The rare earth elements (REE) have been the headline of the critical metals agenda for the last decade, and remain important due to their use in many technologies associated with low-carbon energy and transport. In 2010 China produced almost all of the world’s REE supply; by 2015, its share was 85%, and the latest USGS figures suggest it now produces only 63%. Is this diversification of supply associated with more responsible resources?
The REE can be sourced from two types of geological deposits: 1) hard-rock deposits formed by high-temperature magmatic and hydrothermal processes, including alkaline rocks and carbonatites as well as vein-type deposits; and 2) deposits formed by low-temperature processes, including mineral sands and ion adsorption clays. Additionally, the REE can be the main product of a mine, or can be produced as by-products of a major mineral. In China’s Bayan Obo mine, the REE are by-products of iron ore extraction.
Each deposit type has different pros and cons as a source of the REE (1). Grade and tonnage are part of the story, but there are other critical issues such as the balance of the different REE, and the minerals in which the REE are contained. Ease of processing, amount of radioactivity, and type of mining can all impact on the viability of an REE mine.
So how have REE sources changed in the last ten years? A substantial part of global REE supply still comes from carbonatite mines in China, including Bayan Obo and the Mianning-Dechang REE belt. Alkaline rocks and carbonatites are the main sources of REE from Russia and the USA, whilst the upper weathered sections of carbonatites are mined in Australia, Brazil and Burundi. Most of these mines are run on a relatively large-scale, and governed by national regulations. However, a substantial proportion of the world’s REE comes from mineral sands and ion adsorption clay-type deposits, mined at a range of scales in countries including China, India, Myanmar, and Thailand. Many of these ores are exported directly to China for processing and separation. Environmental regulations for mining in China have become much more stringent in recent years, meaning that official production of the REE is well managed. However, although there is little published information, news stories suggest that some operations in China and elsewhere are still considered environmentally damaging and in some cases illegal, meaning that diversification of supply has not necessarily led to more responsible sourcing. Interestingly, one option for sourcing of the REE that has not progressed far past research and pilot-scale is the possibility of extraction as a by-product of phosphate or aluminium mining.
[1] Wall, F, Rollat, A and Pell, R (2017): Responsible Sourcing of Critical Metals. Elements 13, 313-318.
Biography
Kathryn Goodenough is a Principal Geoscientist at the British Geological Survey, and Deputy Director, BGS Global.Her current research focuses on the geology and resources of critical metals, with particular interests in the rare earth elements and lithium. She also leads a BGS capacity-building programme, funded by the UK Department for International Development, which focuses on working with partners in developing countries to improve aspects of governance in the mineral resources sector.
Kathryn Goodenough, British Geological Survey, Edinburgh, UK, kmgo@bgs.ac.uk
David Merriman, Roskill, London, UK
Frances Wall, Camborne School of Mines
Eimear Deady
The SoS RARE team
Any questions: hello@responsiblerawmaterials.com
