sedimentary

River Pebble (Basalt / Greywacke)

Stream-rounded fine-grained rock (Basalt / Metagreywacke)

AI-generated identification · may be incorrect

Hardness: 6-7 Mohs. Color: Dark grey to brownish-grey with subtle sheen. Luster: Dull to sub-vitreous. Texture: Smooth, water-worn, fine-grained surface.

Hardness: 6-7 Mohs
Color: Dark grey to brownish-grey with subtle sheen
Luster: Dull to sub-vitreous

Identified July 23, 2026More sedimentary →

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Physical properties

Hardness: 6-7 Mohs. Color: Dark grey to brownish-grey with subtle sheen. Luster: Dull to sub-vitreous. Texture: Smooth, water-worn, fine-grained surface.

Formation & geological history

Formed through mechanical weathering and stream transport. Rocks are eroded from parent outcrops and naturally rounded by rolling in riverbeds or coastal environments over long periods.

Uses & applications

Commonly used as decorative river stone, landscaping gravel, aquarium substrate, and for stone carving or meditation stones.

Geological facts

Smooth river stones acquire their rounded shape purely from continuous friction against water, sand, and other stones over thousands of years.

Field identification & locations

Identified by its smooth, rounded morphology without sharp edges, uniform fine-grained surface, and high density. Found along riverbanks, beaches, and glacial deposits globally.