mineral

Tumbled chalcedony (likely agate or jasper fragment)

Microcrystalline quartz, SiO₂ (chalcedony)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent gray-brown to honey coloration with a waxy luster and curved, conchoidal fractures. The rounded surface appears naturally or artificially tumbled, with possible iron-oxide staining and subtle banding/inclusions.

Identified August 16, 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 microcrystalline quartz over geologic time, commonly from the Cenozoic or older. Exact identification and age require magnification or testing.

Uses & applications

Used for cabochons, beads, carvings, lapidary specimens, and decorative stone; ordinary pieces have modest value.

Geological facts

Chalcedony is quartz made of interlocking microscopic crystals rather than visible crystal faces. The specimen may be a weathered or tumbled agate fragment, but the photograph does not show enough banding for a secure variety identification.

Field identification & locations

Common in volcanic terrains, river gravels, and desert alluvial deposits worldwide, especially Brazil, Uruguay, Mexico, the western United States, and Madagascar. A glassy luster, conchoidal fracture, translucency, and inability to scratch it with a steel nail support chalcedony; quartz or glass testing may be needed.