sedimentary

Smooth gray river pebble

Likely fine-grained sandstone or siltstone; exact identification requires a fresh surface and tests

AI-generated identification · may be incorrect

Medium gray, rounded and water-worn, dull earthy luster, very fine granular texture with small pits; likely Mohs hardness about 5–7. No visible crystals or cleavage; specific gravity approximately 2.3–2.7.

Identified August 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably a sedimentary clast eroded from bedrock and rounded in a river, stream, or beach. Its depositional age cannot be determined from the photograph and may range from young sediment to ancient sedimentary rock.

Uses & applications

Primarily a natural collectible, landscaping stone, or craft pebble; fine-grained varieties may be useful as aggregate. It is not gem-quality based on appearance.

Geological facts

The rounded shape and uniformly weathered surface indicate prolonged abrasion rather than deliberate shaping. The pale gray color may reflect quartz, feldspar, clay minerals, or carbonate cement.

Field identification & locations

Check a fresh chip: sandstone feels gritty and shows grains, while limestone fizzes with dilute hydrochloric acid and is softer. A steel nail or glass-scratch test can help estimate hardness; common sources include streambeds, beaches, and glacial deposits.