sedimentary
River Pebble (Quartzite or Chert)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Brownish-tan; Luster: Dull to waxy; Structure: Microcrystalline; Specific Gravity: 2.6-2.7; Shape: Well-rounded/elipsoidal due to water erosion.
- Hardness
- 6
- Color
- Brownish-tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brownish-tan; Luster: Dull to waxy; Structure: Microcrystalline; Specific Gravity: 2.6-2.7; Shape: Well-rounded/elipsoidal due to water erosion.
Formation & geological history
Formed through the deposition of silica-rich sediments or the metamorphism of sandstone, subsequently eroded and rounded by the action of moving water in a river or stream bed over thousands of years.
Uses & applications
Commonly used in landscaping, road construction (as aggregate), aquarium decor, or as basic 'worry stones' for collectors.
Geological facts
The smooth, rounded shape is a result of fluvial abrasion, where constant tumbling against other rocks in water wears down sharp edges. This specific brownish hue often comes from trace amounts of iron oxide (limonite) staining.
Field identification & locations
Identify by its smooth texture and high hardness (cannot be scratched by a steel knife). Commonly found in current or ancient riverbeds, beaches, and glacial till.
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