sedimentary
Flint (or Chert with Chalk/Limestone)
Microcrystalline quartz (SiO2) nodule
Hardness of 7 on the Mohs scale; color varies from dark grey, black, to white due to chalk/limestone encrustation; waxy to dull luster; cryptocrystalline structure; conchoidal fracture with no cleavage.
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Physical properties
Hardness of 7 on the Mohs scale; color varies from dark grey, black, to white due to chalk/limestone encrustation; waxy to dull luster; cryptocrystalline structure; conchoidal fracture with no cleavage.
Formation & geological history
Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions in marine environments over millions of years during the Cretaceous period.
Uses & applications
Historically used for making stone tools, arrowheads, and spark generation in firearms. Modern uses include abrasive grinding, landscaping, and decorative aggregates.
Geological facts
Flint was one of the most vital materials for early human survival, used extensively for creating sharp-edged cutting tools and weapons due to its unique conchoidal fracture pattern.
Field identification & locations
Easily identified by its characteristic smooth, water-worn exterior often showing contrasting dark flint and white chalky cortex, extreme hardness, and conchoidal fracture when broken. Found worldwide in chalk formations and river gravels.
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