Flint, a form of Silica and variety of quartz, is a durable rock characterized by its hardness and brittleness, allowing the rock to easily break when knapped, a process during which the flint is heated so that it chips more easily, resulting in razor sharp edges. These qualities made flint the primary material with which American Indian peoples manufactured tools and weapons such as knives, arrow and spear heads, and scrapers. There are many Ohio rocks that can be worked into tools such as chert, chalcedony, jasper, and agate, though all these types of stone are generally referred to as flint. However, flint is truly a purer form of chert. In Ohio, flint can be found bedded in layers of limestone or in deposits transported across the state by glaciers. Ohio flint occurs in strata extending from the Brassfield Limestone of the Silurian to Cambridge Limestone, deposited in the tropical seas that once covered Ohio during the Paleozoic Era.
In many ways, the availability of flint contributed to the rich prehistoric and later American Indian populations and their ability to thrive in Ohio. The most popular and prolific flint resource in Ohio is Flint Ridge, a six mile deposit of Pennsylvanian-age Vanport flint, ranging from one to twelve feet deep, spanning parts of eastern Licking and western Muskingum Counties. Flint Ridge was quarried by American Indian tribes for over 12,000 years. With trails leading to the site from every direction, American Indians traveled hundreds of miles to quarry flint to replace broken tools and produce new ones. Not only was Flint Ridge widely visited because of its vast quantities of flint, but the quality of the stone superseded that of any other in the state, and the variety of colors available there, such as green, blue, yellow, pink, and red, due to chemical impurities in the stone, possibly attracted later Woodland tribes like the Adena (850-50 BC) and the Hopewell (150 BC-450 AD). Other flint deposits quarried in Ohio include Zaleski flint in Vinton and Jackson Counties and Upper Mercer flint in Coshocton, Hocking, and Perry Counties. Flint was also an important resource for early European settlers who used flint for fire starters, flintlock guns, and buhrstones, large flat stones used to grind grain in early mills. Today, flint is polished to make jewelry and is recognized as the State of Ohio's official gemstone.