Green-tech metals – the rare earth elements

The 17 metals known as the “rare earth elements” (REEs) are central to green and advanced technologies.

REEs are, in fact, not rare, although they are not common. The term derives from the 1400s, when “rare” meant unusual or strange, and “earth” describes the appearance of REE oxides. The REEs are mostly heavy metals, similar in weight to platinum, gold and lead. To complete the 17, the lighter scandium and yttrium are included, having similar chemical properties to the other REEs.

What are REEs used for?

High-tech uses for REEs include:

  • Magnets, such as for wind turbines (neodymium, praseodymium, dysprosium)

  • Batteries, for hybrid cars (several kilograms of REEs in each car)

  • Electronics (tantalum)

  • High-performance ceramics (yttrium)

  • Phosphors, used in TVs and energy-efficient lamps (europium, terbium)

  • Refrigerants (gadolinium)

  • Superalloys of steel (scandium)

  • Catalysts (cerium, tantalum). These strangely-named metals are technology performance improvers where space is at a premium - in computer hard drives, mobile phones, superconductors, capacitors, hearing aids, pacemakers, lasers, optics, GPS systems, electromagnets.

Where do REEs come from?

REEs are formed in uncommon types of volcanic rock around the globe. Geological processes are usually necessary to concentrate them into mineable deposits. Erosion and weathering of source rock is one avenue, with material carried down rivers and deposited as sediment. Being heavy, REEs accumulate at places where lighter material is carried away, as is the case for alluvial gold. In tropical countries, REEs may be concentrated in old, heavily leached and weathered soils. REEs may also be mined as a low-cost by-product of mining for other metals, such as iron oxide, copper and gold.

 

Updated Oct 2018