Flint (or flintstone) is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. Flint is usually dark grey, black, green, white, or deep brown in colour, and often has a waxy appearance. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. From a petrological point of view, "flint" refers specifically to the form of chert which occurs in chalk or marly limestone. Similarly, "common chert" (sometimes referred… (More on Flint)