sedimentary
Chert (Flint)
Silicon dioxide (SiO2)
Hardness of 7 on the Mohs scale, typically white, grey, brown, or black in color, waxy to vitreous luster, microcrystalline or cryptocrystalline structure, conchoidal fracture with no true cleavage, and a specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically white, grey, brown, or black in color, waxy to vitreous luster, microcrystalline or cryptocrystalline structure, conchoidal fracture with no true cleavage, and a specific gravity of 2.60 to 2.65.
Formation & geological history
Formed through the chemical or biochemical precipitation of silica from aqueous solutions, often replacing carbonate rocks like limestone during diagenesis. Commonly found within chalk or limestone formations and dates across various geological eras.
Uses & applications
Historically used for making stone tools, arrowheads, and spark generation in firearms. Today used in abrasives, ceramics, and as a decorative or collection specimen.
Geological facts
Ancient humans prized chert and flint for its sharp conchoidal fracture, which allows it to be knapped into extremely sharp edges and points for hunting and survival tools.
Field identification & locations
Identified easily by its waxy luster, conchoidal fracture surfaces, and high hardness capable of scratching glass. Found globally in sedimentary strata, particularly marine limestone and chalk deposits.
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