Sources and Extraction

The minerals bastnaesite and monazite are the chief sources of the rare earths. Much of the rare-earth production in the United States comes from bastnaesite reserves in southern California, the world's largest single-known source of rare-earth elements. Monazite is found in greatest abundance in Australia, Brazil, China, India, Malaysia, and South Africa.

The extraction of rare earths from the minerals in which they are found is a complicated process. First, the minerals are ground to powder and then dissolved in acid. Next, a chemical is added to the solution to cause impurities to settle out. The rare-earth solution is then drawn off, and the rare earths are separated from one another—or groups of rare earths are separated—by the ion: exchange process.

In the ion-exchange process, solutions are filtered through minerals called zeolites, or through synthetic resins that act as zeolites. Zeolites exchange ions (atoms carrying an electrical charge); that is, zeolite ions are added to the solution and rare-earth ions pass into the zeolites. The zeolites are then treated with chemicals that selectively remove various kinds or groups of rare earths.