sedimentary
Flint
Sedimentary cryptocrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, typically dark grey, blue, black, or deep brown with a waxy to vitreous luster, conchoidal fracture, and amorphous or microcrystalline crystal structure.
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Physical properties
Hardness of 7 on the Mohs scale, typically dark grey, blue, black, or deep brown with a waxy to vitreous luster, conchoidal fracture, and amorphous or microcrystalline crystal structure.
Formation & geological history
Formed through the chemical replacement of calcium carbonate in chalk or limestone beds by silica-rich solutions during the Cretaceous period.
Uses & applications
Historically used for making stone tools, arrowheads, and fire-striking; currently used in grinding, decorative landscaping, and occasionally as a building material.
Geological facts
Flint was one of the earliest materials utilized by early humans to create sharp cutting edges and implements due to its predictable conchoidal fracture.
Field identification & locations
Easily identified by its dark color, smooth weathered cortex, conchoidal fracture, and extreme hardness. Commonly found embedded in chalk cliffs or as beach pebbles.
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