sedimentary
Chert (Pebble)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Grayish-brown to dark gray; Luster: Waxy to dull; Fracture: Conchoidal; Structure: Microcrystalline/Cryptocrystalline quartz
- Hardness
- 6
- Color
- Grayish-brown to dark gray
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Grayish-brown to dark gray; Luster: Waxy to dull; Fracture: Conchoidal; Structure: Microcrystalline/Cryptocrystalline quartz
Formation & geological history
Formed through the accumulation and precipitation of silica-rich biogenic ooze or chemical replacement in marine sedimentary environments. Subsequently rounded and smoothed by water erosion.
Uses & applications
Historically used for flintknapping to make tools and weapons; currently used for river rock gravel, tumbling, and general geological study.
Geological facts
Chert is a hard, fine-grained sedimentary rock composed of microcrystals of quartz. Smooth, water-worn chert pebbles like this are frequently found in riverbeds and along beaches.
Field identification & locations
Identify in the field by its hardness (scratches glass), smooth waxy feel, and characteristic curved conchoidal fracture edges. Widely found in gravel bars, stream beds, and ocean coastlines globally.
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