sedimentary
Flint
SiO2 (Cryptocrystalline Quartz)
Hardness of 7 on the Mohs scale, dark gray to black color with a waxy to vitreous luster, microcrystalline crystal structure, exhibits prominent conchoidal fracture, and a specific gravity of around 2.60.
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Physical properties
Hardness of 7 on the Mohs scale, dark gray to black color with a waxy to vitreous luster, microcrystalline crystal structure, exhibits prominent conchoidal fracture, and a specific gravity of around 2.60.
Formation & geological history
Formed as nodules in sedimentary rocks such as chalk and marine limestones through the replacement of calcium carbonate by silica-rich solutions millions of years ago.
Uses & applications
Historically used for making stone tools, weapons, and fire-starting flint-and-steel sets; currently used in decorative aggregates, road construction, and occasionally in lapidary work.
Geological facts
Flint was one of the earliest materials manipulated by human ancestors due to its ability to fracture into extremely sharp edges, a process known as knapping.
Field identification & locations
Easily identified in the field by its conchoidal fracture showing sharp edges, waxy luster, and dark coloration, frequently found along chalk cliffs and beaches.
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