Cobra Resources plc (LSE: COBR), which is advancing the Wudinna Rare Earth and Manna Hill Copper projects in South Australia, has published diagnostic leach test results from 42 drill return samples sent to the Australian Nuclear Science and Technology Organisation (ANSTO). The results show rare earth recoveries of up to 88.4% total rare earth plus yttrium (TREY) from the Pidinga formation at the Boland Mineral Resource area. Notably, the Narlaby formation at the Head Mineral Resource area returned up to 88% TREY, prompting the company to study whether this material could be reclassified into the in situ recovery (ISR) portion of the Head Mineral Resource Estimate.

Key Points

  • Cobra Resources plc (LSE: COBR) is an LSE-listed critical minerals developer focused on South Australia
  • ANSTO diagnostic leach tests on 42 samples from Boland and Head returned up to 88.4% TREY recovery from the Pidinga formation
  • All three Narlaby formation samples at Head achieved up to 88% TREY, 93% dysprosium plus terbium, and 88% samarium — though ISR amenability has not yet been established
  • Investors should watch for Narlaby formation reclassification progress, large-scale ISR column results, and scoping study updates

ANSTO Leach Tests Deliver Up to 88.4% TREY from Boland's Pidinga Formation

The 42 samples were subjected to a 24-hour ambient temperature leach targeting a pH of 3 using a 0.5 molar ammonium sulphate lixiviant solution. At the Boland Mineral Resource area, Pidinga formation results reached up to 88% TREY, 87% neodymium plus praseodymium, 73% dysprosium plus terbium, 81% samarium, and 76% yttrium. At the Head Mineral Resource area, Pidinga formation recoveries were comparatively lower, reaching up to 66% TREY and 62% neodymium plus praseodymium. Managing Director Rupert Verco noted in the announcement that one Pidinga sample delivered 88.4% TREY extraction, including 81.2% samarium and 75.6% yttrium, alongside strong magnet rare earth extraction.

Narlaby Formation at Head Delivers Exceptional Results, ISR Amenability Under Evaluation

The three Narlaby formation samples from the Head discovery area produced the strongest recoveries in the dataset, achieving up to 88% TREY, 88% neodymium plus praseodymium, 93% dysprosium plus terbium, 88% samarium, and 84% yttrium. The announcement states that the Narlaby formation is both permeable and mineralised but has not yet been demonstrated to be amenable to ISR for Mineral Resource Estimate purposes. Cobra has stated it will study the formation in greater detail with the objective of establishing its whole or partial inclusion in the ISR portion of the Head MRE, which the company describes as a compelling opportunity to convert existing open-pit classified mineralisation into ISR recoverable resources.

Wudinna ISR Strategy Targets Bottom-Quartile Costs and Western World First

Cobra holds a maiden JORC-compliant Mineral Resource Estimate of 150 million tonnes grading 470 parts per million total rare earth oxides at Wudinna. The company's development strategy centres on confined-aquifer ISR, a technique with established precedents in South Australian uranium production, which the company believes could position Wudinna as the Western World's first rare earths ISR operation. The announcement emphasises that commercial recoveries, costs, and environmental performance remain subject to integrated testing, field validation, and engineering studies — a material consideration for investors assessing project advancement risk at this early development stage.

Next Steps Include Large-Scale ISR Column Study and Metallurgical Domain Definition

Cobra has outlined three immediate workstreams: operating a large-scale ISR column to replicate a proposed small-scale production study for crude precipitation, transport, and re-dissolution; defining metallurgical domains and assessing the relationship between extraction, mineralogy, and aquifer permeability; and conducting trade-off sensitivity evaluations to optimise economics through recovery and reagent analysis. The results will be assessed alongside permeability, intact-core testing, and field performance data, aimed at delivering confidence in scoping study estimates. The company also holds a significant shareholding in Barton Gold (ASX: BDG), following the 2025 sale of non-core gold assets for A$15 million in cash and shares.