sedimentary
River Stone/Chert Pebble
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to light brown; Luster: Waxy to dull; Texture: Smooth, water-worn surface; Cleavage: None (conchoidal fracture)
- Hardness
- 7 on Mohs scale
- Color
- Tan to light brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to light brown; Luster: Waxy to dull; Texture: Smooth, water-worn surface; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed via the accumulation of silica-rich microfossils or chemical precipitation in marine or freshwater environments. This specific specimen has been rounded by fluvial (river) erosion.
Uses & applications
Commonly used in landscaping, construction aggregate, and as decorative gravel. Smooth pebbles are often used in aquariums or for stone painting and crafts.
Geological facts
Chert and flint were among the first materials used by early humans for tools because of their hardness and the way they break into sharp edges. Smooth river stones can travel hundreds of miles from their source.
Field identification & locations
Identify by its smooth, rounded shape and extreme hardness (will scratch glass). Commonly found in riverbeds, glacial deposits, and along coastlines.
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