sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Dark grey to brown with waxy luster, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Dark grey to brown with waxy luster, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation within limestone/chalk beds; ages vary from Archean to recent.
Uses & applications
Historically used for stone tools (arrowheads, knives) and strike-a-lights; currently used in jewelry (as jasper), road surfacing, and as a raw material for ceramics.
Geological facts
Flint is a specific variety of chert often found in chalk or marly limestone; it was 'man's first technology' as it allowed for the creation of sharp tools through knapping.
Field identification & locations
Identify by its characteristic waxy appearance and shell-like (conchoidal) fractures with sharp edges. Found worldwide in sedimentary basins, especially in chalk cliffs.
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