sedimentary
River Pebbles (Chert and Quartzite)
Sedimentary Clastic Rock (Silica-rich)
Hardness: 6.5-7 (Mohs scale); Color: tan, brown, grey, cream, and reddish-orange; Luster: matte to waxy; Structure: microcrystalline or granular; Shape: rounded to sub-rounded due to water erosion.
- Hardness
- 6
- Color
- tan, brown, grey, cream, and reddish-orange
- Luster
- matte to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: tan, brown, grey, cream, and reddish-orange; Luster: matte to waxy; Structure: microcrystalline or granular; Shape: rounded to sub-rounded due to water erosion.
Formation & geological history
Formed through the weathering and erosion of larger rock masses, transported by rivers and streams. These specific specimens are primarily made of microcrystalline quartz (chert) or metamorphosed sandstone (quartzite) that has been tumbled by water over thousands of years.
Uses & applications
Commonly used in landscaping, aquarium decor, drainage systems, decorative pathways, and as a raw material for construction aggregates.
Geological facts
The rounded shape is a direct result of 'abrasion' during transport in water. Geologists use the roundness of these pebbles to determine how far the sediment has traveled from its source.
Field identification & locations
Identify by their smooth, rounded surface and high hardness (most will scratch glass). They are found globally in riverbeds, beaches, and glacial deposits. Look for a 'waxy' texture upon close inspection of chert pieces.
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