sedimentary
River Stone (Quartzite/Chert mixture)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, tan, and grey banding; Luster: Dull to waxy; Structure: Finely crystalline; Cleavage: None/Conchoidal fracture.
- Hardness
- 6
- Color
- Brown, tan, and grey banding
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, and grey banding; Luster: Dull to waxy; Structure: Finely crystalline; Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed through the accumulation of silica-rich sediments or the metamorphism of sandstone, subsequently weathered and rounded by water transport in a river or stream environment.
Uses & applications
Used in landscaping, decorative river rock arrangements, aggregate for construction, and as a pocket stone for collectors.
Geological facts
These smooth shapes are the result of 'saltation,' where rocks bounce along riverbeds, chipping away sharp edges over centuries. Many such stones contain trace iron oxides giving them their brownish hue.
Field identification & locations
Identify by its smooth, rounded 'potato' shape and hardness (it will scratch glass). Common in fluvial deposits and glacial till globally.
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