Lindian Resources has received positive signs from early phase metallurgical testwork at its Kangankunde project in Malawi with results showing concentrate grades of around 60 per cent rare earth oxides (REO).
The company says the test results show that water-only, low-cost gravity and magnetic beneficiation techniques are suitable for recovery of the mineralisation found at the operation.
Recovery ranges for rougher and cleaner stages of shaking table testing for coarse fractions range from 60 per cent up to an impressive 90 per cent. Lindian believes an initial evaluation of the multi-gravity separator (MGS) shows recovery of fine-grained rare earths mineralisation is enhanced over using a shaking table. MGS achieved a 69.7 per cent light rare earths oxide (LREO) recovery to a concentrate grading 51.7 per cent LREO.
Initial wet high intensity magnetic separation (WHIMS) testing also demonstrated increases in the REO grade of a final concentrate to near 60 per cent REO.
The latest testing regime builds on historical metallurgical work conducted at the site in the 1970s that highlighted recovery rates of 60 per cent from a mineral concentrate bearing 60 per cent REO.
Lindian says new gravity recovery technologies – including the multi gravity separator (MGS) that was not developed in the 70s – present an avenue for improved metallurgical recovery.
Evaluation of gravity and magnetic separation techniques – including WHIMS and MGS separators – are the first stage of the metallurgical testwork program. The company says a baseline result of around 70 per cent recovery is an excellent result it will improve upon in subsequent stages of metallurgical testwork.
Lindian Resources chief executive officer Alistair Stephens said: “These early-stage results are exceptionally pleasing and deliver excellent concentrate grades and recoveries from this initial metallurgical testwork. The results benchmark us very well when compared to some of the world’s notable rare earths projects.”
Kangankunde is considered one of the world’s biggest rare earths operations outside China and hosts an outdated resource of 2.53 million tonnes grading 4.24 per cent total rare earths oxide for 107,000 tonnes of contained rare earths when using a cut-off grade of 3.5 per cent. It is a carbonatite-hosted system and notably, the mineralisation is exposed at surface and still open at depth.
The ratio of the highly sought after industrial magnet rare earths, neodymium and praseodymium (NdPr), in the total concentrate at the project is about 19 per cent and a mining licence has already been secured for the site. The explorer says assays show very low levels of nuisance radioactive materials, such as uranium and thorium.
Lindian has secured the use of the only MGS test machine in Perth and will it to undertake extensive further testing. The company says the latest test results are being used to guide the optimisation metallurgical testing program for the planned rare earths concentrate processing plant at Kangankunde which is scheduled to start operating next year.
The explorer has nearly completed phase one of its 12,500m resource definition drill out, including 10,000m of RC drilling and a further 2500m of diamond drilling to test the mineralisation to a depth of 300m. Lindian is already considering phase two of its drill campaign at Kangankunde with two exceptionally deep 1000m drill holes planned to commence in the second half of the year.
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By Michael Philipps
