1. Chromium, which is used in stainless steel, tool steel and for high-temperature applications. Since 1961, the U.S. has relied 100% on other nations for chromium.
Going forward, the Republic of South Africa and Zimbabwe contain a staggering 98% of the world's reserves of this mineral.
2. Cobalt – Cobalt-based superalloys are used primarily in gas turbines and jet engines. Cobalt has not been mined in the U.S. since 1971 because the amount that the U.S. can produce cannot compete with the price from other countries.