sedimentary
Chert / Flint
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, typically earthy to vitreous luster, conchoidal fracture, colors range from white to gray, brown, and black, cryptocrystalline structure with no visible crystal faces.
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Physical properties
Hardness of 7 on the Mohs scale, typically earthy to vitreous luster, conchoidal fracture, colors range from white to gray, brown, and black, cryptocrystalline structure with no visible crystal faces.
Formation & geological history
Formed by the chemical precipitation of silica from aqueous solutions or the replacement of calcium carbonate in limestone by silica-rich fluids, often found in marine sedimentary environments over various geological ages.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire due to its sharp conchoidal fracture; occasionally used in decorative landscaping and lapidary work.
Geological facts
Chert and flint are essentially the same material, with 'flint' typically referring to darker varieties found in chalk or marly limestone formations. It was one of the most important materials for early human technology.
Field identification & locations
Easily identified in the field by its hardness (scratches glass), waxy or dull luster, and distinctive conchoidal (shell-like) fracture edges. Commonly found as nodules within limestone or chalk deposits worldwide.
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