Grain Mortar

an implement for milling grain by hand. It consists of two stones—a lower stone with a flat, slightly concave surface and an upper one, smaller and rounded. The grain is poured into the lower stone and ground by the upper one. Grain mortars appeared in the early Neolithic period and were used until the invention of round millstones in the fourth and third centuries B.C. Grain mortars continue to be used among some peoples of Africa, Australia, and Central America.