Rare earth elements

are vital in green technologies, including magnets for wind turbines, hybrid-car batteries, LED lamps, medical equipment and electronics like smart phones, tablets and TVs.

There are a total of 16 naturally occurring rare earth elements. 14 within the chemical group called lanthanides, plus yttrium and scandium. The latter are considered rare earth elements because they tend to occur in the same ore deposits as the lanthanides, and exhibit similar chemical properties. REEs are found as components in several minerals, the most important sources being bastnäsite, monazite and xenotime.

These minerals typically comprise several percentages by weight of REEs. Dependent on the specific ore, the distribution between the different REEs may differ substantially. The 16 REEs all tend to occur together in the same mineral deposits. To separate them into single elements of high purity is challenging and expensive due to their chemical similarity.