glass but are not scratched by a steel knife; avoid confusing it with purple glass or fluorite, which is softer. Major sources include Brazil, Uruguay, Zambia, Mexico, and the United States.