Mount Ridley Mines has fired a shot across the bow of the global alumina industry, with its patent-pending Selectro process recovering an impressive 91.9 per cent of aluminium from bauxite in its first third-party test.
The breakthrough could prove a game-changer for the company’s low-intensity process, with the biggest win hiding in what it doesn’t produce: the caustic, iron-rich “red mud” that has plagued alumina refining and the world-famous Bayer process for more than a century.
For 130 years, the Bayer process has been the undisputed king of alumina production. However, its reign comes at a cost, generating an estimated 150 million to 200 million tonnes of red mud waste annually, with global stockpiles now sitting at a colossal 4 billion tonnes.
In an unexpected challenge, Mount Ridley says its in-house Selectro process - originally designed to recover critical minerals from clay-hosted deposits - has not only demonstrated it can liberate aluminium but also recover 96.7 per cent of the iron from the same feed, all while operating at temperatures below 100 degrees Celsius – temperatures 50 per cent cooler than those required for Bayer.
Australian Laboratory Services (ALS) conducted the metallurgical testwork on a composite bauxite sample from Australian Silica Quartz Group’s Darling Range project in Western Australia.
Instead of the troublesome red mud generated by conventional refining, the Selectro leach left behind a small, pH-neutral residue weighing just 25 per cent of the original feed, potentially making waste storage safer and easier to manage.
More than 90 per cent of the silica remained locked in this residue, while the aluminium and iron were drawn into solution. The company says the iron can then potentially be precipitated out as a saleable iron oxide product, turning waste into a value stream.
Impressively, the result was achieved on the first pass, with the company noting that the underlying Selectro chemistry is yet to be optimised for bauxite.
Mount Ridley’s development of Selectro for its own clay-hosted critical mineral deposits at its Grass Patch project near Esperance is evolving into an unexpected beast for the company and perhaps the wider industry.
The in-house leach technology has previously achieved recoveries for a suite of critical minerals that more than double those of the industry-standard, high-cost hydrochloric acid leach process, including a whopping 56 per cent recovery of gallium, compared with zero from the conventional process.
Recovering 92 per cent of the aluminium and 97 per cent of iron on a first pass basis, while producing a silica-rich residue rather than the conventional red mud, is an exceptional result. The underlying chemistry has not yet been optimised for bauxite and we expect further improvements through that work.
The global primary aluminium market is a behemoth, with production of 73.8 million tonnes in 2025 valued at roughly US$235 billion (A$338B). Almost all of the required alumina is refined using the Bayer process, which is often constrained by “reactive silica” in the feed, locking up the valuable alumina.
As Selectro was designed to handle the high-silica clays at Grass Patch, it appears a perfect pairing to tackle these silica-rich bauxite deposits that are currently considered uneconomic for conventional refining.
This is especially relevant in Western Australia.
The Darling Range bauxite that was used in the test is known to produce unusually large volumes of residue, with some estimates suggesting two tonnes of red mud being generated for every tonne of alumina produced.
Additionally, Bayer red mud is highly caustic, typically registering a pH of 10 to 13, posing serious safety risks ranging from chemical burns and respiratory damage to corrosive dust hazards. Its thick, moisture-laden slurry is difficult to handle, while long-term stockpiles carry risks of contamination and potentially catastrophic dam failures.
Mount Ridley believes its revolutionary tech could open up substantial opportunities for smaller, cost-effective plants to be built near bauxite resources that are too small or too high in silica to justify a conventional refinery.
With gallium results from the bauxite test expected within a week, the company is now planning to optimise the Selectro chemistry for bauxite feeds to support an optimised demonstration.
The Bayer process has been the cornerstone of the aluminium industry for generations; however, its environmental legacy is a growing concern. In a world increasingly focused on sustainability, a low-temperature process that can recover multiple metals while turning a massive waste problem into a manageable, silica-rich byproduct could be more than just a curiosity - it could be a game-changer.
Is your ASX-listed company doing something interesting? Contact: matt.birney@wanews.com.au