Mount Ridley Mines says its patent-pending Selectro process recovered 91.9% of aluminium and 96.7% of iron from a third-party bauxite sample at below 100°C. The test produced a small, pH-neutral silica-rich residue instead of conventional red mud, but product purification, economics and scale-up remain unproven.
- 91.9% aluminium and 96.7% iron recovery from a Darling Range bauxite composite
- Test conducted below 100°C, beneath conventional Bayer digestion temperatures
- Small, pH-neutral silica-rich residue replaced conventional red mud in the test
- Results came from an approximately 1kg composite of selected third-party samples
- Demonstration plant design and further optimisation are planned
First bauxite test delivers high aluminium and iron extraction
Mount Ridley Mines Limited (ASX:MRD) has produced a strong first result outside its home turf, recovering 91.9% of aluminium and 96.7% of iron from bauxite supplied by Australian Silica Quartz Group (ASX:ASQ). The test marks the first application of Mount Ridley’s patent-pending Selectro process to bauxite and the first use of the chemistry on feedstock beyond the company’s Grass Patch Complex.
Australian Laboratory Services conducted the leach test on a composite made from 16 vacuum-drill samples taken across the Athena and Ceres prospects at ASQ’s Darling Range bauxite project in Western Australia. The recoveries represent metal extracted into solution, rather than confirmed saleable aluminium or iron products. Mount Ridley still has to demonstrate the separation and purification stages needed to turn that solution into products.
The result also comes with a meaningful sampling caveat. The composite weighed approximately 1 kilogram and was prepared from selected samples supplied by ASQ; Mount Ridley said it has not independently verified ASQ’s drilling, sampling or survey data, and the material is not intended to represent the Darling Range deposit as a whole.
Silica-rich residue offers an alternative to red mud
The more distinctive feature was what remained after leaching. The dried residue represented about 25% of the original feed mass and consisted predominantly of silica, with more than 90% of the silica staying in the residue. Mount Ridley described it as small, pH-neutral and silica-rich, contrasting it with the caustic, iron-bearing red mud produced by the conventional Bayer refining process.
Selectro operated below 100°C in this test. That is below the roughly 145°C to more than 250°C range cited by Mount Ridley for Bayer digestion, although the company has not yet provided an energy balance, reagent cost profile or process economics for a bauxite flowsheet. The Bayer process also involves later calcination above 1,000°C, so the test temperature alone does not establish the total energy or emissions performance of a commercial refinery.
The potential prize is substantial: Mount Ridley estimates the aluminium industry generates 150 million to 200 million tonnes of bauxite residue each year, with global stockpiles of about 4 billion tonnes. The company’s proposed alternative is still at an early stage, however. The chemistry has not been optimised for bauxite, gallium results from the test are pending, and the company has yet to show that the recovered metals can be purified economically at scale.
Optimisation and demonstration plant move to centre stage
Mount Ridley plans to optimise Selectro for bauxite, test aluminium and iron separation and purification, and run further third-party programs. It also expects to treat flotation concentrates from its Grass Patch feed after pending assay results are received. The company says the first bauxite result arrived ahead of the previously indicated first-quarter 2027 timetable for third-party testing.
The next commercial marker will be a Selectro demonstration plant, which Mount Ridley says it is continuing to design and construct and remains funded to progress. The proposed plant is intended to test the flowsheet at larger scale and generate bulk product samples for potential partners and offtakers. Until those results arrive, the most important question is whether the attractive first-pass chemistry survives larger, more representative feed samples and the costly steps between leaching and a saleable product.
Bottom Line?
The recovery figures are promising, but the investment case now depends on representative testing, product purification and demonstration-scale economics rather than the first leach result alone.
Questions in the middle?
- Can Selectro maintain its aluminium and iron recoveries on larger, representative Darling Range and other bauxite samples?
- Will Mount Ridley demonstrate saleable aluminium and iron products after separation and purification?
- What capital, reagent, energy and permitting requirements will emerge as the demonstration plant is designed?