Chert

A coarse type of siliceous (silica) rock, a form of quartz, used for the manufacture of stone tools where flint was not available. It is of poorer quality than flint, formed from ancient ocean sediments and often has a semi-glassy finish. It is pinkish, white, brown, gray, or blue-gray in color. Flint, chert, and other siliceous rocks like obsidian are very hard, and produce a razor-sharp edge when properly flaked into tools. This crystalline form of the mineral silica is found as nodules in limestones. Varieties of chert are jasper, chalcedony, agate, flint, and novaculite. Chert and flint provided the main source of tools and weapons for Stone Age man.

A very finely crystalline form of the mineral silica, found as nodules in limestones. Many cherts are so fine-grained that they behave like a glass — they fracture almost as sharply as obsidian, and may be chipped or flaked to make artefacts. All have been used as materials for making artefacts, but the most commonly used has been the particularly glassy variety called flint, which is found in the chalk of England and Europe.