sedimentary
Flint
SiO2 (Cryptocrystalline Quartz)
Hardness of 7 on the Mohs scale, typically brown, gray, or black, waxy or vitreous luster, microcrystalline 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, gray, or black, waxy or vitreous luster, microcrystalline structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.
Formation & geological history
Formed as nodules or masses in sedimentary rocks such as chalk and marine limestones through the replacement of calcium carbonate by silica-rich solutions diagenetically.
Uses & applications
Historically used for making stone tools, weapons, and fire-striking implements; modern uses include landscaping and as decorative or educational specimens.
Geological facts
Flint breaks with a characteristic conchoidal fracture, producing extremely sharp edges that made it invaluable to early humans for tool-making.
Field identification & locations
Can be identified by its conchoidal fracture, waxy luster, and high hardness capable of scratching glass. Commonly found globally in chalk formations and limestone deposits.
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