sedimentary

Rounded river pebble, likely weathered sandstone or volcanic rock

Indeterminate fine-grained lithic clast; possible sandstone (quartz-rich)

AI-generated identification · may be incorrect

Gray-brown, fine-grained, dull to slightly earthy luster, and smoothly water-worn with a pale weathering patch. Hardness is approximately 5–7 depending on composition; no visible cleavage or crystals, and specific gravity is likely about 2.4–2.8.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as a natural rock and rounded by prolonged abrasion in a stream, river, or shoreline environment. Its original geological age cannot be determined from the photograph.

Uses & applications

Primarily a decorative, educational, or collecting specimen; similar pebbles may be used in landscaping, crafts, and aggregate.

Geological facts

The dark granular surface and rounded shape are consistent with a fine-grained sandstone, basaltic rock, or altered volcanic fragment, but the image does not support a precise identification.

Field identification & locations

Look for grain size, reaction to dilute hydrochloric acid, streak, and hardness: sandstone feels gritty and may scratch glass, while basalt is denser and typically dark gray. Common in river gravels worldwide.