flint variety of quartz that commonly occurs in rounded nodules and whose crystal structure is not visible to the naked eye. Flint is dark gray, smoky brown, or black in color; pale gray flint is called chert. When found in chalk or in other rocks containing lime, the nodules frequently have a white coating. Flint is translucent to opaque. It was early used by primitive peoples for making knives and spearheads because, although it is very hard, it is more readily shaped than stone; edges can be flaked off with comparative ease, especially those of freshly dug pieces, by pressure exerted with... Read more