This article is a sponsored feature from Mining.com.au partner OD6 Metals. It is not financial advice. Talk to a registered financial expert before making investment decisions.
Mixed rare earth carbonate is a chemical precipitate containing a mixture of rare earth elements (REEs), typically in the form of their carbonates.
MREC is an intermediate product – after mining and leaching rare earth ore, companies precipitate the REEs into a carbonate form, which can then be sent to separation/refinery plants.
Rare earth refineries (solvent-extraction plants) commonly accept MREC because it’s a standardised, transportable feedstock from which high-purity rare earth oxides and metals can be produced.
Essentially, the quality of the MREC affects how much refiners are willing to pay. The higher the quality, and lower the impurity of the MREC means companies can command a premium.
The make-up of OD6 Metals’ (ASX:OD6) Splinter Rock Rare Earth Elements Project in Western Australia is one that opens up a plethora of potential end-user avenues for the minnow.
Inside OD6’s rare earths edge
Impurities like iron, aluminium, phosphorus, silicon, or even radioactive elements such as uranium and thorium) can significantly reduce the value of the carbonate, increase the costs to remove, or make it problematic for downstream processing.
“Clean” MREC has very low levels of these and has a high proportion of rare earth oxides, meaning more of the valuable REEs are actually in the product. OD6 Metals is in this category. Lower levels of radioactive impurities in clean MREC also means fewer environmental or regulatory concerns with storage, transport, and further processing.
OD6 has proven it can produce a clean, high-quality mixed rare earth carbonate, which is a product highly sought after by several end users.
In early October 2025, the emerging rare earths producer selected a preferred flowsheet with the aim of producing MREC and mixed rare earth hydroxide (MREH).
Flowsheet testing undertaken by the Australian Nuclear Science and Technology Organisation (ANSTO) achieved a MREC recovery of about 56% total rare earth oxide (TREO), and a MREH recovery of roughly 59% TREO.
The process also demonstrated low levels of aluminium, iron, phosphorus and silicon impurities, and extremely low uranium and thorium content of less than 0.001%.
For OD6, overall recoveries of the most in-demand magnet rare earths, neodymium and praseodymium (NdPr), reached around 75%. These magnet-feed rare earths, which also include dysprosium and terbium, are essential for producing high-performance permanent magnets. These magnets are used in EV motors, wind turbines, electronics, and for the defence sector, among others.
In rare company
As Managing Director Brett Hazelden explains to Mining.com.au, OD6’s focus is firmly on ensuring it can remove all of the impurities to produce a clean, high-quality concentrate.
“What it does is allows us to sell to the French who have got the highest requirements in terms of uranium, thorium and impurities,” Hazelden tells this news service.
“It also allows us to sell into Canada, Estonia, and other Asian markets.”
Hazelden notes it also opens the doors for OD6 to be able to sell into Lynas Rare Earths (ASX:LYC) and MP Materials (NYSE:MP), which are the existing producers looking to go downstream.
“It also allows us to sell into Canada, Estonia, and other Asian markets”
If OD6 decides to take it a step further and produce rare earth oxides, this could open up a direct line to the magnet producers.
The high value magnet rare earths – neodymium, praseodymium, dysprosium and terbium – account for some 23% of the TREO grade at Splinter Rock, which hosts a resource so far of 682 million tonnes @ 1,338 parts per million for 910,000 tonnes of contained TREO.
The magnet rare earths provide about 205,000 tonnes of the contained resource.
“So 90% of the value will come from those four elements,” Hazelden says.
Splinter Rock is a clay-hosted REE deposit, which generally has a higher percentage of magnet rare earths than hard rock deposits.
Being clay-hosted also means Splinter Rock will have a lower capital cost. With respect to processing, no flotation or any other pre-concentration steps are required because the clay can be leached readily at ambient temperatures, therefore avoiding the need for expensive high temperature leaching.
The science behind the recoveries
OD6 plans to subject the clay to heap leaching, which is a commonly used, environmentally responsible method for extracting rare earths and gold, as well as several other commodities.
It is also incorporating nanofiltration into the process, which Hazelden labels a “game changer” as it reduces the volume of reagents needed by over 60% and, in turn, the cost.
“Reagents are probably one of our top two costs generally,” he tells this news service.
Nanofiltration is more selective than ultrafiltration, separating out the hydrogen and chloride and recycling them back into the process to be used again.
“We can recycle about 85% of the hydrochloric acid back to the heap leach, which means it keeps on getting used and decreases our acid consumption by that amount,” Hazelden continues.
“So there’s a big capital and operating cost saving there for us.”
Another avenue OD6 has identified that may be considered down the track is the production of samarium and yttrium oxides, which are both used in nuclear reactors for clean power generation and nuclear medicine.
Samarium is also used in the manufacture of high-temperature samarium-cobalt magnets for headphones, electric motors and aerospace applications. Yttrium, meanwhile, is used in superconductors, televisions and light-emitting diodes.
“I think you need to leave the door open, with this geopolitical world, to be able to do some things that might not be rational but obviously make economic sense if they’re going to fund you”
“We might look at doing that, as a stage two but it would have to be government-funded from that point of view to balance the economics,” Hazelden explains to Mining.com.au.
“I think you need to leave the door open, with this geopolitical world, to be able to do some things that might not be rational but obviously make economic sense if they’re going to fund you.”
On 12 November, OD6 announced that a peer reviewed scientific paper detailing research undertaken at its flagship Splinter Rock project has been published in the international journal Ore Geology Reviews.
In simple terms the research paper explains how integrating landscape evolution, mineralogy, geophysics, and geochemistry aids in understanding processes for REE enrichment.
It highlights three regolith units — saprock, saprolite, and transported being identified, with the highest REE concentrations in saprolite. Also, changes in conductivity (AEM) and kaolinite crystallinity (hyperspectral) identified key interfaces within the regolith.
Hazelden says OD6 continues to work closely with Australia’s leading research institutions to build a deep scientific understanding of the Splinter Rock Rare Earth Project and develop advanced technologies for REE discovery and extraction.
“We are proud to be one of the few companies globally that base development decisions on such detailed, peer –reviewed science. The collaboration with CSIRO, Murdoch and Monash has provided valuable insights into how and where rare earths occur at Splinter Rock,” he says.
“In the current geopolitical environment, and as one of Australia’s largest and highest-grade clay-hosted REE deposits, Splinter Rock provides governments and industry with a project based on real science, plus in-depth research and development, sourced from a stable jurisdiction.”
Playing the long game
The current resource is based on drilling of less than 10% of the clay basins identified. Hazelden says Splinter Rock could exceed multiple billions of tonnes that could provide decades and decades of mine life, but the focus for OD6 is bringing a more modest resource into production to generate cashflow to pay off debt and fund resource growth.
“If you want a 20-year mine life you only need 100 million tonnes,” he notes.
“So the question is, why do you need billions of tonnes? You just need to find the right 100 to 200 million tonnes, and Inside Centre for us has 110 million tonnes and it’s still open in multiple directions.
“The value for the company is getting through the metallurgical testing and getting it to the next stage in terms of being able to do offtakes and financing and all those arrangements.”
Inside Centre is the cornerstone prospect of the broader 949km2 Splinter Rock project. The prospect hosts direct extensions of thick, high-grade REE zones within the Centre Basin that extends for over 30km to the northeast.
Inside Centre currently has an indicated resource of 119 million tonnes @ 1,632ppm. Prior testwork on Inside Centre samples has resulted in heap leach recoveries of up to 79% magnet rare earths, with consistently high NdPr recoveries of about 80%.
Local company, global peers
While the project is slightly lower in grade than Meteoric Resources’ (ASX:MEI) Caldeira and Viridis Mining and Minerals’ (ASX:VMM) Colossus projects, the TREO recoveries from Splinter Rock are roughly 32% to 36% higher than these two Brazilian projects.
The capex for the two clay-hosted projects is estimated to be between US$350 million ($538.5 million) and US$445 million ($684.6 million) because they will be utilising leach tanks, thickening, clay washing, and solid liquid separation.
Hazelden believes Splinter Rock will be a lower capex, more inline with Ionic Rare Earths’ (ASX:IXR) Makuutu project in Uganda.
“If you look at say IXR as a comparable heap leach, they estimate a capex of about US$120 million versus US$400 million for a tank leach, so we’ll sit somewhere in between that,” he tells Mining.com.au.
OD6 has collected 2-2.5 tonnes of rare earth bearing core to support ongoing metallurgical optimisation and feasibility studies.
The metallurgical core program targeted zones within Inside Centre that best represent an area of consistent geology, prior metallurgical outcomes, low stripping ratios, significant grades and planned early stage mining areas.
Samples have been sent to ANSTO for heap leach, impurity removal, and rare earth product optimisation testwork. The bulk core samples will enable ANSTO and OD6’s technical team to refine and scale-up the flowsheet, while producing sufficient product for customer evaluation.
This will enable the production of over 1kg of premium, high-grade and low-impurity MREC and MREH, which will then be sent to global separation facilities to be utilised for offtake talks and to assess commercial payability options for the products.
Industry forecasts show magnet-REE demand is set to grow strongly through 2030, driven by the green energy transition – EV motors, wind turbines, and other electrification trends. Reports indicate sharply higher demand for magnet rare-earth oxides by 2030, which is why MREC output from projects such as Splinter Rock is critical.
Countries and companies are increasingly prioritising secure and diversified REE supply chains, not just raw ore, but quality intermediates like MREC. Even if a company has rare earth ore, turning it into a usable form is non-trivial. Producing high-quality MREC helps bridge mining operations and high-purity REE production.
According to the Resources & Energy Quarterly (March 2025), Australia is expecting meaningful MREC production growth. For instance, it projects 37,000 tonnes of MREC from Hastings’s Yangibana project.
That suggests MREC is becoming a mainstream intermediate product for new rare-earth supply chains, not just a niche. And one company well ahead of the pack is OD6 Metals.
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Images: OD6 & Mining.com.au
