- 01Selectro extracted 94.9% of gallium from Darling Range bauxite in a lab test.
- 02The leach also recovered 91.9% aluminium and 96.7% iron.
- 03Mount Ridley will test metal separation and purification.
Mount Ridley Mines (ASX: MRD) has extracted almost 95% of the gallium in a Western Australian bauxite sample using its Selectro process, adding a third metal to the strong recovery results achieved in its first third-party test.
The single leach also extracted 92% of the aluminium and 97% of the iron at a temperature below 100 degrees Celsius, providing an initial demonstration of the technology on material outside Mount Ridley’s own projects.
The sample came from the Darling Range bauxite project of Australian Silica Quartz Group (ASX: ASQ), with gallium results following aluminium and iron results released on 15 October.
Earlier work on its Grass Patch material demonstrated recovery of scandium, heavy rare earth elements, and gallium, while the latest test broadens the feedstocks assessed.
Mount Ridley will now investigate how to separate and purify the dissolved metals, a necessary step before any commercial product can be recovered.
Three Metals from One Leach
The composite was prepared from 16 vacuum-drilling samples collected across four holes at the Athena and Ceres prospects, with a calculated gallium head grade of 80 parts per million.
Detailed testing measured gallium extraction at 94.9%, aluminium at 91.9%, and iron at 96.7%, with each percentage representing metal transferred into solution rather than a final saleable product.
Mount Ridley considers the similarity between gallium and aluminium extraction consistent with gallium occurring largely in the gibbsite minerals that host much of the bauxite’s alumina.
The process left a silica-rich solid residue containing more than 90% of the original silica, rather than the red mud generated during conventional alumina refining.
The company attributes the improved gallium result relative to the earlier Grass Patch testing partly to adjustments in its reagent chemistry for the different bauxite feed.
Alternative Processing Pathway
Mount Ridley developed the Selectro technology as a recycled-reagent leach system capable of targeting multiple critical minerals within one circuit.
Whereas the conventional Bayer process typically transfers about 70% of bauxite-hosted gallium into its caustic liquor, leaving the balance in residue and requiring a dedicated circuit to recover gallium from that liquor, Selectro’s higher laboratory extraction result offers a potential alternative processing pathway, although the technology remains in testing and its separation and purification stages are still to be demonstrated.
“We have long held the view that technology is the most effective way to deliver a new source of gallium supply,” managing director Allister Caird said.
“This result builds on the strong recoveries achieved from our own critical minerals basket at Grass Patch, and has prompted us to turn our immediate attention to separation and purification pathways for both bauxite and Grass Patch feeds.”
Gallium Supply Concentration
Gallium is used in semiconductor applications including power electronics, communications, and defence systems, with demand for gallium nitride power devices forecast to grow 35% annually to US$3.5 billion by 2031.
China accounts for approximately 99% of primary low-purity gallium production, while the US has no domestic primary output, making alternative supply routes a focus for industry and governments.
China’s suspension of its gallium export ban on the US runs until 27 November, although export licensing and restrictions on supply to US military users remain in force.
Mount Ridley is progressing a second bauxite leach test to optimise its chemistry, further tests on third-party feedstocks, and work towards a Selectro demonstration plant alongside the metal separation studies.
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