sedimentary
Flint / Chert
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, typically dark grey to black or brown, waxy to vitreous luster, conchoidal fracture with sharp edges, no cleavage, specific gravity around 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically dark grey to black or brown, waxy to vitreous luster, conchoidal fracture with sharp edges, no cleavage, specific gravity around 2.60 to 2.65.
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 stone tools, arrowheads, and fire-starting (striking against steel); currently used in abrasives, ceramics, and ornamental lapidary work.
Geological facts
Flint is famous for its ability to fracture conchoidally, producing extremely sharp edges that made it vital to early human technology during the Stone Age.
Field identification & locations
Easily identified in the field by its dark color, smooth or nodular exterior, waxy luster, and characteristic conchoidal fracture. Commonly found embedded in chalk or limestone formations worldwide.
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