sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Brown to grey, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline quartz, Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: Brown to grey, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline quartz, Cleavage: None (conchoidal fracture)
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolarians or diatoms) or via chemical precipitation in limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons (arrowheads); currently used in road construction and as a gemstone (jasper/agate variants).
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges, revolutionizing prehistoric toolmaking.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and curved, glass-like fracture surfaces. Often found as nodules within carbonate rocks like limestone.
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