sedimentary
Flint
Chert (SiO2)
Hardness: 7 (Mohs scale), Color: Dark grey to black, Luster: Waxy or dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Dark grey to black, Luster: Waxy or dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65
Formation & geological history
Formed as nodules or masses in sedimentary rocks such as chalk and limestone. It is a form of microcrystalline quartz that precipitates from silica-rich fluids during diagenesis.
Uses & applications
Historically used for stone tools (knapping) and starting fires. Modernly used in ceramics, road construction, and as a decorative stone.
Geological facts
Flint was the primary material used by prehistoric humans to create sharp tools. When struck against steel, it produces a spark, which led to its use in flintlock firearms.
Field identification & locations
Identify by its characteristic conchoidal fracture (curved, shell-like breaks) and sharpness. Found globally in chalk and limestone deposits, particularly in Western Europe and the USA.
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