mineral

Amethyst geode slices

Amethyst, purple quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness 7 Mohs; purple, vitreous luster, hexagonal quartz crystals lining cavities, commonly with white quartz and gray chalcedony or basalt matrix. No cleavage; specific gravity about 2.65.

Identified August 8, 2026More mineral →

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Physical properties

Hardness 7 Mohs; purple, vitreous luster, hexagonal quartz crystals lining cavities, commonly with white quartz and gray chalcedony or basalt matrix. No cleavage; specific gravity about 2.65.

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals in gas cavities of volcanic basalt, with iron impurities producing the purple color through irradiation and heating. Commonly Cenozoic to Mesozoic in age, depending on locality.

Uses & applications

Used as decorative specimens, bookends, and jewelry; high-quality crystals are collectible, while lower-grade material is used for ornaments and polished slices.

Geological facts

Color intensity varies with iron content and natural irradiation; heating can turn amethyst yellow, producing citrine. The specimens shown are cut or sawn geode sections.

Field identification & locations

Identify by purple quartz crystals, glassy luster, hardness, and a crystalline cavity lining; major sources include Brazil, Uruguay, Zambia, and Mexico. Avoid specimens with uniformly artificial-looking color or coatings.