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Highlights:

  • AR3 achieves over 60% magnet rare earth recoveries in 3-tonne bulk leach campaign.
  • The company completes large-scale test to inform Koppamurra Pre-Feasibility Study.
  • AR3 identifies further optimisation potential in tail solution reprocessing and reagent use.

Australian Rare Earths Limited (ASX:AR3) has released an update on its metallurgical testwork program for the Koppamurra rare earths project located in South Australia, confirming recoveries exceeding 60% of magnet rare earth elements from a large-scale heap leach trial. The test, which processed approximately three tonnes of ore, was carried out to evaluate scalability and improve the project’s process design ahead of its Pre-Feasibility Study (PFS) expected in 2025.

The bulk heap leach trial was conducted at Brisbane Met Labs (BML) and followed earlier small-scale column testing at the Australian Nuclear Science and Technology Organisation (ANSTO). According to the company, the bulk leach results align with previous column leach findings and reinforce the potential to move forward with a progressive heap leach method.

The recent test campaign used blended samples collected from AR3’s 2022 Bulk Sample Pit operations. These samples had a total rare earth oxide (TREO) grade of 1393 ppm, including approximately 27% magnet rare earth elements—mainly Neodymium (Nd), Praseodymium (Pr), Dysprosium (Dy), and Terbium (Tb).

Three one-tonne testing containers, or “cribs,” were filled with agglomerated ore treated with sulphuric acid at a rate of 39 kg per tonne. A magnesium sulphate-based irrigation solution at pH 2.2 was applied over a period of 33 days, with fluid samples collected every 12 hours to monitor rare earth extraction performance.

Key operating parameters for the test included an irrigation rate of 5 litres per square metre per hour and the use of low-strength acid leachate. The leach cycle was intentionally extended beyond expected commercial durations to examine operational limits, including dripper spacing and flow efficiency.

The larger-scale test builds on earlier column leach trials, including test “C11,” also conducted at ANSTO, which used the same ore and process flow. Both tests demonstrated consistent recoveries, validating the scalability of the approach from lab-scale to bulk processing.

AR3 reported that the test results confirmed the ore’s suitability for agglomeration and heap leaching, noting its consistent physical characteristics. The company is continuing to investigate potential improvements to recovery rates, including the reprocessing of lower-grade leachate or “tail” solution, which may yield additional rare earths.

In parallel with the recovery tests, AR3 is running additional workstreams aimed at optimising reagent use, improving water recycling processes, removing impurities, and refining the rare earth precipitation stage. These efforts are part of a broader strategy to enhance overall process efficiency while reducing environmental impact.

This testwork phase is partially funded under the Australian Government’s International Partnerships in Critical Minerals Program, which allocated an AUD 5 million grant to support initiatives such as Koppamurra. The program is intended to help position Australia as a secure supplier of critical minerals globally, especially in response to emerging trade risks and export restrictions.

AR3 has emphasised the strategic context of its project, noting the increasing global demand for magnet rare earths and the risks associated with supply concentration in specific countries. The company believes that ionic clay-hosted rare earths deposits like Koppamurra may help diversify the international rare earth supply chain.

The data gathered from this bulk test will be used to inform engineering and operational decisions for the upcoming Pre-Feasibility Study, which remains on track for release in 2025.