mineral

Quartz geode (likely amethyst-bearing)

Silica geode; quartz, SiO₂, with possible amethyst and minor iron oxides

AI-generated identification · may be incorrect

A hollow volcanic-rock cavity lined with sparkling quartz crystals; gray-white chalcedony and drusy quartz surround darker purple areas. Quartz is Mohs 7, vitreous-lustrous, trigonal, with indistinct cleavage and specific gravity about 2.65.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when gas bubbles in basaltic lava become lined with silica-rich groundwater; later quartz crystallizes inward, sometimes with purple amethyst from iron impurities and irradiation. The host cavity is commonly Cenozoic to Mesozoic in age, depending on locality.

Uses & applications

Used as a decorative specimen, display geode, lapidary material, and occasionally in jewelry; it has little industrial value in this form.

Geological facts

Breaking or sawing a geode reveals an interior that may be hollow, quartz-filled, or partially filled with other minerals. Purple color is strongest where iron-bearing quartz formed under suitable redox conditions.

Field identification & locations

Identify it by a rounded, weathered exterior and a crystal-lined interior; quartz scratches glass and shows hexagonal crystal faces. Common sources include Brazil, Uruguay, Mexico, Morocco, and the United States.