Australian Rare Earths Hits Downstream Milestone as Pilot Plant Produces First MREOH
Key Takeaways
- AR3 has successfully produced Mixed Rare Earth Hydroxide (MREOH) for the first time at pilot scale, completing the first full heap leach-to-intermediate product cycle at Koppamurra.
- The first heap leach column cycle processed approximately 8 tonnes of ore and generated approximately 5,000 litres of Pregnant Leach Solution at target rare earth leaching recovery rates.
- The MREOH precipitation circuit is now generating engineering data across five categories — reagent consumptions, residence times, solid-liquid separation, water balance, and product quality — feeding directly into DFS commercial design.
- AR3 plans multiple further MREOH precipitation campaigns targeting approximately 28 kL of Pregnant Leach Solution, with the pilot program scheduled to continue through December 2026.
- The next milestone is refining MREOH into first pilot samples of Mixed Rare Earth Oxide (MREO), which will be shared with prospective offtake partners to begin customer qualification.
Koppamurra pilot plant crosses into downstream rare earth production
Australian Rare Earths (ASX: AR3) has advanced its Koppamurra pilot plant beyond heap leaching and into downstream processing, producing a Mixed Rare Earth Hydroxide (MREOH) intermediate product for the first time at pilot scale.
The first heap leach column cycle processed approximately ~8 tonnes of ore and generated approximately ~5,000L of Pregnant Leach Solution (PLS) at target rare earth leaching recovery rates. That PLS has now been successfully processed through the MREOH precipitation circuit, with full recoveries of rare earths from the PLS to the MREOH in line with expectations.
The milestone marks AR3’s transition from demonstrating rare earth extraction to producing a concentrated intermediate rare earth product, a meaningful de-risking step on the path toward Definitive Feasibility Study (DFS) design and eventual commercialisation.
Travis Beinke, Managing Director and CEO
“The pilot program is off to an excellent start. We have successfully established rare earth recovery through heap leaching and are now validating the first downstream processing stage required to convert those rare earth-bearing liquors into a saleable product. The commencement of MREOH precipitation marks another significant step in demonstrating Koppamurra’s complete processing flowsheet at pilot scale.
This phase of the program is particularly important because it continues to generate the engineering and operating data necessary for DFS design and will produce material for further refining into representative MREO samples for customer engagement and qualification. The ability to continuously recover rare earths from Koppamurra leach solutions and produce a concentrated rare earth intermediate is another important de-risking milestone as we advance the pilot operation to producing our final MREO product.”
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What is mixed rare earth hydroxide, and why does it matter?
Rare earth processing follows a defined sequence, and understanding where MREOH sits in that flowsheet helps clarify why this milestone is significant. The Koppamurra process moves through four stages:
- Ore is mined and agglomerated, then stacked onto heap leach columns where a leaching solution dissolves rare earth minerals from the rock.
- Pregnant Leach Solution (PLS) is the liquid that drains from the heap, carrying dissolved rare earth elements — it is the output of the extraction stage.
- Mixed Rare Earth Hydroxide (MREOH) is produced by adding neutralising agents to the PLS in a precipitation reactor, recovering the rare earths as a solid intermediate product.
- Mixed Rare Earth Oxide (MREO) is the further-refined, saleable product that will be shared with prospective offtake partners for customer qualification.
MREOH is not the final commercial product. It is the intermediate that must be further refined into MREO before it can be evaluated by potential buyers. Validating this intermediate step proves the complete downstream flowsheet is functioning at pilot scale, which directly reduces technical risk heading into DFS design.
What the MREOH circuit is designed to deliver
The circuit utilises a continuous three-stage precipitation reactor where neutralising agents are added to recover rare earths as a Mixed Rare Earth Hydroxide product. Solid-liquid separation equipment and continuous thickening are incorporated to recover the rare earth-bearing solids.
The MREOH precipitation circuit is designed to:
- Validate continuous MREOH production from Koppamurra Pregnant Leach Solution
- Optimise precipitation operating conditions and reagent consumption
- Evaluate thickening, filtration and washing performance under continuous operating conditions
- Generate engineering design criteria for commercial-scale equipment selection and sizing
Barrens generated from the process will be evaluated for recycle opportunities as part of the broader demonstration of Koppamurra’s commercial flowsheet.
Engineering data feeding the DFS
Operation of the MREOH circuit is expected to generate a substantial body of engineering information across five categories. Each feeds directly into DFS commercial design:
- Reagent consumptions — quantifies chemical inputs required at commercial scale
- Residence time requirements — informs reactor sizing and throughput modelling
- Solid-liquid separation performance — determines filtration and thickening equipment specifications
- Water balance data — supports site water management design
- Product quality and impurity deportment — establishes whether the MREOH meets purity thresholds for downstream refining
| Data Point | Relevance to DFS Design |
|---|---|
| Reagent consumptions | Defines chemical input requirements at commercial scale |
| Residence time requirements | Drives reactor volume |
| Solid-liquid separation performance | Determines filtration and thickening equipment specifications |
| Water balance data | Informs site water management design |
| Product quality and impurity deportment | Confirms product purity and suitability for downstream MREO refining |
The information obtained from this phase will be incorporated into DFS activities, further de-risking the commercial design of the Koppamurra processing facility.
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Program timeline and the path to customer qualification
The demonstration plant remains on schedule, with the program planned to continue to December 2026. AR3 plans multiple further MREOH precipitation campaigns, targeting approximately 28 kL of Pregnant Leach Solution from the pilot heap leach columns.
The next step after MREOH production is further refining into first pilot samples of Mixed Rare Earth Oxide (MREO), which will then be shared with prospective offtake partners. Producing these MREO samples is a commercially significant step: it puts representative product material in the hands of potential buyers, enabling customer qualification to begin.
Beyond the pilot programme, the broader AR3 portfolio provides additional context for the company’s positioning. The Koppamurra Rare Earths Project in South Australia and Victoria has a Pre-Feasibility Study complete and a maiden Ore Reserve established, and has received a $5 million Australian Government grant to accelerate development. AR3 also holds the approximately ~8,000 km² Overland Uranium Project in South Australia, which has identified strong uranium discovery potential alongside a new niobium-rare earth carbonatite exploration target.
The Overland Uranium Project sits alongside Koppamurra as a second growth vector for AR3, with the calcrete-hosted discovery underpinning what the company describes as strong uranium discovery potential across the approximately 8,000 km2 South Australian tenure.
The company has indicated it will provide further announcements as MREOH production campaigns progress and as MREO product samples become available for customer qualification.
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