mineral

Amethyst geode

Quartz (SiO₂), purple variety amethyst; commonly in basalt-hosted geodes

AI-generated identification · may be incorrect

Violet, translucent quartz crystals line a hollow cavity, with a pale gray-white chalcedony/quartz rind. Mohs hardness 7; vitreous luster; trigonal crystal structure; no cleavage, conchoidal fracture; specific gravity about 2.65.

Identified August 10, 2026More mineral →

Explore Amethyst geode in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Silica-rich groundwater filled gas cavities in volcanic basalt, depositing chalcedony and later amethyst crystals over long periods, generally in Mesozoic to Cenozoic volcanic terrains. The specimen is likely from Brazil or Uruguay, major commercial sources.

Uses & applications

Used for mineral collecting, décor, bookends, and cabochons or faceted jewelry; large geodes are popular display pieces. It has limited industrial value compared with ordinary quartz.

Geological facts

Purple color results mainly from iron impurities and irradiation. Deeper, saturated violet crystals—especially from Uruguay—are generally more valuable than pale Brazilian material.

Field identification & locations

Identify it by the hollow cavity, radiating quartz points, purple color, glassy luster, and hardness sufficient to scratch glass; avoid confusing it with purple glass or fluorite. Common localities include Brazil, Uruguay, Mexico, and Zambia.