Mount Ridley Mines Limited (ASX: MRD) has reported that a review of historical metallurgical test work confirms a highly encouraging heavy rare earth leach response across the Grass Patch Complex. Mount Ridley is focused on developing a multi-element critical minerals project. The company aims to contribute to the emerging Australian and allied supply chain for strategic metals.
The historical test work, predating the company’s current focus, was not originally designed to target heavy rare earth dominant mineralisation. However, the results are considered directly relevant, demonstrating consistent heavy rare earth leach response and providing confidence in the current heavy rare earth mineral resource estimate. The metallurgical program evaluated rare earth extraction using acid leaching test work on samples from several prospects across the Grass Patch Complex, including Vincent, Winstons, and Jody.
Key highlights from the historical metallurgical testwork include heavy rare earth recoveries of up to 86.5% achieved under conventional hydrochloric acid leach conditions. The current HREE Mineral Resource contains 41% HREO, including high-value heavy rare earths such as Dysprosium (Dy), Terbium (Tb), and Yttrium (Y). Metallurgical performance is strongest within the mafic-dominated lithological setting of the Grass Patch Complex, which differs from typical regolith-hosted REE systems. Light magnetic rare earth (NdPr) recoveries also reached up to 85.2%, with Vincent averaging 76.9% recovery under optimal conditions.
Allister Caird, Managing Director & CEO, stated that these historical metallurgical results clearly show a strong heavy rare earth response across the Grass Patch Complex, providing a solid technical foundation for further metallurgical work. Initial beneficiation testwork achieved upgrade factors of up to 202%, demonstrating the potential to significantly improve feed grade prior to leaching. The company plans to incorporate scandium and gallium into the broader heavy rare earth development program, with discussions underway with Australian and international research groups to design optimised extraction and purification pathways.
