sedimentary
Flint / Chert Nodule
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, varies in color from grey, brown, white to black, amorphous or cryptocrystalline crystal structure.
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Physical properties
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, varies in color from grey, brown, white to black, amorphous or cryptocrystalline crystal structure.
Formation & geological history
Formed in marine environments by the replacement of calcium carbonate with silica-rich solutions within chalk or limestone formations during the Cretaceous period and other geological eras.
Uses & applications
Historically used for stone tools, fire-starting, and weaponry; currently used in abrasives, road construction, and as ornamental or specimen stones.
Geological facts
Flint nodules often form around fossils or organic remains in chalk beds. When fractured, it breaks with sharp conchoidal edges, making it ideal for knapping.
Field identification & locations
Easily identified by its distinctive conchoidal fracture, waxy luster, and high hardness capable of scratching glass. Commonly found weathering out of chalk cliffs and limestone streams.
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