Stone Age devices, usually flint (see chert and flint ), shaped by flaking off small particles or by breaking off a large flake to use as a tool .
Prehistoric humans preferred flint and similar siliceous stones because of the ease with which they could be chipped and for their sharp cutting edges. They also used quartzites , {{link=quartz">quartz , obsidian , and volcanic rocks. Stone tools were chipped by striking a block of flint with a hammer of stone, wood, or bone or by striking the block itself on the edge of a fixed stone. Pressure flaking consists of applying pressure by means of a pointed stick or bone near the edge of a flake or blade, to detach small flakes, and was used mostly to put the finishing touches on tools. See also stone-tool industry .