Problems in the processing of rare earths- the importance of mineralogy

Less than half a century ago the rare earth elements (REE) were classed as minor metals - who had even heard of neodymium, now essential in the production of powerful rare earth permanent magnets, used in wind turbines and many other applications?  Processing of REE now features in many major conferences, and in November, in Cape Town, MEI will introduce a new conference, Developments in the Processing of the "Hi-Tech" Metals (Hi-Tech Metals '18), where REE processing will be a major topic.

Hi-Tech Metals '18 immediately follows Process Mineralogy '18, the 5th in the series, and appropriately a keynote lecture at this conference will review common problems, and progress towards solutions, in the processing of REE.

The geochemistry and mineralogy of REE deposits is diverse and ranges from carbonatite-related deposits and alkaline rocks to mineral sands, ion adsorption clays, marine crusts, nodules and clays, by-products of phosphate and bauxite, and re-use of waste materials. Despite the large number of recent exploration projects, very little additional REE production has started. An in-depth understanding of the mineralogy is essential for process design and all of the deposit types have mineralogical advantages and challenges, which will be reviewed and explained in the keynote. For example, the deposits with the best established processing routes are monazite-bearing mineral sands but monazite radioactivity renders most unusable. Ion adsorption clays are easily leachable but deposits are low grade and shallow so new environmentally-friendly leaching techniques are needed. The diverse mineralogy of alkaline rocks has required development of processing routes for rare minerals such as steenstrupine and eudialyte. Carbonatites tend to have high proportions of the least valuable, lightest REE in REE fluorcarbonates or monazite. A deposit with two ore minerals, REE fluorcarbonate and apatite, that combine to give a REE profile close to that required by industry has an advantage if the ore minerals can be recovered efficiently.

The keynote lecture will be given by Frances Wall, Professor of Applied Mineralogy at the Camborne School of Mines (CSM), University of Exeter, UK. She has a BSc in Geochemistry and PhD from the University of London and worked on petrology and applied mineralogy at the Natural History Museum, London before joining CSM in 2007. Her research interests include the geology, applied mineralogy, processing, and responsible sourcing of critical raw materials. Frances currently leads two large international projects: SoS RARE and HiTech AlkCarb, was Head of CSM from 2008-2014, and was named one of the 100 Global Inspirational Women in Mining 2016.

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