Kula Gold’s (ASX: KGD) share price jumped 40 per cent today after its Rankin Dome project’s earn-in partner Australian Critical Minerals (ASX: ACM) revealed leach results that include rare earths head grades of up to 1674ppm total rare earth oxides (TREO).
ACM’s metallurgical laboratory leach tests on drill samples from the Rankin Dome project near the historic Western Australian town of Southern Cross also showed the more valuable magnetic rare earths oxides comprise 23 per cent of the TREO.
The testwork by ANSTO (the Australian Nuclear Science and Technology Organisation) involved the preliminary leachability testing of selected Rankin Dome reverse-circulation (RC) drill samples for their rare earths content. A total of 18 drill samples were used to prepare seven head samples, made up of four composites and three individual samples, to produce an 80g sub-sample for leach testing.
Sample head grade analyses ranged between 1148ppm and 1674ppm TREO, with oxides of the magnetic rare earth oxides praseodymium, neodymium, dysprosium and terbium determined to make up between 21 and 23 per cent of the TREO.
The magnetic rare earths component is not only valuable for its application in electric motors and the high-efficiency electricity generators that are now in high demand, but it is also more easily parted from its non-magnetic rare earths by magnetic separation methods.
Management says the samples were subjected to desorption tests by applying ammonium sulphate at a pH of 4 to mimic the conventional extraction methods used in overseas commercial ionic clay-hosted deposits. A second test employed an acid leach using 25 grams per litre strength hydrochloric acid.
Interestingly, ammonium sulphate desorption yielded low recoveries with a top value of only 1.6 per cent, while the 25g/l hydrochloric acid performed better, producing between 10.7 per cent and 30.8 per cent in five of the seven samples.
The outcome suggests that a refractory form of the mineralisation or its clay host may be inhibiting the desired levels of recovery and that further testwork may be required to fully understand the issues at play.
These could be considerations of laboratory processes alone, such as reagent selection or concentration, or may be geologically or weathering-related and / or about lateral or vertical variability in the local ground profile.
It is clear that rare earths mineralisation is present and can run at significant grades. The testwork to date has been only of a preliminary nature and further work will be pursued to resolve the source of the refractory influence at Rankin Dome.
As part of a 2022 deal, ACM agreed to spend $200,000 to complete 2000m of RC drilling within two years to earn up to a 51 per cent interest in the Rankin Dome project.
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