sedimentary

Polished river pebble

Indeterminate fine-grained fluvial clast, likely sandstone or chert

AI-generated identification · may be incorrect

Smooth, rounded, olive-brown, opaque, and wet-looking with a fine-grained surface and dull-to-waxy luster. Apparent hardness is approximately 5–7 Mohs; no visible crystals or cleavage. Exact identification requires an unstained, dry surface and hardness testing.

Identified September 21, 2026More sedimentary →

Explore Polished river pebble in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Rounded by prolonged abrasion in a stream or river; its original lithology may be sedimentary, volcanic, or metamorphic. Geological age cannot be determined from the photograph.

Uses & applications

Primarily used for decoration, landscaping, crafts, and collecting; it has little industrial or jewelry value unless testing reveals attractive chert, jasper, or another lapidary material.

Geological facts

The smooth form is a classic water-worn cobble, and the intense shine is largely caused by surface water or oil rather than natural luster.

Field identification & locations

Dry it and inspect for grain, banding, conchoidal fracture, or translucency; a steel nail tests roughly 5.5 Mohs, while glass tests about 5.5. Common sources include river gravels, beaches, and commercial polished-stone assortments.