sedimentary
Flint
Cryptocrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness 7 on Mohs scale, dark gray to black color, waxy luster, amorphous crystal structure, conchoidal fracture.
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Physical properties
Hardness 7 on Mohs scale, dark gray to black color, waxy luster, amorphous crystal structure, conchoidal fracture.
Formation & geological history
Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions during the Cretaceous period.
Uses & applications
Historically used for making stone tools and fire-starting; today used in ceramics, abrasives, and decorative building.
Geological facts
Flint produces sparks when struck against steel due to its high hardness and brittle fracture, making it essential for ancient survival.
Field identification & locations
Identify by its distinct conchoidal fracture and waxy luster; commonly found embedded in chalk cliffs or river gravels worldwide.
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