Australian Silica Quartz Bauxite Delivers 92% Aluminium Recovery in Selectro Test
Key Takeaways
- Selectro™ recovered 91.9% of aluminium and 96.7% of iron from Darling Range bauxite in its first third-party test, run by ALS on material supplied by ASQ.
- The leach ran below 100°C and left a small, pH-neutral, silica-rich residue of about 25% of feed mass, against Bayer digestion that starts around 145°C and generates red mud.
- The 1 kg composite came from 16 selected samples across four drill holes and is not intended to represent the deposit, so nothing has yet been proven at scale.
- Gallium results from the bauxite test are due within a week, while Grass Patch flotation concentrate assays are still pending.
- Management is fast-tracking a Selectro™ demonstration plant and says it remains funded, though no funding amount is disclosed.
Selectro™ delivers 92% aluminium recovery in first third-party bauxite test
Mount Ridley Mines (ASX: MRD) has reported 91.9% (92%) aluminium and 96.7% (97%) iron recovery from a Darling Range bauxite composite supplied by Australian Silica Quartz Group Ltd (ASX: ASQ) and tested by Australian Laboratory Services (ALS). It is the first third-party test of the wholly owned, patent-pending Selectro™ Process, and a useful data point for aluminium recovery from bauxite.
This is also the first application of Selectro™ beyond the Grass Patch Complex and its first test on bauxite. The result came on a first pass basis, with the underlying chemistry yet to be optimised for bauxite feed.
So what does that mean for you? It suggests the technology may have a use well beyond Mount Ridley’s own resource, although nothing has yet been shown at scale.
Allister Caird, Managing Director & CEO
“This is a remarkable result for Selectro™.”
“The underlying chemistry has not yet been optimised for bauxite and we expect further improvements through that work.”
The company also said the result strengthens its conviction to fast-track the design and construction of a Selectro™ demonstration plant.
Test results at a glance
The testwork used a composite prepared from 16 vacuum drill samples from four drill holes across the Athena and Ceres prospects of ASQ’s Darling Range bauxite project. Recoveries are reported as metal extracted to solution, calculated from residue and head assays.
| Element | Composite head grade | Selectro™ recovery |
|---|---|---|
| Aluminium (as Al2O3) | **41.9%** | **91.9%** |
| Iron (as Fe2O3) | **13.6%** | **96.7%** |
Key facts about the test:
- The composite weighed approximately 1 kg, blended from samples ASQ collected from vacuum drilling completed in 2013 and 2014.
- The leach was conducted at below 100°C.
- The dried leach residue was approximately 25% of the original feed mass and consists predominantly of silica.
- More than 90% of the silica remained in the residue.
Treat the numbers with care. The composite was prepared from selected samples supplied by ASQ for the purpose of testing Selectro™ and “is not intended to represent the deposit as a whole”. Mount Ridley has also not independently verified ASQ’s drilling, sampling or survey data.
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Why red mud and the Bayer process matter to investors
Red mud is the headline environmental issue in alumina refining, and it is the problem Selectro™ is being positioned against. Understanding the conventional process shows why a different residue matters.
The Bayer process explained
Almost all of the world’s alumina 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. That leftover residue is bauxite residue, known as red mud.
Typically one to 1.5 tonnes of red mud is generated for every tonne of alumina produced. That equates to an estimated 150 to 200 million tonnes each year, with global stockpiles estimated at around 4 billion tonnes.
The Selectro™ test left a small, pH-neutral, silica-rich residue instead. Because the aluminium and iron both went into solution, the company says the iron can be precipitated through a simple pH adjustment as an iron oxide product with the potential to be sold.
For investors, the angle is twofold. The test ran well below Bayer digestion temperatures, which the company says has the potential to reduce energy demand and associated emissions, and the process avoids generating red mud, a waste stream the source describes as a significant environmental and social challenge for the industry.
Where Selectro™ could fit
The company outlines several potential roles for the technology:
- A potential processing route for high reactive silica bauxite deposits that are currently uneconomic under the Bayer process.
- Smaller, cost-effective Selectro™ plants at deposits too small to justify a conventional refinery.
- Licensing of Selectro™ to refiners, which the company sees as the most direct pathway to adoption.
Every one of these is a potential, not a demonstrated, outcome. The demonstration plant is intended to test the flowsheet and process economics at a larger scale.
Market opportunity: aluminium, gallium and scandium
Primary aluminium production reached approximately 73.8 million tonnes in 2025. At an LME price of approximately US$3,200 per tonne in late September 2026, the company calculates that output is worth in the order of US$235 billion, an indicative figure only.
Gallium shows how much value can sit inside bauxite. Primary gallium is recovered almost entirely as a by-product of alumina refining, and the final investment decision announced in July 2026 for a gallium plant at Alcoa’s Wagerup alumina refinery reflects the strategic value placed on it.
Mount Ridley’s gallium results from the bauxite test are not yet available. They are expected within a week and will be reported once received, so no gallium recovery from bauxite has been shown.
Scandium links the story back to Grass Patch. Scandium is used as an alloying addition to aluminium, and Mount Ridley is advancing scandium alloy development through its Kick-Start collaboration with CSIRO’s Lab22 additive manufacturing group.
| Issue | Fact from the announcement | Potential impact for Selectro™ |
|---|---|---|
| Red mud | Estimated **150 to 200 million tonnes** generated each year | Test produced a small, pH-neutral, silica-rich residue instead |
| Reactive silica | Bauxite with high reactive silica is often uneconomic to refine | Potential route for deposits uneconomic under Bayer |
| Small deposits | Many are too small to justify a conventional refinery | Potential for smaller, cost-effective plants |
| Gallium | Bauxite test results expected within a week | Pending; not yet reported |
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Next steps and commercialisation pathway
The company says the result gives it great confidence in the testwork ahead. Its listed next steps are:
- 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.
- Assaying of Grass Patch flotation concentrates (assays pending), which 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, which will validate the flowsheet at scale and generate bulk product samples for prospective partners and offtakers.
- Engagement with strategic partners and government programs.
The company states it “remains funded to progress the demonstration plant”. No funding amount is disclosed, and the announcement contains no financial or share price data.
For investors, the thesis is a diversified platform: a potentially licensable processing technology alongside the Grass Patch heavy rare earths, scandium and gallium resource. The risks are equally clear, with a first pass result, an unrepresentative composite, pending gallium data and no proof at scale. Those are the markers to watch as further testwork reports.
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