sedimentary
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Dark brown to black, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
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Physical properties
Hardness: 7 (Mohs scale), Color: Dark brown to black, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
Formation & geological history
Formed through the accumulation of siliceous remains such as radiolaria or diatoms in marine environments, or from the chemical precipitation of silica-rich fluids. Can be found in rocks from the Precambrian era to the present.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges; currently used for decorative purposes, landscape stone, and as a raw material for silicon production.
Geological facts
Chert produces sparks when struck against steel, leading to its widespread use in flintlock firearms. It was one of the first materials traded over long distances by prehistoric humans.
Field identification & locations
Identify in the field by its hardness (scratches glass) and its curved, shell-like (conchoidal) fracture pattern. Commonly found in limestone or chalk beds.
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