Mount Ridley Mines (ASX:MRD) records 91.8% scandium recovery in Selectro Test 3

Mount Ridley Mines has reported results from the final leach test in the current round of its Selectro process metallurgical testwork program.

The testing was conducted on unbeneficiated material from the Grass Patch Project without process optimisation.

Highlights

Selectro is Mount Ridley’s wholly owned and patent pending leach process, with Test 3 designed to assess the effect of a reduced reagent dose on recovery performance using the same Grass Patch composite tested in the program reported on 12 August 2026.

The improvement in scandium and rare earth recovery reflected molecular tuning of the Selectro leaching chemistry, under which the composition of the leaching molecule can be adjusted to optimise recovery of targeted metals.

Test 3 was tuned to improve scandium recovery, which increased from 80.0% in Test 2 to 91.8%.

Average heavy rare earth element recovery increased from 78.5% in Test 2 to 84.0% in Test 3, while average light rare earth element recovery increased from 72.5% to 77%.

Individual results included yttrium recovery of 86.3%, holmium recovery of 86.2%, gadolinium recovery of 85.3% and dysprosium recovery of 85.0%.

Gallium recovery declined from 55.8% in Test 2 to approximately 41.5% under the reduced reagent conditions, remaining above the 0.0% recovery recorded in the hydrochloric acid baseline test.

The company said individual elements responded differently to reagent concentration and expects the gallium result may be improved through beneficiation and optimisation processes.

The metallurgical work was undertaken by Nagrom at its Kelmscott laboratory in Western Australia.

Representative dry weight aliquots of approximately 90 g were taken from a 16.8 kg homogenised composite prepared from 5 historical Grass Patch diamond drill holes.

The hydrochloric acid baseline and Selectro tests were conducted over a 24 hour leach period at atmospheric pressure, with the Selectro tests achieving maximum recoveries in under 4 hours.

Detailed information concerning the Selectro reagent chemistry, concentrations and additions remains proprietary and was not disclosed.

Mount Ridley Managing Director and CEO Allister Caird said further work would examine the reagent settings and recovery response of individual minerals.

“We haven't yet established where the reagent concentration breaks for the process, providing further opportunity to optimise the reagent dose and recovery of targeted individual minerals.”

Selectro is designed on a closed loop basis with reagents intended to be recycled, and Mount Ridley said the reduced reagent dose, combined with higher rare earth and scandium recoveries, pointed to an opportunity to lower reagent costs and increase recycling efficiency as testwork advances towards bulk sample and pilot scale programs.

The Grass Patch Project is located approximately 25 km north of Esperance in Western Australia and hosts defined heavy rare earth element, scandium and gallium resources identified through 70,000 m of historical drilling.

Mineralogical results announced on 6 August 2026 confirmed that rare earths in the tested composite are predominantly hosted in discrete phosphate minerals, including xenotime, crandallite group phosphates and monazite or rhabdophane.

Flotation testwork is underway, with the results to inform the beneficiation approach for the bulk sample program.

Mount Ridley’s next steps include establishing the lower reagent concentration limit, optimising the balance between scandium, rare earth and gallium recovery, incorporating the Test 3 results into updated process economics and scoping assumptions, completing bulk sample testing and validating the Selectro process on third party feed.