sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs), Color: Dark grey to black, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs), Color: Dark grey to black, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed from the accumulation of siliceous remains of organisms or precipitation of silica-rich fluids in sedimentary basins. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) and fire-starting. Used today in road construction, as decorative stone, and in some ceramics.
Geological facts
Flint is a variety of chert that was essential to prehistoric humans because it breaks into very sharp edges through a process called knapping.
Field identification & locations
Identify in the field by its distinctive curved (conchoidal) fracture surfaces and its ability to scratch glass. Found globally in sedimentary environments.
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