English: Chert is a microcrystalline to cryptocrystalline, quartzose sedimentary rock. It can be any color, is hard, breaks with conchoidal fracture, and has sharp, broken edges. Chert can be biogenic in origin, formed from the remains of once-living organisms that had siliceous skeletons (like hexactinellid sponges or radiolarians). It can also have a chemical origin, formed by precipitation from diagenetic or basinal fluids that have moved through rocks. Some cherts are altered, deeply-buried opalite or geyserite deposits. It has been hypothesized that certain chert occurrences are altered, eolian, quartzose silt deposits on ancient shallow seafloors.

Chert is also known as "flint" - the two terms are synonymous. Asserted differences between chert and flint include: 1) Chert is light-colored and flint is dark-colored. 2) Chert is chemical in origin and flint is biogenic in origin. 3) Chert is the name of the rock and flint is the name of an archaeological artifact (like an arrowhead) composed of chert.

4) Chert is low-quality, in terms of impurities, and flint is high-quality.