sedimentary
Chert (Flint)
Silicon dioxide (microcrystalline quartz, SiO2)
Hardness of 7 on the Mohs scale, grayish-brown to white color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with very sharp edges, specific gravity of 2.60 to 2.65
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Physical properties
Hardness of 7 on the Mohs scale, grayish-brown to white color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with very sharp edges, specific gravity of 2.60 to 2.65
Formation & geological history
Formed by the chemical precipitation of silica from aqueous solutions or the replacement of calcium carbonate in limestone by silica-rich groundwaters, often found in marine sedimentary environments over millions of years
Uses & applications
Historically used for making stone tools, arrowheads, and spark generation in firearms; occasionally used in ornamental carvings, lapidary arts, and road construction
Geological facts
Chert and flint are chemically identical forms of microcrystalline quartz, traditionally distinguished by color where darker varieties were called flint and lighter ones chert. It was one of the most critical materials for early human technological development due to its predictable conchoidal fracture.
Field identification & locations
Can be identified in the field by its characteristic smooth, waxy luster, conchoidal fracture patterns, and high hardness capable of scratching glass. Commonly found interbedded in limestone or chalk deposits worldwide.
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