mineral

Quartz geode (likely amethyst-bearing)

Microcrystalline quartz and crystalline quartz (SiO₂), with possible iron-oxide staining

AI-generated identification · may be incorrect

Hardness 7; white, cream, lavender-purple, and rusty yellow-brown colors; vitreous to sugary luster; quartz crystals line a cavity, with no obvious cleavage. Specific gravity is about 2.65.

Identified August 16, 2026More mineral →

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Physical properties

Hardness 7; white, cream, lavender-purple, and rusty yellow-brown colors; vitreous to sugary luster; quartz crystals line a cavity, with no obvious cleavage. Specific gravity is about 2.65.

Formation & geological history

Formed when silica-rich groundwater deposited quartz crystals inside a gas vesicle or cavity in volcanic rock, commonly basalt. Geodes typically formed during volcanic episodes from the Mesozoic to Cenozoic, depending on locality.

Uses & applications

Used as a decorative specimen, lapidary material, and occasional jewelry stone; attractive amethyst interiors have greater value than ordinary quartz geodes.

Geological facts

The purple color, if present, comes mainly from iron impurities and irradiation. The yellow-brown areas are likely iron oxides or included clay rather than a separate gemstone.

Field identification & locations

Identify by the hollow or vuggy interior and radiating quartz crystals; amethyst is confirmed by distinct purple coloration and quartz hardness. Common sources include Brazil, Uruguay, Mexico, and the United States.