Gold (Aurum) is a metallic element with the symbol of Au and the atomic number of 79. The simple substance (free form) of gold, commonly known as gold, is a precious metal, which has been used as currency, preservation and jewelry for many centuries. In nature, gold exists in the form of simple substance in gold nuggets or rocks, underground veins and alluvium. Gold is also one of the currency metals. Gold is solid at room temperature, with high density, softness, brightness and corrosion resistance. It is the metal with the best ductility, second only to platinum.