sedimentary

Tumbled brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque reddish-brown, fine-grained, and dull to subtly waxy. It has no visible cleavage, conchoidal fracture, and likely specific gravity near 2.6; the rounded surface appears naturally water-worn or tumbled.

Identified September 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica replaces or accumulates in marine or freshwater sediment, while jasper is an iron-rich opaque variety; formation ages range widely from Precambrian to recent. The pebble was later rounded by stream or beach abrasion.

Uses & applications

Used for flaked stone tools, carving, cabochons, beads, lapidary pieces, and decorative aggregate; it has little industrial value in small specimens.

Geological facts

Its brown-red color commonly comes from iron oxides, especially hematite. A steel file generally struggles to scratch it, while quartz can scratch glass.

Field identification & locations

Common in gravel beds, river channels, beaches, and sedimentary terrains worldwide; identify by its dense uniform texture, waxy luster, and conchoidal fracture. The image alone cannot distinguish chert from jasper confidently.