American Rare Earths Ltd (ASX:ARR, OTCQB:ARRNF) has delivered a “major technical breakthrough” at its flagship Halleck Creek Project, producing a mixed rare earth oxide (MREO) for the first time using the updated preliminary pre-feasibility study (PFS) processing flowsheet.
The result confirms that rare earths from Halleck Creek can be converted into high-value metallic oxides — the precursor required for separated products such as neodymium-praseodymium (NdPr), terbium (Tb), samarium (Sm) and dysprosium (Dy). These magnet metals are central to defence technologies, clean energy infrastructure and advanced manufacturing.
Halleck Creek Mixed Rare Earth Oxalate (left) and Mixed Rare Earth Oxide (right).
Breakthrough oxide production underpins PFS flowsheet
ARR generated the MREO from a purified pregnant leach solution (PLS) produced during impurity-removal test work. Metallurgical specialists SGS Canada completed the process in two stages: first precipitating a mixed rare earth oxalate using oxalic acid, then calcining the material at 1,000°C to form the oxide powder.
Importantly, calcining oxidised cerium from Ce³⁺ to Ce⁴⁺, preventing it from dissolving in the reagent used for later solvent-extraction steps — a technical advantage that supports efficient downstream separation.
Test work showed strong recoveries across the rare earth suite. Under a 110% stoichiometric dose of oxalic acid, total rare earth recoveries averaged around 97%, while magnet rare earths — Nd, Pr, Sm, Tb and Dy — averaged about 98%.
Additional bench-scale testing using ion exchange removed 97% of uranium from solution in a single step and 99% across the full neutralisation and ion-exchange sequence, further improving downstream processing quality.
PFS momentum builds as flowsheet simulation begins
With MREO production now demonstrated, ARR has commenced solvent-extraction simulation work using MetSim. The results will help define refinery specifications and cost assumptions for the Halleck Creek PFS, where solvent extraction is considered a well-established and comparatively straightforward stage of the value chain.
Optimisation programs are progressing in parallel. Comminution testing of Cowboy State Mine ore at FLSmidth and Loesche is nearing completion, with bulk ground samples heading to Nagrom for reflux classifier concentration and induced roll magnetic separation. Wet high-intensity magnetic separation test work with Eriez is also scheduled.
ARR plans to run a full pass-through of the mineral processing flowsheet using concentrate from these programs to validate all hydrometallurgical results to date.
Strategic significance for US rare earth supply chains
Located on Wyoming State land with streamlined permitting pathways, Halleck Creek offers potential for large-scale, low-strip mining alongside onsite processing and separation facilities.
ARR says the latest milestone strengthens the technical foundations of the upcoming PFS and reinforces the project’s importance as a future source of US-controlled rare earth supply — an area of growing strategic focus as the country seeks to reduce its longstanding reliance on Chinese imports.
The company continues to collaborate with US government-supported research programs and advance environmentally responsible extraction technologies as Halleck Creek moves towards its next development phase.