sedimentary
Flint / Chert
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale, dark grey to brown color, waxy or vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.60-2.65.
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Physical properties
Hardness of 7 on the Mohs scale, dark grey to brown color, waxy or vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.60-2.65.
Formation & geological history
Formed via chemical precipitation of silica-rich fluids within chalk or limestone formations during the Cretaceous period, replacing carbonate minerals.
Uses & applications
Historically used for prehistoric stone tools, fire-starting, and flintlock firearms; today collected as a geological specimen and used in landscaping.
Geological facts
Flint produces sparks when struck against steel due to iron micro-particles shearing off and igniting in the air, making it vital for ancient survival.
Field identification & locations
Easily identifiable in the field by its distinct conchoidal (shell-like) fracture, waxy luster, and high hardness that easily scratches glass.
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