sedimentary
Flint
SiO2 (Cryptocrystalline Quartz)
Hardness of 7 on the Mohs scale; varies in color from grey, white, brown to black; waxy to vitreous luster; cryptocrystalline or microcrystalline structure; conchoidal fracture with no cleavage.
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Physical properties
Hardness of 7 on the Mohs scale; varies in color from grey, white, brown to black; waxy to vitreous luster; cryptocrystalline or microcrystalline structure; conchoidal fracture with no cleavage.
Formation & geological history
Formed as nodules and masses in sedimentary rocks such as chalk and limestone through the replacement of calcium carbonate by silica-rich solutions in ancient marine environments.
Uses & applications
Historically used for stone tools, arrowheads, and striking fire; currently used in abrasives, ceramics, and occasionally ornamental or decorative items.
Geological facts
Flint played a critical role in human technological evolution during the Stone Age due to its ability to be chipped into sharp-edged blades and points.
Field identification & locations
Easily identified by its conchoidal fracture, sharp edges when broken, and ability to spark when struck against steel. Commonly found in chalk deposits worldwide.
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