sedimentary
Flint
SiO2 (Cryptocrystalline Quartz)
Hardness of 7 on the Mohs scale, typically brown to grayish-black color, waxy to vitreous luster, microcrystalline or cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically brown to grayish-black color, waxy to vitreous luster, microcrystalline or cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.
Formation & geological history
Formed through the chemical replacement of limestone or chalk by silica-rich groundwaters in marine environments, predominantly during the Cretaceous period.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire. Modern uses include abrasives, decorative aggregates, and specialty construction.
Geological facts
Flint is famous for its ability to produce sparks when struck against steel, which made it essential for early firearms and fire-making.
Field identification & locations
Easily identifiable in the field by its characteristic conchoidal fracture, sharp edges when broken, waxy luster, and occurrence as nodules within chalk or limestone formations.
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