mineral

Amethyst geode fragment

Quartz, SiO₂, purple variety colored by iron impurities

AI-generated identification · may be incorrect

Small polished or broken specimen with white/cream chalcedony or quartz enclosing purple amethyst crystals. Quartz hardness is Mohs 7, vitreous luster, trigonal crystal structure, and no cleavage; the exterior appears rounded and possibly coated or polished.

Identified August 31, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids fill cavities in volcanic rocks, commonly basalt, and amethyst crystallizes during late-stage growth. Most commercial material formed in Cretaceous–younger volcanic provinces, especially Brazil and Uruguay.

Uses & applications

Used for inexpensive jewelry, ornaments, metaphysical collecting, and decorative specimens; this small piece has modest gem value.

Geological facts

Purple color generally results from iron-related defects activated by natural radiation. Color zoning from white chalcedony to purple quartz is typical of amethyst geodes.

Field identification & locations

Identify by testing for glassy quartz luster, hardness, and purple crystal tips lining a cavity; it should scratch ordinary glass but not be scratched by a steel blade. Common sources include Brazil, Uruguay, Zambia, and Mexico.