sedimentary
River Pebble (Quartz/Chert)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs. Color: Milky white, tan, and grey. Luster: Waxy to dull due to weathering. Crystal Structure: Microcrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Milky white, tan, and grey
- Luster
- Waxy to dull due to weathering
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Physical properties
Hardness: 6.5-7 Mohs. Color: Milky white, tan, and grey. Luster: Waxy to dull due to weathering. Crystal Structure: Microcrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich sediments or the erosion of quartz veins, subsequently smoothed and rounded by the mechanical action of water in a river or stream environment over thousands of years.
Uses & applications
Primarily used as decorative landscaping stones, aquarium gravel, or as a source for polishing in rock tumblers. Larger deposits are used in construction aggregate.
Geological facts
These specimens show classic well-rounded morphology, indicating they have traveled a long distance from their source rock. Pebbles like these are often found in ancient riverbeds that are now miles away from current water sources.
Field identification & locations
Identify by the smooth, rounded 'potato' shape and inability to be scratched by a steel knife. These are ubiquitous in glacial till, riverbanks, and beaches worldwide.
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