mineral

Amethyst geode

Quartz, SiO₂; purple variety colored mainly by iron impurities and irradiation

AI-generated identification · may be incorrect

Hardness 7 Mohs; vitreous luster; purple quartz crystals lining a cavity, with gray chalcedony or quartz rind. Quartz is trigonal and lacks cleavage, showing conchoidal fracture; specific gravity about 2.65.

Identified August 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals inside cavities, commonly volcanic gas bubbles, in basalt. Many commercial specimens formed during the Cretaceous–Cenozoic, especially in South America, though age varies by locality.

Uses & applications

Used for jewelry, ornaments, meditation stones, and mineral collecting; cut geodes and polished crystal surfaces are decorative rather than major industrial materials.

Geological facts

Amethyst’s color ranges from pale lilac to deep violet and can fade with prolonged heat or sunlight. The specimen appears cut and polished around a druzy crystal-lined cavity.

Field identification & locations

Identify it by purple, glassy quartz crystals lining a rounded hollow, often surrounded by banded gray chalcedony. Major sources include Brazil, Uruguay, Zambia, and Bolivia; value is driven by saturation, crystal size, aesthetics, and intactness.