Cobra Keeps 91% of Wudinna Rare Earth Recovery With 40% Less Reagent

• Cobra Resources reported 24-hour desorption test results from the Australian Nuclear Science and Technology Organisation (ANSTO) on bulk composite samples from the Boland and Head prospects at the Wudinna Rare Earths Project in South Australia. 
• At Boland, 0.3 molar (M) ammonium sulfate (AMSUL) at pH 3 recovered 70% neodymium and praseodymium (NdPr) and 67% dysprosium and terbium (DyTb), against 77% NdPr and 74% DyTb at 0.5 M. 
• Acidified site groundwater with no added AMSUL recovered 51% NdPr, 46% DyTb, and 50% heavy rare earth elements (HREE) from the Boland composite. 
• At Head, 0.3 M AMSUL at pH 3 recovered 36% NdPr and 52% DyTb, against 40% NdPr and 57% DyTb at 0.5 M.
• Reducing AMSUL from 0.5 M to 0.0 M at pH 3 cut uranium recovery on the Boland composite from 29% to 5%. 
• Cobra is targeting a maiden mineral resource estimate shortly, followed by further updates from the Wudinna scoping study. 

Company Overview

Cobra Resources (LSE: COBR) is a South Australian critical minerals developer advancing assets across all stages of the pre-production pathway. In 2023, the company identified the Boland ionic rare earth discovery at its Wudinna Project in the Gawler Craton, described as Australia's only rare earth project suitable for in situ recovery (ISR) mining, a low-cost, low-disturbance method that removes the need for excavation. In 2025, it optioned the Manna Hill Copper Project in the Nackara Arc and sold its Wudinna Gold Assets to Barton Gold for up to A$15 million in cash and shares. 

Test Program & Samples 

The test program measured how much rare earth material could be extracted from the Wudinna mineralization as the strength of the leaching solution was reduced. The Australian Nuclear Science and Technology Organisation (ANSTO) ran 24-hour desorption tests, in which a solution is passed through a sample to release the rare earth elements (REE) bound to it, on bulk composite samples from the Boland and Head prospects. The composites were prepared from samples across 26 intervals from 24 drill holes. 

The program compared ammonium sulfate (AMSUL), the reagent used to release the rare earths, at 0.5 molar (M), 0.3 M, and, for Boland, 0.1 M, alongside acidified site groundwater containing no added AMSUL, across selected pH conditions. The industry standard concentration is 0.5 M. The tests used site-sourced saline groundwater as the base solution.

Reported recoveries were calculated from the analyzed strength of the leach solution, adjusted for dilution, and were compared with recoveries calculated from assays of the solid residue left behind. One test on the Boland composite, run at 0.5 M AMSUL and a target pH of 4, was excluded from reporting because the solution and residue results did not reconcile within acceptable limits. 

Boland Composite Results

The Boland composite held most of its recovery as the reagent dose fell. At 0.3 M AMSUL and pH 3, the composite returned 70% neodymium and praseodymium (NdPr), 67% dysprosium and terbium (DyTb), and 67% heavy rare earth elements (HREE). The 0.5 M baseline at the same pH returned 77% NdPr, 74% DyTb, and 72% HREE, so the 0.3 M case retained approximately 91%, 91%, and 93% of those recoveries while using 40% less AMSUL. 

At 0.1 M AMSUL, recoveries were 58% NdPr, 53% DyTb, and 56% HREE. Acidified site groundwater with no added AMSUL recovered 51% NdPr, 46% DyTb, and 50% HREE. Recovery from acidified groundwater without added AMSUL indicates that a portion of the ionically bound REE can be desorbed without an external AMSUL addition.

Managing Director of Cobra Resources, Rupert Verco, quantifies what the weaker lixiviant, the leaching solution, costs in recovery:  

"Results demonstrate that Wudinna recoveries can be managed across a range of lixiviant strengths. At Boland, magnet rare earth recoveries were only reduced by 9% with a 40% reduction in ammonium sulfate reagent when compared to the industry standard 0.5M, while acidified site groundwater with no added ammonium sulfate recovered around half of the key magnet and heavy rare earths. This operating flexibility matters because recovery cannot be assessed in isolation. Lower reagent concentrations may reduce cost, supply exposure, and the salinity load introduced to the aquifer. The Scoping Study will test those potential benefits against the associated change in recovery."  

The scale of the composites gives confidence that the response is representative of the mineralized material tested. 

Head Composite Results

The Head composite retained a similar share of its baseline recovery at the lower reagent concentration. At 0.3 M AMSUL and pH 3, Head recovered 36% NdPr, 52% DyTb, and 53% HREE, retaining approximately 90%, 91%, and 91% of the 0.5 M results of 40% NdPr, 57% DyTb, and 58% HREE.  

Acidified site groundwater with no added AMSUL recovered 23% NdPr, 33% DyTb, and 36% HREE from the Head composite. HREE and DyTb recoveries exceeded those of NdPr under every Head test condition. 

Effect of pH & Uranium Mobilization 

Both AMSUL concentration and pH influenced recovery in the tests, and the two can be evaluated as operating trade-offs. On the Boland composite at 0.5 M AMSUL, recoveries rose as the solution became more acidic: 61% NdPr, 52% DyTb, and 53% HREE at pH 3.5, 77% NdPr, 74% DyTb, and 72% HREE at pH 3, and 83% NdPr, 80% DyTb, and 79% HREE at pH 2.5. On the Head composite at 0.5 M, recoveries moved from 23% NdPr, 28% DyTb, and 31% HREE at pH 4 to 40% NdPr, 57% DyTb, and 58% HREE at pH 3.

Lower reagent concentrations also reduced the amount of uranium drawn into solution. At pH 3, reducing AMSUL from 0.5 M to 0.0 M on the Boland composite reduced uranium recovery from 29% to 5%. 

Potential Benefits Under Assessment 

The lower-reagent operating cases will be assessed for three potential benefits: lower AMSUL consumption and reagent cost, reduced exposure to AMSUL supply and pricing, and lower additions of ammonium and sulfate to the confined aquifer. The Wudinna mineralization occurs within permeable sand in a hypersaline aquifer confined by low-permeability clay units. ISR circulates a mildly acidic sulfate solution through it via injection and extraction wells, with the confining geology intended to control solution flow between the wells.

These tests do not establish commercial reagent consumption or the preferred operating condition. Those conclusions require further column work, solution-management assessment, and economic evaluation during the scoping study.

Next Steps 

Cobra is targeting a maiden mineral resource estimate for Wudinna shortly, with further scoping study updates to follow. 

Cobra's ongoing test work is evaluating the technical and economic potential for ISR-based REE recovery at Wudinna. Engineering design, further test work, and the scoping study will determine the potential operating configuration, recovery assumptions, and development economics.

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