Western Mines Group has reported a 7.2 million-tonne contained nickel resource at its Mulga Tank project in Western Australia’s Eastern Goldfields, which the company says is the largest nickel sulphide resource of its kind in Australia.
The updated JORC-compliant estimate covers 2.647 billion tonnes grading 0.27 per cent nickel, with 131 parts per million of cobalt, 77 parts per million of copper and 19 parts per billion of combined platinum and palladium. It is based on a 0.20 per cent nickel cut-off grade.
Mulga Tank is in the Minigwal Greenstone Belt, about 190km north-east of Kalgoorlie. The deposit also contains an estimated 347,000 tonnes of cobalt, 205,000 tonnes of copper and 1.6 million ounces of combined platinum group elements.
The scale of the Mulga Tank nickel resource has increased substantially since the company’s previous estimate in April 2025, which contained 5.3 million tonnes of nickel within 1.968 billion tonnes of material at an average grade of 0.27 per cent nickel.
Mulga Tank nickel resource expanded through drilling
The latest estimate incorporates results from 32 additional reverse circulation and diamond drill holes completed over the past 18 months.
Total tonnes have risen by more than 35 per cent, while the higher-confidence indicated category has increased by 98 per cent. The indicated resource now stands at 1.121 billion tonnes grading 0.28 per cent nickel, equivalent to 3.1 million tonnes of contained nickel.
The remaining 1.526 billion tonnes is classified as inferred material, grading 0.27 per cent nickel for a further 4.1 million tonnes of contained metal.
Western Mines said the deposit’s current estimate covered only the shallow, disseminated nickel mineralisation identified by drilling so far. Mineralisation begins at an average depth of about 65 metres and extends to approximately 460 metres below the surface.
The company believes the geometry and shallow nature of the deposit could support a large-scale open-pit mining operation, although the project remains at an early stage and its economic potential has yet to be assessed through the planned scoping study.
The resource remains open in several directions, offering scope for further expansion. Mulga Tank is hosted within a large ultramafic complex and has been compared with major nickel deposits in the Yilgarn Craton, including BHP’s Mt Keith and Yakabindie operations.
Deeper drilling points to higher-grade nickel sulphides
Drilling has also identified potential for richer, massive nickel sulphide mineralisation near the base of the ultramafic intrusion.
One deep reverse circulation hole returned 116 metres grading 0.5 per cent nickel from a depth of 1,303 metres. A diamond tail from the same hole produced a 38-metre intercept grading 0.71 per cent nickel from 1,324 metres.
The hole also encountered a one-metre section of individual sulphide segregation grading 2.34 per cent nickel. Across the wider system, it returned 694 metres grading 0.31 per cent nickel from 120 metres.
Those deeper results sit beneath the shallow disseminated resource and point to a separate zone of potentially higher-grade mineralisation. Further drilling would be required to establish its scale and significance.
Scoping study to assess development potential
Western Mines is now progressing its first scoping study for Mulga Tank, using other large, low-grade nickel sulphide deposits as benchmarks for potential operating costs and development parameters.
Initial metallurgical testing indicates that nickel sulphides from the disseminated material can be recovered using conventional flotation, with recovery rates of between 40 and 45 per cent. The early results were based on rougher flotation tests and conservative assumptions benchmarked against large, low-grade Canadian nickel sulphide projects.
The company said further metallurgical work could assess additional conventional processing optimisation options as the project advances.
At 7.2 million tonnes of contained nickel, Mulga Tank is reported to exceed the publicly stated contained nickel inventories of Australian peers by up to 3.4 times. For comparison, the raw resource figures cited by Western Mines put Yakabindie at about 2.1 million tonnes of nickel and Mt Keith at roughly 1.2 million tonnes.
The forthcoming scoping study is expected to provide the first assessment of the potential economics of developing the large-scale Western Australian deposit.
