Strategic minerals are minerals essential to national defense—the supply of which a country uses but cannot produce itself. A third to a half of the 80 minerals used by industry could be classed as strategic minerals. Wealthy countries, such as the United States, stockpile these minerals to avoid any crippling effect on their economy or military strength if political circumstances were to cut off their supplies. The United States, for instance, stockpiles bauxite (10.5 million metric dry tons), manganese (1.7 million metric tons), chromium (1.4 million metric tons), tin (59,993 metric tons), cobalt (189 metric tons), tantalum (635 tons), palladium (1.25 million troy ounces), and platinum-group metals (platinum—4,704 kilograms, palladium—16,715 kilograms and iridium—784 kilograms).