mineral

Chalcedony geode or quartz-rich agate nodule

Microcrystalline quartz, SiO₂, with possible crystalline quartz druse

AI-generated identification · may be incorrect

Typically white to gray, translucent, and waxy to glassy; hardness about 6.5–7 Mohs, no cleavage, conchoidal fracture, and specific gravity near 2.6. The rounded exterior and sparkling cavity suggest a small geode or agate nodule.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater filled cavities or vesicles in volcanic rock, depositing chalcedony and later quartz crystals. Such nodules commonly formed during the Cenozoic or Mesozoic, depending on locality.

Uses & applications

Used as lapidary material, cabochons, polished specimens, and decorative stone; attractive drusy interiors have modest collector value.

Geological facts

Chalcedony is cryptocrystalline quartz, while geodes develop hollow or partly hollow interiors lined with crystals. The specimen appears naturally rounded and weathered, possibly tumbled or cut open.

Field identification & locations

Identify by its glassy/waxy silica texture, lack of cleavage, hardness sufficient to scratch glass, and quartz sparkle in cavities; common sources include Brazil, Uruguay, Mexico, and the western United States.