sedimentary
Chert / Flint
Cryptocrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, various colors including white, grey, brown, and black, microcrystalline crystal structure.
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Physical properties
Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, various colors including white, grey, brown, and black, microcrystalline crystal structure.
Formation & geological history
Formed by the chemical precipitation of silica from aqueous solutions or the replacement of limestone or chalk by silica-rich fluids during diagenesis.
Uses & applications
Historically used for making stone tools and weapon points due to its sharp conchoidal fracture; occasionally used in decorative items or abrasive products.
Geological facts
Chert is extremely durable and weather-resistant, which is why prehistoric stone tools made of chert often survive in pristine condition for thousands of years.
Field identification & locations
Easily identified in the field by its hard conchoidal fracture, dull-to-waxy luster, and tendency to produce sharp edges when struck. Found globally within sedimentary limestone and chalk formations.
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