sedimentary

Banded chert or jasper

Microcrystalline quartz (SiO₂), with iron-oxide impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown, ochre, red, and gray bands with a dull to waxy luster. It is cryptocrystalline, lacks visible cleavage, and commonly shows a smooth conchoidal fracture; exact identification is limited by the unpolished surface.

Identified September 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich sediment or volcanic fluids precipitate and replace earlier material, with iron oxides producing the red-brown colors. Most examples are Precambrian to younger, depending on the deposit.

Uses & applications

Used for carving, cabochons, beads, tumbled stones, and lapidary ornaments; historically used for sharp tools and flaked points. Attractive patterned pieces have modest collectible value.

Geological facts

The specimen appears to be a rough, weathered jasper/chert cobble rather than a crystal-bearing rock. Its color zoning likely reflects variable iron-oxide content and silica replacement.

Field identification & locations

Common in gravel beds, volcanic terrains, and sedimentary formations worldwide; test with a steel file or glass, which it should scratch, and inspect a fresh edge for waxy conchoidal fracture. Typical rough specimens sell for about $5–$25; unusually patterned polished material may reach $30–$100.