The Probert Encyclopaedia of Rocks & Minerals

FLINT

Flint is a massive compact variety of quartz comprised of fine grained silica. It is usually grey to brown or nearly black in colour and breaks with a conchoidal fracture and sharp edge. It is amorphous, and usually occurs in nodules or rounded lumps. Its surface is generally uneven, and covered with a whitish rind or crust, the result of weathering or of the action of water percolating through the rocks. It is very hard, and strikes fire with steel, and is an ingredient in glass and in all fine pottery ware. Its true native place is the upper bed of the chalk formation, in which it is formed as a series of concretions, the silica in sponges and in other marine animals which lived on the sea floor while the chalk was being deposited being attracted into nodules.
Research Flint