Mount Ridley Mines Limited has validated its heavy rare earth element resource through historical metallurgical testwork showing recoveries up to 86.5% across the Grass Patch Complex. The results underpin ongoing development efforts and metallurgical optimisation plans.
- Historical metallurgical testwork confirms heavy rare earth leach recoveries up to 86.5%
- Beneficiation tests demonstrate potential feed grade upgrades up to 202%
- Heavy rare earths leach more effectively than light rare earths at Mount Ridley
- Project includes significant scandium and gallium by-product potential
- Results support development of a multi-element critical minerals project in Western Australia
Historical Metallurgical Data Validates Heavy Rare Earth Resource
Mount Ridley Mines Limited (ASX:MRD) has reported that a comprehensive review of historical metallurgical testwork confirms strong heavy rare earth element (HREE) leach recoveries across its Grass Patch Complex in Western Australia. The testwork, which predates the company’s current focus on the Keith’s (Block 1) and Winston’s (Block 2) deposits, shows heavy rare earth recoveries reaching up to 86.5% under conventional hydrochloric acid leach conditions. These findings provide technical validation for the recently announced HREE Mineral Resource, which contains 41% heavy rare earth oxides (HREO), including critical elements such as dysprosium (Dy), terbium (Tb), and yttrium (Y).
The metallurgical results demonstrate that the Mount Ridley mineralisation is amenable to conventional hydrometallurgical processing techniques, offering a pathway for further development. Notably, heavy rare earths leach more effectively than light rare earths at the project, with consistent extraction performance observed across multiple prospects within the Grass Patch Complex, including Vincent, Jody, and Winston.
Beneficiation and Processing Potential
Beneficiation testwork conducted by Simulus Laboratories has shown promising results, with upgrade factors of up to 202% achieved by screening at 75 microns. This indicates a strong potential to significantly improve feed grades prior to leaching, enhancing the economic viability of the project. The beneficiation process effectively concentrates rare earth elements by removing barren material, with over 80% of total rare earth oxides (TREO) concentrated within approximately 50% of the sample mass.
Acid leach testing supervised by Independent Metallurgical Operations Pty Ltd (IMO) and conducted by Metallurgy Pty Ltd and the Australian Nuclear Science and Technology Organisation (ANSTO) confirmed that key heavy rare earth elements respond favourably to hydrochloric acid leaching. The highest heavy rare earth leach recoveries were recorded at the Winston’s prospect (Block 2), part of the current Mineral Resource. Additionally, magnetic rare earth elements such as neodymium (Nd) and praseodymium (Pr) showed strong recoveries, particularly at Vincent, where magnet rare earth element recoveries averaged 76.9% under optimal conditions.
Strategic Importance and Future Development
Mount Ridley Mines is advancing metallurgical optimisation programs to refine processing flowsheets and explore the potential recovery of scandium and gallium as by-products. These elements are present within the same regolith-hosted system and could provide additional economic upside. The company has initiated discussions with Australian and international research groups, including a collaboration with Lawrence Livermore National Laboratory, to develop optimised extraction and purification pathways tailored to the project’s clay-hosted critical mineralisation.
These metallurgical results complement the company’s recent resource announcements, including a significant inferred heavy rare earth resource of 122.56 million tonnes at 889 ppm TREO, rich in dysprosium and terbium, as detailed in the company’s March 2026 release. This foundation supports Mount Ridley’s objective to develop a multi-element critical minerals project capable of contributing to Australia’s and allied nations’ strategic supply chains for rare earths and associated critical metals.
Located approximately 55 kilometres northeast of Esperance, Western Australia, the Mount Ridley Project benefits from accessible infrastructure, including sealed roads and proximity to port facilities. The project’s geological setting within the Albany-Fraser Mobile Belt features mafic-dominated lithologies favourable for heavy rare earth mineralisation, distinguishing it from typical regolith-hosted rare earth systems.
Mount Ridley Mines’ Managing Director and CEO, Allister Caird, emphasised the relevance of the historical data, stating that the strong heavy rare earth leach response provides a solid technical foundation for the next phase of metallurgical work. This includes ongoing optimisation and collaboration with international partners to advance the project’s development.
Bottom Line?
While historical metallurgical results provide a strong technical base, further optimisation and pilot-scale testing will be critical to confirm the economic viability and scalability of processing pathways for Mount Ridley’s heavy rare earth and associated critical minerals.
Questions in the middle?
- How will upcoming metallurgical optimisation programs influence the project’s development timeline and capital requirements?
- What are the potential challenges in scaling up hydrometallurgical processing for clay-hosted heavy rare earth mineralisation at Mount Ridley?
- How might the integration of scandium and gallium recovery impact the overall project economics and market positioning?