The first use of metals in prehistoric times involved those few metals that can be found nearly pure on the earth’s surface, including copper and electrum (a natural alloy of gold and silver). When the supplies of easily found metals were exhausted, ancient peoples learned to dig into the earth to find more. The digging tools were rudimentary sticks or bones. Adding stone and later metal heads to digging tools made them more useful and long lasting. The development of the pickaxe greatly improved the digging power of a man by allowing greater force to be applied at the point of impact.