mineral

Tumbled chalcedony (likely moss or plume variety)

Microcrystalline quartz, SiO₂

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent gray-brown body with white branching or cloudlike inclusions, waxy to vitreous luster, and no visible cleavage. Its rounded, wet-looking surface indicates natural water wear or tumbling.

Identified September 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly during the Cenozoic or earlier; inclusions may be quartz, calcite, or iron/manganese oxides. The specimen is polished or naturally waterworn.

Uses & applications

Used for beads, cabochons, carvings, and ornamental pieces; attractive patterned material has modest lapidary value.

Geological facts

Chalcedony is fibrous cryptocrystalline quartz, so individual crystals are generally invisible. Similar gray material may be called “common chalcedony,” moss agate, or plume agate depending on the inclusion pattern.

Field identification & locations

Identify it by its translucent edge, waxy luster, conchoidal fracture, lack of cleavage, and ability to scratch ordinary glass; it commonly occurs in volcanic terrains and gravel deposits. Exact variety cannot be confirmed from the image alone.