gemstone

Amethyst cluster/geode fragment

Quartz, SiO₂; purple variety amethyst, with possible druzy quartz and iron-oxide staining

AI-generated identification · may be incorrect

Typically Mohs hardness 7, vitreous luster, translucent purple crystals, hexagonal crystal structure, and no prominent cleavage; the orange-brown base likely contains iron oxides or host rock. The image is somewhat obscured, so exact mineral identification is approximate.

Identified August 16, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals in cavities of volcanic rocks, commonly basalt; iron impurities create the purple color. Most commercial amethyst formed in Mesozoic–Cenozoic volcanic provinces, though age varies by locality.

Uses & applications

Used as a decorative specimen, carving material, and gemstone; clusters are popular in collections and interior décor. It has little industrial value compared with ordinary quartz.

Geological facts

Amethyst’s color can fade with prolonged heating or strong sunlight and may become yellow citrine when heated. Large Brazilian and Uruguayan geodes are especially famous.

Field identification & locations

Identify by purple, glassy quartz crystals with hardness near 7 that scratch glass but not readily with a steel knife. Common sources include Brazil, Uruguay, Zambia, and Mexico.