sedimentary
Flint
Cryptocrystalline quartz (SiO2)
AI-generated identification · may be incorrectMohs hardness of 7, vitreous to dull luster, conchoidal fracture, and typically dark gray to black or brown color.
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Physical properties
Mohs hardness of 7, vitreous to dull luster, conchoidal fracture, and typically dark gray to black or brown color.
Formation & geological history
Formed by the replacement of calcium carbonate in limestone by silica-rich groundwater over millions of years.
Uses & applications
Historically used for making stone tools and fire-starting; currently used for decorative landscaping and aggregate.
Geological facts
Flint and chert are chemically identical, but flint traditionally refers to the dark varieties found in chalk formations.
Field identification & locations
Identified easily by its sharp conchoidal fracture and waxy luster, commonly found embedded in chalk or limestone beds.
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