flint

Flint is a hard, cryptocrystalline form of quartz and a variety of chert. It is mainly composed of microcrystalline silica (SiO2) and forms as nodules within carbonate rocks, most famously the chalk of Europe. Flint nodules develop when silica-rich fluids fill voids in chalk and precipitate microcrystalline quartz, producing a rock with a dark gray to black color and a waxy or vitreous luster. Weathered surfaces often reveal a lighter rind.

Flint is known for its conchoidal fracture and its ability to be knapped into sharp edges, a property that made it a dominant material for lithic tools across prehistoric societies. In archaeology, flint was used to manufacture cores, flakes, scrapers, blades, and arrowheads. Flintknapping techniques are studied to understand early technology and behavior.

In addition to toolmaking, flint is historically associated with fire-starting. In the form of a nodular rock, it was struck against steel to produce sparks that could ignite tinder, a method used in the flint and steel fire-starting set and in early firearms, where a flintlock mechanism relied on a flint striking steel to ignite powder.

Distinctions within terminology note that flint refers to the chalk-associated variety common in Europe, while the broader term chert covers similar microcrystalline silica rocks found worldwide. Flint typically occurs in nodules with a dark interior and a pale weathered exterior, reflecting varying iron content and other impurities.