sedimentary
Chert
Microcrystalline Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Red-brown/earthy; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)
- Hardness
- 6
- Color
- Red-brown/earthy
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Red-brown/earthy; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed from the accumulation of siliceous remains of marine organisms or chemical precipitation from hydrothermal fluids in sedimentary basins.
Uses & applications
Historically used for stone tools (arrowheads); currently used in road construction, as decorative stone, and in glass manufacturing.
Geological facts
Chert is so hard that it can strike sparks against steel, and it was a vital resource for prehistoric humans due to its sharp conchoidal edges when fractured.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and smooth, shell-like fracture surfaces. Often found in limestone beds.
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Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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