Arrastras like this one were used by the earliest hard-rock miners in this area to grind gold ore. People skilled in stone cutting made them for the miners from local rock. This arrastra was chiseled by hand from blocks of hard granite. Several blocks were shaped and then fitted together. The miners put gold-bearing rock in the trough. It then was crushed by dragging the boulder on the chain over it, freeing the gold. Often a horse was harnessed to the wooden arm and provided the power by walking in a circle around the arrastra. Some were operated by water power. Arrastras were crude, but good enough until roads and the railroad were built into this area. The mines then could be supplied with better, factory-made equipment and the arrastras quickly became historical curiosities.