sedimentary
Chert (Flint)
Microcrystalline or cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs), Color: Dark gray to black (flint) or brown/tan, Luster: Waxy to vitreous, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs), Color: Dark gray to black (flint) or brown/tan, Luster: Waxy to vitreous, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in sedimentary environments. Often found as nodules within limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires; currently used as a grinding media in ball mills, in road construction, and for aquarium decor.
Geological facts
Flint was the primary material for prehistoric survival, used to manufacture arrowheads and spear points due to its ability to hold a sharp edge when fractured conchoidally.
Field identification & locations
Identify by its very smooth, waxy surface and distinct shell-like (conchoidal) curves where it has chipped. Commonly found in riverbeds, chalk cliffs, and gravel pits.
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