sedimentary
Chert (River Pebble)
Microcrystalline silica (SiO2)
Hardness: 6.5-7 Mohs; Color: Brownish-gray with white flecks; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Brownish-gray with white flecks
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brownish-gray with white flecks; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, subsequently rounded by water erosion in a river or glacial setting.
Uses & applications
Commonly used in road construction, landscaping, and historically for stone tools due to its sharp edges when broken.
Geological facts
Chert is a variety of quartz. It was one of the most important materials for early humans to create arrowheads, scrapers, and fire-starting tools.
Field identification & locations
Identify by its hardness (it can scratch glass) and smooth, water-worn texture. Found globally in riverbeds, beaches, and glacial till.
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