Northern Minerals Ltd (ASX:NTU) has tested its heavy rare earth ore sorting system on the largest orebody at Browns Range Heavy Rare Earth Project pilot plant in northern Western Australia.
The Australian heavy rare earths producer is one of only a few producers of heavy rare earth element dysprosium outside of China.
Dysprosium is used in the production of DyNdFeB (dysprosium neodymium iron boron) magnets used in clean energy, military and high technology solutions.
NTU started production of heavy rare earth carbonate in late 2018 as part of pilot assessment of economic and technical feasibility of a larger scale development at Browns Range, however, it wasn’t until this year that the ore sorter was installed and commissioned.
NTU is producing ore sorted material and converting this to a 30% TREO (total rare earth oxide) concentrate in its’ Browns Range beneficiation plant.
The sorter will also be tested for its economic and technical feasibility at the front end of the pilot plant.
Northern Minerals aims to build the Western Australian operation into a significant world producer of dysprosium outside of China.
Sorter tested on largest orebody
NTU announced today that it had completed a bulk sample test on 4,479 tonnes of ore from Wolverine, the largest orebody at Browns Range.
Test results show a 45% grade increase to the mill and more than 95% TREO recovery when feeding a 0.9% TREO Wolverine ore to the ore sorter circuit.
Bulk sample tests highlighted additional key factors to consider for ore sorting that are not apparent from small scale tests.
"Positive bulk sample tests"
“The construction, commissioning and testing of the ore sorter circuit marks another milestone in the development of the Browns Range Project,” Northern Minerals’ CEO Mark Tory said.
“The positive bulk sample tests confirm the effectiveness of the ore sorting circuit on the Wolverine ore to significantly increase the head grade to the mill which is expected to result in higher production rates and lower operating costs for a full-scale operation at Browns Range.”
Further to this, initial ore sorting tests on Banshee material shows amenability to sorting, with further test-work planned.
Effective sorting of the lower grade Banshee material has the potential to increase the Browns Range ore reserve estimate.
Of the Banshee test-work, Tory said, “It’s also pleasing to see the initial ore sorting tests the Banshee ore showing promise which, if shown to be effective in future tests, has potential to significantly increase the Browns Range mineral resource estimate.”
Along with feeding into the resource, results could also have an impact on NTU’s feasibility study.
“Being able to test and operate the ore sorting circuit in conjunction with the pilot beneficiation plant is providing extremely valuable data that you just can’t get from small bench-scale tests and this will feed into our feasibility study for a potential commercial-scale heavy rare earth operation at Browns Range,” Tory said.
NTU has now conducted two test campaigns with the sorter, including 41 test runs processing 5,300 tonnes of ore from the ROM stockpiles largely coming from Wolverine ore, and five test runs on Banshee ore that was bulk sampled from a surface costean that provided 285 tonnes of Banshee ore.
Sorter exceeds expectations
NTU has found that is able to sort two size fractions simultaneously.
The sortable fraction (>10mm material) of Wolverine ore can be successfully sorted (90% TREO recovery in 50% of the mass) and when combined with non-sortable fines achieves a 45% grade increase to the mill and over 95% TREO recovery when feeding a 0.9% TREO ore.
The sorter will produce feed for the beneficiation plant, with 4,479 tonnes of Wolverine ore already processed through the ore sorter circuit to the end of August.
Processing of the Wolverine ore sorted material in the beneficiation plant has resulted in better recoveries in the magnetic separation plant and flotation plant compared to feeding unsorted ore.
At Banshee, initial sorting tests have shown that the highly oxidised surface material contains a large fines fraction and that the grade of the sortable fraction (ie >10mm) can be doubled recovering more than 60% of the TREO in 25% of the mass.
An additional bulk sample is being extracted from deeper in the costean and three diamond drill holes are being drilled for further test-work.
Bulk ore sorting test-work is a key input for the full-scale beneficiation for the ongoing plant feasibility study.
The study will leverage the substantial technical, operational and economic data from the R&D test-work at the pilot plant since 2018.