sedimentary
Chert / River Pebble
Chert (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan to gray, Luster: dull to waxy, Crystal structure: microcrystalline/cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.6
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan to gray, Luster: dull to waxy, Crystal structure: microcrystalline/cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.6
Formation & geological history
Formed through 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
Historically used for stone tools; currently used in construction aggregate, road surfacing, and decorative landscaping.
Geological facts
Chert was one of the most important raw materials for early humans because of its ability to produce sharp edges when fractured. Flint is a variety of chert.
Field identification & locations
Identify by its hardness (it will scratch glass), rounded tumble-worn shape, and smooth texture. Common in riverbeds and gravel deposits worldwide.
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