sedimentary
Flint
SiO2 (Cryptocrystalline Quartz)
Hardness of 7 on the Mohs scale; color typically gray, dark brown, or black; waxy to vitreous luster; cryptocrystalline structure; exhibits conchoidal fracture with sharp edges; specific gravity around 2.6.
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Physical properties
Hardness of 7 on the Mohs scale; color typically gray, dark brown, or black; waxy to vitreous luster; cryptocrystalline structure; exhibits conchoidal fracture with sharp edges; specific gravity around 2.6.
Formation & geological history
Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions in marine environments during the Cretaceous and other periods.
Uses & applications
Historically used for making stone tools, arrowheads, and spark generation in firearms; today largely collected as a specimen or used in decorative landscaping and specialized grinding.
Geological facts
Flint has been utilized by humans for over two million years due to its ability to fracture conchoidally into extremely sharp edges, making it essential for early survival and technology.
Field identification & locations
Easily identified by its smooth, weathered exterior, waxy interior fracture surfaces, conchoidal breakage, and ability to scratch glass. Found globally in chalk and limestone deposits.
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