sedimentary

Polished brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown to reddish-brown, opaque, and glassy to waxy luster. It has an extremely fine-grained microcrystalline quartz structure, with no visible cleavage and conchoidal fracture; polishing accounts for the smooth surface.

Identified September 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich fluids replace or cement sediment, commonly from biogenic silica; jasper is an iron-impure variety producing red-brown colors. Formation can range from Precambrian to recent sedimentary environments.

Uses & applications

Used for decorative stones, cabochons, beads, knife tools, and polishing specimens; generally modest jewelry and collector value.

Geological facts

The specimen’s rounded shape and glossy finish indicate natural water abrasion followed by human polishing or tumbling. Iron oxides commonly create its warm brown coloration.

Field identification & locations

Identify it by its uniform fine texture, lack of visible grains, hardness sufficient to scratch glass, and conchoidal fracture; common in river gravels and sedimentary terrains worldwide.