The Paleolithic period saw the emergence of smaller stone tools that were more delicately worked, including blades, a term that refers to long, thin stone flakes with parallel cutting edges and a length more than twice their width. The earliest blades appeared around 30,000 years ago, made from fine-grained stone such as hornfels, shale, and obsidian. Rather than being used individually, several blades were likely attached to a base of wood or other material, to form a long cutting edge. Blades are considered to be a highly efficient use of stone, since their production yields very little excess material. "