sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs, Color: Brown/tan with white bands, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 Mohs, Color: Brown/tan with white bands, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formation occurs as silica-rich fluids precipitate within limestone or chalk beds, often replacing organic matter. Found globally in sedimentary strata from Precambrian to Cenozoic eras.
Uses & applications
Historically used for stone tools and weaponry (arrowheads); currently used in road construction, as jewelry accents (beads), and striking surfaces for fire-starting.
Geological facts
Flint is a variety of chert that produces sparks when struck against steel. It was one of the first materials used by early humans for tool-making due to its sharp conchoidal edges.
Field identification & locations
Identify by its characteristic curved (conchoidal) shell-like fracture and ability to scratch glass. Common in riverbeds and chalk cliffs. Collectors look for unique banding or color patterns.
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