Mount Ridley's Selectro Test 3 lifts scandium recovery to 91.8%

Mount Ridley Mines (ASX: MRD) has reported the final leach test in the initial program for its wholly owned, patent-pending Selectro™ process. In an ASX announcement dated 17 September 2026, the company said Test 3 delivered a substantial improvement in scandium recovery from unbeneficiated Grass Patch material, while using approximately half the reagent dose applied in the first two tests.

For retail investors, the important detail is not only the headline recovery figure, but also the conditions behind it and the work still required before the process can be assessed at a larger scale. The latest result is encouraging in some areas, but the response differed between elements and commercial operating costs have not yet been established.

On the same eight-sample composite used in the earlier Selectro tests, Test 3 achieved 91.8% scandium recovery, up from 80.0% in Test 2. The composite was drawn from five historical drill holes and was tested without prior beneficiation or process optimisation.

The lower reagent requirement is a central part of the result. Mount Ridley said Test 3 used approximately half the reagent dose applied in Tests 1 and 2. The company says this could reduce costs, although the available announcement does not disclose the detailed reagent chemistry or concentrations. It also makes clear that commercial operating costs have not yet been established.

The test was conducted by Nagrom as laboratory-scale work at atmospheric pressure. That matters because the result represents performance under an early test program rather than a demonstrated operating process. The material was unbeneficiated, and no process optimisation had been completed before the test.

The scandium result was accompanied by stronger recoveries for the rare earth categories described in the announcement. Heavy rare earth element recoveries reached up to 86%, with an average of approximately 84%, compared with a 78.5% average in Test 2. Light rare earth recoveries reached up to 81%, averaging approximately 77%, compared with 72.5% in Test 2.

The outcome for gallium moved in the opposite direction. Gallium recovery declined to approximately 41.5% from 55.8% in Test 2. Mount Ridley said this illustrates that different elements respond differently to the leach conditions.

That uneven profile is important when assessing what Test 3 has demonstrated. The process produced higher scandium and rare earth recoveries in this test, but it did not improve every targeted element at the same time. Further optimisation will therefore need to consider the balance between the elements rather than focusing on scandium recovery alone.

Mount Ridley plans further reagent optimisation, including work on the balance between scandium, rare earth and gallium recovery. This indicates that the company is still refining the process conditions and has not yet settled on a final operating approach.

Flotation testwork is underway to inform beneficiation before bulk-sample testing. Beneficiation could change the feed characteristics presented to the Selectro process, so the results from the current unbeneficiated composite should not be treated as the final recovery profile for a larger test program.

The company also plans to test Selectro on third-party feed. That work could provide information on how the process responds beyond the Grass Patch composite used in the initial program, but it is still a planned next step rather than a result reported in the announcement.

The announcement describes the current findings as early laboratory results. They are not demonstrated pilot-scale recoveries, and the company has not produced a saleable product from this work. For now, the evidence supports a promising laboratory outcome for scandium and several rare earth categories, alongside a lower reagent dose, while leaving reagent economics, process optimisation, beneficiation and scale-up to be tested.