Mount Ridley raises scandium recovery with half-dose Selectro test

Half-dose test sets new scandium recovery record

Mount Ridley Mines Limited (ASX:MRD) has produced its strongest Selectro™ result yet, lifting scandium recovery to 91.8% while using approximately half the reagent applied in its first two tests. Average heavy rare earth element recovery rose to 84.0%, from 78.5% in Test 2, while average light rare earth recovery increased to about 77%, from 72.5%.

The result came from the same unbeneficiated Grass Patch composite used in earlier work, with no process optimisation applied. That makes the outcome notable as an early laboratory signal, but it also limits what can be said about repeatability or commercial performance.

Scandium and rare earths improve together

Selectro™ Test 3 recorded maximum HREE recovery of 86% and maximum LREE recovery of 81%. Individual results included 86.3% recovery for yttrium, 86.2% for holmium, 85.3% for gadolinium and 85.0% for dysprosium, while neodymium recovery reached 81.7%.

Mount Ridley attributes the shift to molecular tuning of the leaching chemistry, allowing the process to target different metals. The company has not yet established the lowest workable reagent concentration, leaving open the possibility of further dose reduction, although the filing does not quantify the resulting economics.

Gallium recovery exposes the trade-off

The test was not uniformly better across all metals. Gallium recovery fell to approximately 41.5%, from 55.8% in Test 2, despite remaining well above the zero recovery recorded in the hydrochloric acid baseline. Mount Ridley says the result shows that individual elements respond differently to reagent concentration and expects gallium performance may improve through further tuning and beneficiation.

That trade-off is central to the next phase of work. A process that improves scandium and rare earth recovery at lower reagent intensity still needs to balance those gains against gallium recovery and the broader value of the mineral suite.

Flotation will test the beneficiation case

Flotation testwork is now underway ahead of bulk sample testing. Mount Ridley says earlier automated mineralogy work found the rare earths predominantly hosted in discrete phosphate minerals including xenotime, crandallite-group phosphates and monazite/rhabdophane. The company expects those findings to inform a beneficiation step before the Selectro™ process is tested on larger and flotation-treated material.

The reported results came from laboratory testing by Nagrom using approximately 90-gram aliquots from a 16.8-kilogram composite prepared from five historical drill holes. The tests were conducted at atmospheric pressure, and Selectro™ achieved maximum recoveries in under four hours, compared with a 24-hour leach period for the hydrochloric acid baseline. Reagent chemistry and concentrations remain undisclosed.

Process economics remain unproven

Mount Ridley says the lower dose could reduce reagent consumption and the volume requiring recycling in its closed-loop process. Those are potential cost advantages rather than established project economics: the work remains small-scale, uses unbeneficiated material and has not yet demonstrated performance through bulk or pilot testing.

The next milestones are updated process economics, lower-dose optimisation, completion of flotation work, bulk sample testing and validation on third-party feed. The key test will be whether the half-dose performance survives a larger, beneficiated sample without sacrificing gallium recovery or the rare earth gains.