sedimentary
River Rock (likely Siltstone or fine-grained Sandstone)
Clastic Sedimentary Rock
Hardness: 6-7 on Mohs scale; Color: Earthy brown with dark manganese oxide staining or algal growth; Luster: Dull/Earthy; Crystal structure: Non-crystalline (granular/clastic); Cleavage: None; Specific gravity: Approx 2.6.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Earthy brown with dark manganese oxide staining or algal growth; Luster: Dull/Earthy; Crystal structure: Non-crystalline (granular/clastic); Cleavage: None; Specific gravity: Approx 2.6.
Formation & geological history
Formed through the accumulation and cementation of silt and sand-sized mineral particles. The rounded edges indicate 'rounding' through water transport in a river or stream environment.
Uses & applications
Common river rocks are used extensively in landscaping, garden paths, drainage systems, and as aggregate for concrete in the construction industry.
Geological facts
The smooth, rounded shape is the result of 'abrasion'—the mechanical scraping of a rock surface by other rocks and sediments during transport by water currents.
Field identification & locations
Identify in the field by its smooth, water-worn texture and lack of sharp edges. These are ubiquitous in riverbeds, glacial deposits, and coastal areas.
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