Mount Ridley Mines has reported that initial metallurgical testing of its proprietary Selectro process achieved significantly higher recoveries of heavy rare earth elements (HREE), scandium, and gallium from material at its Grass Patch Complex in Western Australia. All three mineral categories are classified as critical minerals by the Australian, United States, and European governments, reflecting their role in technologies such as permanent magnets for electric vehicles and wind turbines, aerospace alloys, and semiconductors.

The in-house developed leach process delivered materially higher recoveries than conventional hydrochloric acid (HCl) leaching on the same composite sample, providing early evidence that multiple critical minerals could potentially be recovered through a single processing circuit. Most rare earth projects globally target either light or heavy rare earths; co-recovery of HREE alongside scandium and gallium from a single leach circuit would be unusual and could differentiate the project if results are replicated at larger scale.

Independent Perth-based metallurgical laboratory Nagrom conducted the testwork using historical drill samples from the Grass Patch Complex.

For heavy rare earth elements, the Selectro process achieved recoveries ranging from 77% to 83% across dysprosium, terbium, yttrium, erbium, europium, gadolinium, and holmium. Dysprosium and terbium are among the highest-value rare earths due to their use in heat-resistant permanent magnets. The process also delivered an 80% recovery rate for scandium, compared to approximately 25% achieved using HCl leaching on the same sample. Mount Ridley stated that further work will focus on improving scandium recovery through reagent and process optimisation.

Gallium showed another notable difference between the two methods. Selectro achieved an average gallium recovery of 56%, while the HCl baseline recovered no gallium in the comparative testing. Gallium is a by-product of bauxite and zinc processing with no dedicated primary mine, and supply is concentrated among a small number of producers. The company noted that the ability to potentially recover gallium alongside rare earths and scandium through the same leach process could represent an additional commercial opportunity.

The next testing phase will involve evaluating Selectro on a bulk sample from Grass Patch. Following encouraging results from recent mineralogical analysis, Mount Ridley also plans to test beneficiated material, applying flotation to a portion of the bulk sample prior to leaching. Moving from historical drill samples to bulk-sample testwork is a standard step in demonstrating that laboratory recoveries can be sustained at larger volumes.

Additionally, the company intends to test the Selectro process on third-party feed to assess whether the technology could have applications beyond the Grass Patch deposit. Mount Ridley indicated that the process may have potential across a range of deposit types, including lateritic and sedimentary-hosted systems, and is evaluating potential third-party licensing opportunities on a global basis. Licensing the Selectro process to other operators would represent a different business model from standalone mine development and could position Mount Ridley as a technology provider within the critical minerals processing sector.