sedimentary

River Pebble (Quartz/Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

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

Identified June 19, 2026More sedimentary →

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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.