sedimentary
Chert / Flint
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale, typically brown, tan, grey or black in color, waxy to vitreous luster, conchoidal fracture with sharp edges, specific gravity around 2.60.
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Physical properties
Hardness of 7 on the Mohs scale, typically brown, tan, grey or black in color, waxy to vitreous luster, conchoidal fracture with sharp edges, specific gravity around 2.60.
Formation & geological history
Formed via the chemical replacement of limestone or chalk by silica-rich solutions or through the accumulation of siliceous skeletal remains of marine organisms over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-striking fire starters; currently used in abrasives, road aggregate, and historically in flintlock firearms.
Geological facts
Chert is extremely durable and resistant to weathering, which is why ancient stone tools made of chert often survive intact in the archaeological record for thousands of years.
Field identification & locations
Can be identified in the field by its distinct conchoidal fracture (smooth, curved breakage patterns), high hardness that scratches glass, and waxy luster. Commonly found nodules within sedimentary limestone formations worldwide.
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