Mount Ridley Mines Achieves 91.8% Scandium Recovery at Half Reagent Dose
Key Takeaways
- Selectro™ Test 3 achieved 91.8% scandium recovery, up from 80.0% in Test 2, while using approximately half the reagent dose — a simultaneous improvement in both recovery and cost efficiency.
- Heavy rare earth element (HREE) recovery averaged 84.0% in Test 3 (up from 78.5%), and light rare earth element (LREE) recovery averaged 77% (up from 72.5%), with standout individual recoveries including Yttrium at 86.3% and Dysprosium at 85.0%.
- The Selectro™ process operates at low temperature and ambient pressure with a closed-loop reagent recycling design, and the company has not yet established the lower limit of reagent concentration — meaning further cost and recovery improvements remain possible.
- All testwork to date has been conducted on unbeneficiated, non-optimised feed, meaning the results represent a baseline from which the upcoming flotation and bulk sample programme is specifically designed to improve.
- TIMA mineralogy results confirmed rare earths are predominantly hosted in discrete phosphate minerals including xenotime and monazite, supporting strong flotation potential as the programme advances.
Selectro™ Test 3 delivers record scandium and rare earth recoveries at half the reagent dose
Mount Ridley Mines (ASX: MRD) has announced that Selectro™ Test 3 achieved a scandium recovery of 91.8% (up from 80.0% in Test 2), heavy rare earth element (HREE) recovery averaging 84.0% (up from 78.5%), and light rare earth element (LREE) recovery averaging 77% (up from 72.5%). Critically, these gains were achieved at approximately half the reagent dose used in Tests 1 and 2, making this a genuine “more with less” result. Selectro™ is Mount Ridley’s wholly-owned and patent-pending leach process.
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What the Selectro™ results show
Test 3 by the numbers
The improvement stands out because the same unbeneficiated Grass Patch 8-sample composite was used across all tests, with no process optimisation applied. That means the recovery gains in Test 3 are attributable to reagent and molecular tuning alone, not to changes in feed material or process conditions.
The table below sets out the full comparative elemental breakdown from Table 2 of the source announcement, showing recovery percentages across the HCl baseline, Selectro™ Test 1, Test 2, and Test 3.
| Grouping | Element | HCl Baseline (%) | Selectro™ Test 1 (%) | Selectro™ Test 2 (%) | Selectro™ Test 3 (%) |
|---|---|---|---|---|---|
| LREE | Nd | 30.2% | 55.2% | 75.2% | 81.7% |
| LREE | Pr | 30.8% | 48.9% | 73.6% | 81.3% |
| LREE | La | 28.9% | 50.2% | 71.3% | 75.9% |
| LREE | Ce | 35.5% | 52.1% | 69.9% | 75.7% |
| LREE | Sm | 36.0% | 51.1% | 72.7% | 80.4% |
| HREE | Dy | 39.4% | 54.4% | 77.3% | 85.0% |
| HREE | Tb | 45.7% | 62.6% | 83.1% | 83.1% |
| HREE | Y | 46.8% | 61.1% | 80.2% | 86.3% |
| HREE | Er | 49.1% | 60.2% | 77.6% | 83.2% |
| HREE | Eu | 0.0% | 49.4% | 76.7% | 78.7% |
| HREE | Gd | 45.8% | 54.4% | 77.5% | 85.3% |
| HREE | Ho | 51.1% | 58.6% | 77.4% | 86.2% |
| Scandium | Sc | 27.6% | 62.1% | 80.0% | 91.8% |
| Gallium | Ga | 0.0% | 57.3% | 55.8% | 41.5% |
Standout individual element recoveries in Test 3 include:
- Y (Yttrium) at 86.3%
- Ho (Holmium) at 86.2%
- Gd (Gadolinium) at 85.3%
- Dy (Dysprosium) at 85.0%
- Sc (Scandium) at 91.8%
Gallium recovery came in at 41.5% in Test 3, down from 55.8% in Test 2 at the reduced reagent dose. The company notes this is a sign that individual elements respond differently to reagent concentration and believes recovery can be improved through beneficiation and optimisation.
Molecular tuning — what drove the improvement
The Selectro™ leaching chemistry can be adjusted at the molecular level to target specific metals. In Test 3, the leaching was tuned to improve scandium recovery, which is what drove the jump from 80.0% to 91.8%, while HREE recoveries also lifted across the board. Importantly, the company has not yet established the lower limit of reagent concentration for the Selectro™ Process, which means further upside in both recovery and cost efficiency may be achievable at an even lower dose. The process operates at low temperature and ambient pressure and is designed to fully recycle its reagents.
Chris Larder, Chief Technology Officer
“The latest test of the Selectro™ program looked at whether we could improve metal recovery through molecular tuning of the leaching regime. The results make it clear that tuning delivered material improvement, with scandium recovery increasing from 80% to 91.8% while the reagent dose was halved. Being able to manage the process to get outcomes like that is genuinely exciting.
Selectro™ also operates at low temperature and ambient pressure and is designed to fully recycle its reagents, which together point to a potentially very attractive operating cost profile compared with alternative extraction methods.”
Why reagent efficiency matters for project economics
A leach process works by dissolving target metals from ore so they can be separated and recovered. In hydrometallurgy (the use of aqueous chemistry to extract metals), reagent costs are a significant operating cost driver. Using less reagent per tonne of ore while simultaneously recovering more metal directly improves projected margins.
Selectro™ is already designed on a closed-loop basis, meaning reagents are recycled rather than consumed on a single pass. Test 3 now shows the dose itself can be halved while improving recovery, pointing to a structurally lower cost profile compared with the industry-standard HCl leach. The testwork was conducted by Nagrom Pty Ltd at its Kelmscott, WA laboratory.
CEO Allister Caird
“… 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. …”
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What comes next for the Selectro™ program
The company has outlined a clear set of next steps for the Selectro™ programme:
- Incorporate Test 3 results into updated process economics and scoping assumptions
- Conduct further testwork to establish the lower limit of reagent concentration and optimise recovery balance across scandium, REEs and gallium
- Complete flotation testwork to inform the beneficiation approach for the bulk sample programme
- Conduct bulk sample testwork on both the reduced-reagent feed validated in Test 3 and the flotation-beneficiated feed
- Validate the Selectro™ Process on third-party feed
The mineralogy supports confidence in the flotation step. TIMA 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/rhabdophane, which points to strong flotation potential.
On scale, the CEO’s comments reference the world’s largest scandium resource at Grass Patch. The Grass Patch Project is located approximately 25 kilometres north of Esperance in Western Australia.
The processing gains in Test 3 sit against a resource backdrop that is itself still expanding, with high-grade scandium beyond Grass Patch confirmed in recent drilling that extended mineralisation outside the current resource boundary.
Test 3 results are a foundation, not a ceiling. The programme now advances to flotation and bulk sample testing with a validated reagent-efficient approach and a wholly-owned and patent-pending process the company owns outright. The unbeneficiated, non-optimised basis of all testwork to date means the results achieved so far represent a starting point from which the optimisation programme is specifically designed to improve.
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