mineral

Amethyst geode

Amethyst (purple quartz), SiO₂; crystalline quartz lining a geode

AI-generated identification · may be incorrect

Purple, vitreous luster, typically Mohs 7; trigonal quartz crystals grow inward from a cavity, with no true cleavage. The outer rind is not clearly visible in this image.

Identified September 25, 2026More mineral →

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Physical properties

Purple, vitreous luster, typically Mohs 7; trigonal quartz crystals grow inward from a cavity, with no true cleavage. The outer rind is not clearly visible in this image.

Formation & geological history

Silica-rich fluids deposited quartz in a gas bubble or cavity in volcanic rock; iron impurities and natural irradiation produced the purple color. Geode ages vary widely, commonly millions to hundreds of millions of years.

Uses & applications

Used for display, collecting, jewelry, and decorative objects; amethyst is also cut into cabochons and facets.

Geological facts

Amethyst is the purple variety of quartz; heating can alter its color, sometimes producing yellow-orange citrine-like material.

Field identification & locations

Identify by the inward-pointing purple quartz crystals and glassy luster; major sources include Brazil, Uruguay, and Zambia. The pictured specimen appears cut or polished around its edge.