A metallic element, constituting the most precious metal used as a common commercial medium of exchange. It has a characteristic yellow color, is one of the heaviest substances known (specific gravity 19.32), is soft, and very malleable and ductile. It is quite unalterable by heat, moisture, and most corrosive agents, and therefore well suited for its use in coin and jewelry. Symbol Au (Aurum). Atomic weight 196.7.