sedimentary

Tumbled jasper or chert

Microcrystalline quartz (SiO₂), likely jasper/chert; exact identification is uncertain from the photograph

AI-generated identification · may be incorrect

Opaque brown to olive-tan, smooth tumbled surface, waxy to dull luster, and subtle flow-like banding. Hardness is approximately 6.5–7 Mohs; no visible cleavage, conchoidal fracture when broken, and specific gravity about 2.6.

Identified September 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement sediments, commonly incorporating iron oxides that produce brown coloration. These varieties formed during the geological history of their host sedimentary formations, generally ranging from Precambrian to younger ages.

Uses & applications

Used as ornamental stone, cabochons, beads, carvings, and decorative polished specimens; it has little industrial value compared with ordinary quartz or aggregate.

Geological facts

Jasper is an opaque, impure variety of chalcedony, while chert is a broader name for dense microcrystalline quartz. The specimen’s rounded shape indicates human tumbling rather than natural weathering alone.

Field identification & locations

Common in gravel deposits and silica-rich sedimentary terrains worldwide, including the western United States, Australia, Brazil, and Africa. A glass-scratch test, performed cautiously, can distinguish it from softer rocks: it should scratch ordinary glass, while a steel blade generally will not scratch it.