mineral

Amethyst geode

Quartz (SiO₂), purple variety amethyst; typically hosted in volcanic basalt

AI-generated identification · may be incorrect

Hardness 7 Mohs; vitreous luster; purple quartz crystals lining a hollow cavity, with conchoidal fracture and no cleavage. Color comes mainly from iron impurities and irradiation; geode rims may include chalcedony or agate.

Identified August 27, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater filled vesicles in basaltic lava, depositing quartz crystals over time; commonly Cretaceous to Cenozoic in age, depending on locality. The pictured specimen is cut and polished at its base and rim.

Uses & applications

Used for mineral collecting, décor, and jewelry; large geodes are popular display pieces. Amethyst is also the February birthstone, though “healing” claims lack scientific support.

Geological facts

Brazil and Uruguay produce major geodes; Uruguayan material is often intensely saturated purple with dark interiors. Heating amethyst can produce citrine-like yellow-orange quartz.

Field identification & locations

Identify by purple, glassy, six-sided quartz crystals lining a cavity, hardness near 7, and lack of cleavage; distinguish dyed quartz by uneven color concentration or dye in fractures. Common sources include Brazil, Uruguay, Mexico, and Zambia.