sedimentary
River Pebble (Basalt / Greywacke)
Stream-rounded fine-grained rock (Basalt / Metagreywacke)
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
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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.
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