metamorphic or sedimentary
River Pebble (Quartzite or Chert)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs), Color: Gray and yellow/tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Gray and yellow/tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of sandstone (quartzite) or the accumulation of silica in sedimentary environments (chert). This specific pebble has been smoothed and rounded by water erosion in a river or coastal environment.
Uses & applications
Common river stones are used for landscaping, decorative gravel, aquarium substrate, and small-scale ornamental crafts.
Geological facts
The yellow banding suggests iron oxide staining. River pebbles illustrate the rock cycle by showing how larger rock masses are physically weathered over centuries into smooth, rounded shapes.
Field identification & locations
Identify by its rounded, smooth texture and high hardness (cannot be scratched by a steel knife). Commonly found in riverbeds, glacial deposits, and beaches globally.
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