sedimentary

Tumbled red-brown chert or jasper

Microcrystalline quartz (SiO₂), likely iron-stained chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; reddish-brown, opaque, with a smooth tumbled surface and dull to waxy luster. It has cryptocrystalline quartz structure, no obvious cleavage, and typically specific gravity near 2.6.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement sediment, often with iron oxides producing the red color; commonly Paleozoic or younger, depending on locality. The rounded form is human-tumbled or naturally water-worn.

Uses & applications

Used as ornamental stone, cabochons, beads, carvings, lapidary material, and occasionally as a durable aggregate. It has modest collector value unless unusually patterned or locality-specific.

Geological facts

Jasper is technically an opaque, impure variety of microcrystalline quartz, while chert is commonly more uniform and gray or brown; the boundary between them is gradual.

Field identification & locations

Identify it by its opaque red-brown body, very fine texture, waxy luster, and inability to scratch with a steel knife easily; it should scratch glass. Common in gravel beds and silica-rich sedimentary formations worldwide.