sedimentary

Polished river cobble, likely jasper or iron-stained chert

Microcrystalline quartz (SiO₂), potentially hematite/goethite-bearing

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, opaque to slightly translucent, with waxy to dull luster; red-orange coloration reflects iron oxides, while gray areas may be silica-rich chert. The rounded shape and smooth surface indicate natural water abrasion or polishing.

Identified September 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed as silica-rich sediment or chemically altered rock, with iron minerals later producing the red-orange staining; its precise geological age and source formation cannot be determined from the photograph. It was transported and rounded in a stream or river.

Uses & applications

Jasper and chert are used for carvings, cabochons, beads, tumbling, knife edges, and decorative stone; this small cobble has modest collector value.

Geological facts

The specimen appears to be a stream-worn pebble rather than a crystal-bearing mineral. Stronger identification would require a fresh fracture, streak test, hardness test, and examination for conchoidal fracture.

Field identification & locations

Common in gravel bars worldwide, especially areas draining volcanic or iron-rich formations; test whether it scratches glass and leaves no colored streak. Avoid destructive testing if it is a valued find.