sedimentary
Chert / Flint
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, colors range from white, grey, brown to black, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with no cleavage, specific gravity of 2.60-2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white, grey, brown to black, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with no cleavage, specific gravity of 2.60-2.65.
Formation & geological history
Formed via chemical and biochemical processes in marine environments, typically through the replacement of calcium carbonate in limestone by silica-rich solutions over millions of years.
Uses & applications
Historically used for stone tools and weapons due to its sharp conchoidal fracture. Today used in abrasives, road aggregate, and historically for flintlock firearms.
Geological facts
Chert and flint are essentially the same material; 'flint' usually refers to darker varieties found in chalk or marl formations, while 'chert' refers to varieties found in limestone.
Field identification & locations
Easily identified by its characteristic conchoidal fracture and high hardness (scratches glass). Commonly found globally within sedimentary rock formations, especially chalk and limestone beds.
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