Cobra Keeps 91% of Boland Magnet Rare Earth Recovery at 40% Weaker Reagent

• At Boland, cutting ammonium sulfate strength by 40% kept about 91% of the neodymium-praseodymium and dysprosium-terbium recovery achieved at the standard strength.
• Acidified site groundwater with no added ammonium sulfate recovered 51% of the neodymium-praseodymium at Boland.
• Head returned 36% neodymium-praseodymium and 52% dysprosium-terbium recovery at the lower strength, about 90% of its standard-strength neodymium-praseodymium result.
• Uranium recovery at Boland fell from 29% to 5% when ammonium sulfate was removed from the solution at pH 3.
• Recovery, reagent use, solution chemistry, and economics will be assessed together in 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. Its portfolio also includes the Deloraine rare earth project in northern Tasmania.

What the Wudinna Desorption Tests Measured

The Australian Nuclear Science and Technology Organization completed 24-hour desorption tests, which measure how much rare earth material washes off the host clays into solution, on bulk composite samples from the Boland and Head prospects at the Wudinna Rare Earths Project. The composites were prepared from samples across 26 intervals taken from 24 drill holes. 

The program compared recoveries across a range of ammonium sulfate concentrations and pH conditions, pH being the measure of how acidic the solution is. Ammonium sulfate is the reagent in the lixiviant, the leaching solution circulated through the mineralized sands, and every test used saline groundwater sourced from the site. Strengths of 0.5 molar, the industry standard, and 0.3 molar were tested at both prospects, with 0.1 molar added at Boland, alongside acidified groundwater carrying no added ammonium sulfate.

Reported recoveries are calculated from analyzed liquor concentrations adjusted for dilution and were compared with recoveries calculated from residue assays. One Boland test, run at 0.5 molar and a target pH of 4, was excluded from reporting because the liquor and residue assays did not reconcile within acceptable limits.

Boland Recoveries Across Reagent Strengths

At pH 3, the 0.3 molar solution recovered 70% of the neodymium-praseodymium, 67% of the dysprosium-terbium, and 67% of the heavy rare earth elements (HREE). Those figures retained approximately 91%, 91%, and 93% of the recoveries achieved at 0.5 molar, which were 77%, 74%, and 72%, while using a 40% lower ammonium sulfate concentration.

At 0.1 molar, recoveries held at 58% for neodymium-praseodymium, 53% for dysprosium-terbium, and 56% for HREE. Acidified groundwater with no added ammonium sulfate recovered 51%, 46%, and 50% of the same groups, which indicates that a portion of the ionically bound rare earths can be desorbed without any external reagent addition.

Managing Director of Cobra, Rupert Verco, quantifies the recovery given up at Boland for the reduction in reagent:

"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 sulphate reagent when compared to the industry standard 0.5M, while acidified site groundwater with no added ammonium sulphate recovered around half of the key magnet and heavy rare earths."

Acidity moved recovery as well. At 0.5 molar, lowering the pH from 3.5 to 2.5 raised Boland neodymium-praseodymium recovery from 61% to 83%.

Head Prospect Results

Head returned lower neodymium-praseodymium recoveries than Boland, but a consistent response to reagent strength. At pH 3, the 0.3 molar solution recovered 36% of the neodymium-praseodymium, 52% of the dysprosium-terbium, and 53% of the HREE, retaining approximately 90%, 91%, and 91% of the 0.5 molar results of 40%, 57%, and 58%.

Acidified groundwater with no added ammonium sulfate recovered 23% of the neodymium-praseodymium, 33% of the dysprosium-terbium, and 36% of the HREE. Heavy rare earth and dysprosium-terbium recoveries exceeded neodymium-praseodymium recovery under every Head test condition.

Lower Uranium Mobilization & Reagent Trade-Offs

At pH 3 on the Boland composite, reducing the ammonium sulfate concentration from 0.5 molar to 0.0 molar cut uranium recovery from 29% to 5%. Less uranium entering the solution alongside the rare earths is one of the effects that the lower-reagent cases will be assessed for.

The company will also assess those cases for lower ammonium sulfate consumption and reagent cost, reduced exposure to ammonium sulfate supply and pricing, and smaller additions of ammonium and sulfate to the confined aquifer, which would further reduce environmental impacts.

Verco sets the recovery figures against those potential savings:

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

Next Steps

The results define a range of potential operating conditions for further engineering trade-off studies. They will inform the Wudinna scoping study's assessment of recovery, reagent consumption, solution chemistry, and project economics, which will be weighed together to define preferred commercial operating parameters.

Verco connects the scale of the samples to the next round of work:

"The scale of the composites provides confidence that the response is representative of the mineralised material tested, and the consistent performance at both Boland and Head supports the next phase of optimisation. We expect to announce the maiden Mineral Resource Estimate shortly, followed by further updates from the Scoping Study."

The maiden resource estimate and the scoping study updates are the next Wudinna disclosures.

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