Stone Age devices, usually flint (seechert 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 sandstones, quartzites, 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 alsostone-tool industry.