sedimentary
Flint nodule
Sedimentary cryptocrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, dark brown to black exterior weathering to white, waxy to vitreous luster, conchoidal fracture with no cleavage, specific gravity around 2.60.
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Physical properties
Hardness of 7 on the Mohs scale, dark brown to black exterior weathering to white, waxy to vitreous luster, conchoidal fracture with no cleavage, specific gravity around 2.60.
Formation & geological history
Formed through the replacement of calcium carbonate in chalk or limestone by silica-rich solutions during diagenesis in ancient marine environments, typically Cretaceous period.
Uses & applications
Historically used for prehistoric stone tools, fire-starting, and early firearms; currently used in aggregate, abrasive manufacturing, and by lapidary collectors.
Geological facts
Flint is extremely durable and breaks with sharp conchoidal edges, making it one of the most important materials for early human technological development.
Field identification & locations
Commonly found embedded in chalk cliffs or as beach pebbles in coastal areas with chalk geology. Easily identified by its conchoidal fracture and waxy luster.
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