sedimentary
Flint
SiO2 (Microcrystalline Quartz / Chert)
Hardness of 7 on the Mohs scale, typically dark grey, black, or brown with a waxy to vitreous luster, cryptocrystalline structure, and conchoidal fracture.
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Physical properties
Hardness of 7 on the Mohs scale, typically dark grey, black, or brown with a waxy to vitreous luster, cryptocrystalline structure, and conchoidal fracture.
Formation & geological history
Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions in marine environments over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire; currently used in decorative landscaping, road construction, and grinding mills.
Geological facts
Flint was one of the earliest materials mastered by early humans for toolmaking due to its predictable conchoidal fracture which allows for sharp, precise edges.
Field identification & locations
Can be identified in the field by its dark, smooth weathered exterior, conchoidal fracture showing a sharp edge, and high hardness capable of scratching glass.
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