sedimentary
General Gravel (River Rock/River Stones)
Mixed Lithic Sediments (Conglomerate Clasts)
Hardness: Varied (usually 5.5-7 Mohs); Color: Tones of brown, tan, grey, and ochre; Luster: Dull to earthy; Crystal Structure: Mostly microcrystalline; Cleavage: None/Irregular; Specific Gravity: Approx 2.6-2.7.
- Hardness
- Varied (usually 5
- Color
- Tones of brown, tan, grey, and ochre
- Luster
- Dull to earthy
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Physical properties
Hardness: Varied (usually 5.5-7 Mohs); Color: Tones of brown, tan, grey, and ochre; Luster: Dull to earthy; Crystal Structure: Mostly microcrystalline; Cleavage: None/Irregular; Specific Gravity: Approx 2.6-2.7.
Formation & geological history
Formed through the mechanical weathering and erosion of pre-existing rocks (igneous, metamorphic, and sedimentary). These pieces have been smoothed and rounded by the action of moving water in rivers or streams over hundreds to thousands of years.
Uses & applications
Used primarily in landscaping, drainage systems, construction aggregate, aquarium substrate, and decorative garden paths. Larger or more colorful specimens may be used for rock painting.
Geological facts
River rocks are often found in 'alluvial deposits.' They tell the geological story of the upstream environment from which they were washed. Their smooth edges are a result of 'attrition,' where rocks collide and wear each other down while being transported by water.
Field identification & locations
Identify by their smooth, rounded edges and water-worn surfaces. Commonly found in riverbeds, lake shores, and glacial till. Collectors can find them anywhere there is current or historical water flow.
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