sedimentary
Flint (or Chert)
Silicon Dioxide (SiO2)
Hardness of 7 on the Mohs scale, typically brown, grey, or black with a waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no cleavage, specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically brown, grey, or black with a waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no cleavage, specific gravity of 2.60 to 2.65.
Formation & geological history
Formed as nodules or concretions in sedimentary rocks such as chalk or limestone through the replacement of calcium carbonate by silica-rich solutions during diagenesis, primarily during the Cretaceous period.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-producing fire starters; today used in ornamental stone carving, gravel, and abrasive grits.
Geological facts
Flint was one of the earliest materials manipulated by human ancestors to create sharp cutting tools due to its predictable conchoidal fracture pattern.
Field identification & locations
Easily identified in the field by its waxy luster, conchoidal fracture surfaces, and occurrence as nodules within chalk or limestone formations; commonly found worldwide in sedimentary chalk deposits.
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