By Kenneth Jessen
In its simplest terms, an arrastra is a grinder and dates back thousands of years. The grinding surface is typically flat bedrock situated near a stream. A vertical pocket is drilled into the rock, and a perpendicular pole is placed in the pocket. Attached to the pole near its base is a horizontal beam and attached to the beam, usually by chains, is a heavy stone that does the grinding. Farther up the pole is a long horizontal beam that is used to turn the arrastra. As the pole is rotated, ore is placed in the path of the stone and the ore is crushed against the bedrock. Eventually, this process creates a groove in the bedrock that is telltale evidence that an arrastra once existed.