Mount Ridley Mines Selectro Recovers 92% of Bauxite Aluminium in First Test
Key Takeaways
- Selectro™ recovered 91.9% of aluminium and 96.7% of iron from a bauxite composite on a first pass, with the chemistry not yet optimised for bauxite.
- This is the first third-party test and the first outside the Grass Patch Complex, using Australian Silica Quartz Group's Darling Range samples, and it landed ahead of the Q1 2027 timeframe.
- The leach ran below 100°C against 145°C to over 250°C for Bayer digestion, leaving a small, pH-neutral, silica-rich residue instead of red mud.
- The test used a roughly 1 kg composite from 16 samples across four holes, and the Company stresses it is a proof of concept, not a statement on deposit economics.
- Gallium results from the bauxite test are due within a week, and Mount Ridley says it remains funded to progress its Selectro™ demonstration plant.
Selectro™ delivers 92% aluminium recovery in first third-party bauxite test
Mount Ridley Mines Limited (ASX: MRD, OTC: MRDMF) has reported 92% aluminium and 97% iron recovery from a composite bauxite sample supplied by Australian Silica Quartz Group Ltd (ASX: ASQ) from its Darling Range project in Western Australia. The result comes from the first third-party test of the Company’s wholly owned and patent-pending Selectro™ Process.
The result was achieved on a first pass basis, with the underlying Selectro™ chemistry yet to be optimised for bauxite feed. The leach left a small, pH-neutral, silica-rich residue in place of the caustic, iron-rich red mud generated by conventional Bayer refining.
For investors, the point is that Selectro™ has now worked on a feedstock outside the Grass Patch Complex, and outside the critical minerals sector. The announcement describes it as the first application of Selectro™ beyond Grass Patch and its first test on bauxite.
Allister Caird, Managing Director & CEO
“This is a remarkable result for Selectro™…”
“…This result supports the progress we have made and strengthens our conviction to fast-track the design and construction of a Selectro™ demonstration plant…”
When big ASX news breaks, our subscribers know first
Inside the test results
Here is what the testwork actually measured, and the limits the Company places on it.
Recovery figures
Recoveries are reported as metal extracted to solution, calculated from the residue and head assays. The head grade is the metal content of the starting sample.
| Element | Composite head grade | Selectro™ recovery |
|---|---|---|
| Aluminium (as Al2O3) | 41.9% | 91.9% |
| Iron (as Fe2O3) | 13.6% | 96.7% |
Both metals went into solution together. That matters because the leach was highly selective, leaving the silica behind.
Test details
Australian Laboratory Services (ALS) carried out the work. Key parameters from the announcement:
- The composite was prepared from 16 vacuum drill samples taken from four drill holes across the Athena and Ceres prospects of ASQ’s Darling Range bauxite project.
- The composite weighed approximately 1 kg.
- The dried leach residue was approximately 25% of the original feed mass, with more than 90% of the silica remaining in it.
- The test was conducted at below 100°C.
- The Company has not independently verified ASQ’s drilling, sampling or survey data.
- The composite was prepared from selected samples supplied for testing Selectro™ and is not intended to represent the deposit as a whole.
Treat this as a proof of concept on a small, hand-picked sample, not a statement about any deposit’s economics.
Why Bayer and red mud matter
The result only makes sense against the process it hopes to challenge.
Bayer process explained
Almost all of the world’s alumina (the refined oxide from which aluminium metal is made) is produced through the Bayer process, developed in the late 1880s. Crushed bauxite is digested in hot concentrated caustic soda under pressure, dissolving the aluminium while iron, titanium and silica bearing minerals remain as a fine insoluble residue.
Digestion temperatures range from around 145°C for gibbsite rich bauxite, such as that of the Darling Range, to more than 250°C for boehmite and diaspore rich bauxite mined in many other regions. The Selectro™ test ran below 100°C, which the Company says has the potential to reduce the energy demand and associated emissions of alumina refining.
The red mud problem
The residue left after digestion, known as red mud, is the largest waste stream of the aluminium industry. Typically one to 1.5 tonnes is generated for every tonne of alumina produced, equating to an estimated 150 to 200 million tonnes each year, with global stockpiles estimated at around 4 billion tonnes.
Storage is a long-term issue. The announcement points to the 2010 failure of a red mud storage facility at Ajka in Hungary as an example of containment risk.
Red mud typically contains 30% to 50% iron oxide, and in the Bayer process that iron is discarded with the residue. In the Selectro™ test, the iron went into solution and can then be precipitated through a simple pH adjustment as an iron oxide product with the potential to be sold.
Market scale
Global primary aluminium production reached approximately 73.8 million tonnes in 2025. At an LME aluminium price of approximately US$3,200 per tonne in late September 2026, that output is worth in the order of US$235 billion.
That figure was calculated by the Company as annual production multiplied by price, and is indicative only. It shows the size of the industry Selectro™ is aiming at, not a revenue forecast.
The next major ASX story will hit our subscribers first
Investment thesis and next steps
Where Selectro™ could fit
The Company sees licensing of Selectro™ to refiners as the most direct pathway to adoption, given the size of the established alumina industry. The demonstration plant is central to testing the flowsheet and process economics at a larger scale.
Selectro™ was developed on Grass Patch feed, which is dominated by kaolinite, the clay mineral responsible for reactive silica in bauxite. The Company positions it as a potential processing route for high reactive silica bauxite deposits that are currently uneconomic under the Bayer process.
It also sees potential for smaller, cost-effective Selectro™ plants at deposits too small to justify a conventional refinery, producing aluminium, iron and other products closer to the resource.
Gallium is the next data point. Gallium results from the bauxite test are expected within a week, and Selectro™ has previously demonstrated gallium recovery from Grass Patch feed. The announcement notes a final investment decision announced in July 2026 for a gallium production plant at Alcoa’s Wagerup alumina refinery in the Darling Range, expected to supply up to 10% of global gallium.
On scandium, Mount Ridley is advancing alloy development through its Kick-Start collaboration with CSIRO’s Lab22 additive manufacturing group. The Company says a single technology recovering scandium from Grass Patch and aluminium from bauxite positions it across both sides of the aluminium scandium alloy supply chain.
What comes next
The Company lists the following steps:
- Optimisation of the underlying Selectro™ chemistry for bauxite feed.
- Demonstration of the separation and purification steps to recover aluminium and iron products from the leach solution, either in-house or with the support of industry partners.
- Flotation testwork on Grass Patch feed has been completed, with assays pending, and the resulting concentrates will then be treated using Selectro™.
- Further third-party Selectro™ testing, with this first result delivered ahead of the Q1 2027 timeframe previously indicated.
- Continued progress on the accelerated design and construction of a Selectro™ demonstration plant. The Company remains funded to progress it.
- Engagement with strategic partners and government programs.
If further third-party testing holds up, the Company expects the opportunities to participate in the commercialisation of Selectro™ to broaden, through strategic partnerships and licensing.
Want the Next ASX Mining Breakout in Your Inbox?
Join 30,000+ investors receiving FREE breaking ASX mining and energy news within minutes of release, complete with in-depth analysis and the full announcement. Click the “Free Alerts” button at Big News Blast to stay ahead of the market the moment news breaks.