Green-tech metals – the rare earth elements

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

Consumption is growing by 7.6% a year, at which rate it would double over the next decade. A rush is on globally to find new REE ore deposits, with China possessing 85% of world supply, and consuming 70% of world supply. A “conflict minerals” industry has developed to meet the looming shortage of REEs.

In New Zealand, REE occurrences have been recorded, however, not in mineable deposits to date. 

The REEs are 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.

Uses for REEs

Hi-tech uses for REEs include: magnets, e.g. for wind turbines (neodymium, praseodymium, dysprosium); batteries, e.g. for hybrid cars (several kilograms of REEs in each car); electronics (tantalum); high-performance ceramics (yttrium); and phosphors 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, CD players, mobile phones, superconductors, capacitors, hearing aids, pacemakers, lasers, optics, GPS systems, electromagnets – in short, REEs are seen as necessary to developing the green and clean technologies, for a more sustainable world - provided more of them can be found.

Where do REEs come from?

REEs are formed in uncommon types of volcanic rock, at places 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.

A dark alternative has been to press cheap labour into quarrying and processing, in countries where the rule of law is weak or non-existent. The case par excellence is the Democratic Republic of Congo, where armed militias have been running slave mines, and selling product to electronics manufacturers. This “conflict minerals industry” is clearly important. In 2013 only 7.5% of electronics companies surveyed by US-based HSI said they were ready to comply with a new anti-conflict minerals code, while 35% said they had yet to consider the matter.

All the more reason to look again at REEs in New Zealand, where they have been pinpointed to Northwest Nelson, Westland, Fiordland, and Rakiura/Stewart Island. It is an irony that many of these places are off-limits to mining these sought-after metals, under schedule 4 of the Crown Minerals Act 1991.

Updated Feb 2018