sedimentary
Flint
Cryptocrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, typically brown to dark grey, waxy to vitreous luster, conchoidal fracture with sharp edges, and no cleavage.
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Physical properties
Hardness of 7 on the Mohs scale, typically brown to dark grey, waxy to vitreous luster, conchoidal fracture with sharp edges, and no cleavage.
Formation & geological history
Forms by the replacement of calcium carbonate by silica in chalk or limestone formations during the Cretaceous period.
Uses & applications
Historically used for making stone tools and fire-starting; today primarily used in decorative landscaping, flint-knapping, and abrasives.
Geological facts
Ancient humans prized flint for its ability to fracture into extremely sharp blades, making it vital for survival tools.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and ability to spark when struck against steel. Found globally in chalk deposits.
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