sedimentary
Chert (White Chert/Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Creamy white to light gray, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Creamy white to light gray, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms or through biochemical precipitation in sedimentary rock layers, often occurring as nodules in limestone or chalk.
Uses & applications
Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as a source of silica.
Geological facts
Chert breaks with a conchoidal fracture, creating very sharp edges, which made it the primary material for prehistoric tools and weapons.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like fracture surfaces. Often found in riverbeds or eroding out of limestone cliffs.
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