sedimentary

River Rock (likely Siltstone or fine-grained Sandstone)

Clastic Sedimentary Rock

AI-generated identification · may be incorrect

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

Identified April 11, 2026More sedimentary →

Explore River Rock (likely Siltstone or fine-grained Sandstone) in the encyclopedia →

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Physical properties

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.