sedimentary
River Pebbles / Mudstone
Sedimentary Rock / Silty Claystone
Hardness: 3-5 Mohs. Color: Brownish-grey, dark grey, tan. Luster: Dull to earthy, resinous when wet. Texture: Fine-grained, smooth rounded pebbles from stream erosion.
- Hardness
- 3-5 Mohs
- Color
- Brownish-grey, dark grey, tan
- Luster
- Dull to earthy, resinous when wet
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Physical properties
Hardness: 3-5 Mohs. Color: Brownish-grey, dark grey, tan. Luster: Dull to earthy, resinous when wet. Texture: Fine-grained, smooth rounded pebbles from stream erosion.
Formation & geological history
Formed through the compaction and cementation of fine-grained clay and silt sediments in low-energy aquatic environments, later weathered and water-worn in riverbeds or streams.
Uses & applications
Commonly used in landscaping, river rock aggregate for construction, decorative gravel, and educational soil study collections.
Geological facts
River pebbles get their smooth, rounded shapes from natural mechanical abrasion as water rolls them downstream over long periods of time.
Field identification & locations
Identified by smooth rounded edges, fine-grained earthy matrix, and soft to medium hardness. Found abundantly along riverbanks, creek beds, and alluvial plains.
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