sedimentary
Flint
SiO2 (Cryptocrystalline Quartz)
Hardness of 7 on the Mohs scale, typically gray, black, or brown in color, waxy to vitreous luster, microcrystalline structure, conchoidal fracture with no true cleavage, and a specific gravity of around 2.6
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Physical properties
Hardness of 7 on the Mohs scale, typically gray, black, or brown in color, waxy to vitreous luster, microcrystalline structure, conchoidal fracture with no true cleavage, and a specific gravity of around 2.6
Formation & geological history
Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich water during the Cretaceous period and other geological epochs
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire; currently used in decorative landscaping, road construction, and occasionally for historical reenactments
Geological facts
Flint and chert are essentially the same mineral, but 'flint' typically refers to the dark varieties found in chalk formations. It was one of the earliest materials manipulated by early humans to create sharp implements.
Field identification & locations
Easily identified by its characteristic smooth, rounded water-worn appearance when found in riverbeds or beaches, its conchoidal fracture showing sharp edges when broken, and its ability to scratch glass
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