sedimentary
Flint / Chert
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale, typically dark grey, black, or brown with a waxy to vitreous luster, conchoidal fracture, and no true cleavage.
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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, conchoidal fracture, and no true cleavage.
Formation & geological history
Formed through the chemical replacement of limestone or chalk by silica-rich groundwater, or from the accumulation of siliceous skeletal remains of marine organisms over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire; currently used for abrasive grit, road aggregate, and ornamental lapidary work.
Geological facts
Flint is extremely durable and has been utilized by humans for prehistoric stone tools since the Stone Age due to its predictable conchoidal fracture.
Field identification & locations
Found worldwide in chalk and limestone formations. It can be identified in the field by its smooth, weathered outer cortex, dark vitreous interior, and sharp edges when fractured.
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