mineral

Botryoidal chalcedony/geode fragment

Microcrystalline quartz, SiO₂, likely chalcedony with drusy quartz

AI-generated identification · may be incorrect

White to pale gray, waxy-to-glassy luster with sparkly crystalline cavities; quartz has Mohs hardness 7, no cleavage, conchoidal fracture, and specific gravity about 2.6. The rounded, bubbly texture is botryoidal and the vugs may contain tiny quartz crystals.

Identified August 24, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed when silica-rich groundwater filled cavities in volcanic rock, depositing chalcedony and later drusy quartz. The specimen’s exact geological age and locality cannot be determined from the photograph.

Uses & applications

Used as a decorative and lapidary material, including cabochons, carvings, bookends, and specimen pieces; this rough fragment has limited jewelry value.

Geological facts

Chalcedony is quartz whose crystals are too small to see individually; botryoidal surfaces resemble a cluster of small bubbles or grapes. White chalcedony may be called quartz geode material when it preserves a cavity.

Field identification & locations

Identify it by its very hard, non-cleaving silica texture, rounded botryoidal crust, and crystal-lined cavities; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, Mexico, and the western United States.