sedimentary
Chert (Flint Nodule)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Brown, black, tan with white weathering (cortex), Luster: Waxy to vitreous, Structure: Cryptocrystalline, Fracture: Conchoidal
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Physical properties
Hardness: 7 (Mohs scale), Color: Brown, black, tan with white weathering (cortex), Luster: Waxy to vitreous, Structure: Cryptocrystalline, Fracture: Conchoidal
Formation & geological history
Formed as nodules or beds in sedimentary rocks like limestone or chalk through the accumulation of silica-rich microfossils or chemical precipitation.
Uses & applications
Historically used for stone tools and starting fires; currently used in jewelry (as jasper/agate variants) and as decorative gravel.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges for hunting and scraping.
Field identification & locations
Identify by its waxy appearance and the shell-like (conchoidal) curves that form when it breaks. Found worldwide in sedimentary basins.
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