sedimentary

Tumbled brown chert or jasper

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown to olive-brown, waxy to dull luster, very fine-grained cryptocrystalline structure, no visible cleavage, and conchoidal fracture. The smooth surface indicates natural water-wear or tumbling/polishing.

Identified August 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or cements sediment, commonly in limestone, volcanic, or siliceous sedimentary environments; iron oxides produce the brown coloration. The specimen’s precise geological age cannot be determined from the image.

Uses & applications

Used for lapidary cabochons, tumbled stones, carvings, and occasionally tools; attractive jasper varieties are collected but are generally inexpensive.

Geological facts

Chert and jasper are chemically similar; jasper is typically more opaque and impurity-rich, while chert may be translucent at thin edges. It can produce a sharp conchoidal edge when freshly fractured.

Field identification & locations

Common in gravel beds, river cobbles, and sedimentary outcrops worldwide; test with a steel file or quartz—true chert/jasper should resist scratching, though surface polish can obscure texture. Exact identification requires a fresh edge or translucency test.