The West Coast’s mineral-rich, black sands are yielding encouraging levels of enrichment in rare earth elements, including within minerals not normally associated with them, such as epidote, ilmenite and zircon. NZIMMR’s search for REEs is extending to mineral sands, and elsewhere in New Zealand.
Neodymium, dysprosium and lanthanum are among the high-value REEs found in West Coast mineral sand deposits, starting a conversation on how to make their recovery economic. NZIMMR is increasing the visibility of these green-tech metals, to spark renewed interest in them. For its part, the Government wants to encourage an REE-based industry in New Zealand. Among questions are where they occur, in potentially economic quantities, and how to reduce the cost and environmental impacts of separating them from other minerals, to produce concentrates.
Part of the journey is gaining a better insight into REE mineralogy in West Coast minerals sands. Allanite contains around 20% REE expressed as an oxide, monazite, 60%, and xenotime, 80%, alongside the more common minerals in black sands. To mine once, and recover all the minerals is one approach to reducing costs of extraction, for example, the mineral sand fraction won from alluvial gold mining.
Key research questions for NZIMMR are to understand the minerals associated with the REEs and the chemistry of these minerals and find ways of isolating the individual rare earth elements. Led by Dr John Youngson, NZIMMR’s team on this project includes Kirsty Hollis and Dr Shaun Hayton.
Encouraging results from the analysis of splits separated from samples collected for NZIMMR’s enhancing gold recovery project prompted systematic sampling from the seashore to the upper edge of the beach at selected West Coast beaches. Samples were screened and split at NZIMMR’s Waimatuku research facilities to enable REE analysis by size fraction (SGS Laboratories), and mineralogy by size fraction in collaboration with New Zealand universities.
This work has shown that REEs are substantially enriched in West Coast mineral sands and concentrated from parts per million to per cent levels in certain heavy minerals in these deposits. The next challenges include how to separate selected heavy minerals to create intermediate products for further processing, and how to separate the relevant REEs from these products for use in green technology applications in New Zealand, and/or for export.