mineral

Tumbled chalcedony (likely yellow/brown jasper or agate)

Microcrystalline quartz, SiO₂ (chalcedony; variety uncertain)

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; honey-yellow to brown, translucent to opaque, with a waxy-to-glassy luster and conchoidal fracture. No visible cleavage; cryptocrystalline quartz texture and typical specific gravity near 2.6.

Identified September 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, precipitating as chalcedony, jasper, or agate. Such material commonly formed during Mesozoic–Cenozoic volcanic activity, though the specimen’s exact age cannot be determined visually.

Uses & applications

Used as a decorative and lapidary stone for tumbling, cabochons, carvings, beads, and small ornaments; massive low-grade material has little industrial use.

Geological facts

The brown-yellow coloration may come from iron oxides or hydroxides. The smooth rounded shape and polish indicate human tumbling, while the internal fracture is natural or polishing-related.

Field identification & locations

Identify by its hardness, waxy appearance, lack of cleavage, and inability to scratch it with a steel blade easily; quartz should scratch ordinary glass. Common sources include volcanic regions of Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.