ANSTO Minerals has demonstrated high extraction rates of key magnet rare earths from Korsnäs historical concentrate, advancing confidence in the project’s downstream processing flowsheet.
- Praseodymium and neodymium extracted at 88% and 83%
- Total magnet rare earth extraction reaches 83%
- Heavy rare earth extraction limited by apatite-hosted minerals
- Pre-leach stage optimisation identified as next critical step
- Impurity removal challenges highlighted for downstream processing
High Extraction Rates Confirm Acid-Bake Viability
ANSTO Minerals, a division of the Australian Nuclear Science and Technology Organisation, has achieved a significant technical milestone in processing rare earth elements from the Korsnäs project in Finland. Their latest metallurgical testing on historical lanthanide concentrate demonstrated an 83% extraction of combined magnet rare earths, praseodymium and neodymium extracted at 88% and 83%, respectively, using a direct acid-bake followed by water leach method. Total rare earths plus yttrium (TREY) extraction stood at 86%, underscoring the strong response of the monazite-hosted rare earth fraction.
Heavy Rare Earths Extraction Reveals Processing Complexity
While light and magnet rare earths yielded robust extraction results, heavy rare earth elements such as terbium (49%), dysprosium (43%), and yttrium (43%) lagged behind. This discrepancy aligns with ANSTO’s mineralogical findings that a significant portion of heavy rare earths are hosted in apatite, which under current acid-bake conditions forms low-solubility calcium sulphate compounds, limiting extraction efficiency. These findings highlight the necessity of a complementary pre-leach step to effectively liberate apatite-hosted heavy rare earths.
Pre-Leach Stage to Optimize Rare Earth Recovery
ANSTO’s results build on prior work that identified monazite as the dominant rare earth host in Korsnäs concentrate, with apatite also playing an important role. The direct acid-bake test was intentionally conducted without a pre-leach stage to assess the untreated concentrate’s response. The data now point toward a combined processing flowsheet: a pre-leach phase to manage calcite and apatite behaviour, followed by acid bake and water leach to target monazite-hosted magnet rare earths. This approach aims to maximise overall rare earth extraction and mitigate the formation of insoluble by-products.
Impurity Management Emerges as Key Challenge
Alongside rare earth extraction, impurity behaviour was closely monitored. Aluminium extraction reached 46%, while uranium and thorium extractions exceeded 96% and 97%, respectively. The TREY to aluminium ratio improved in the leach liquor, yet the elevated uranium and thorium dissolution signals that impurity removal will be a critical focus in downstream processing. Effective management of these elements is essential to meet product specifications and environmental standards.
Next Steps Focus on Flowsheet Refinement and Scale-Up
European Resources Limited (ASX:ERE) is now poised to advance the Korsnäs project’s metallurgical development with a clear roadmap. ANSTO will prioritise optimisation of the pre-leach conditions, test combined pre-leach plus acid-bake sequences, and integrate hydrometallurgical pathways with beneficiation programs. These efforts aim to define a preferred downstream flowsheet not only for the historical concentrate but also for future testing of hard-rock ore from Korsnäs. This metallurgical progress complements recent exploration success, including a substantial increase in the project’s Exploration Target and new passive seismic anomalies detected around the mineral resource area.
Bottom Line?
ANSTO’s high magnet rare earth extraction from Korsnäs concentrate sharpens the processing focus, but impurity removal and heavy rare earth recovery remain critical hurdles.
Questions in the middle?
- How will optimisation of the pre-leach stage improve heavy rare earth recovery and overall process economics?
- What strategies will European Resources adopt to manage uranium and thorium impurities in downstream processing?
- How will these metallurgical advances influence the timeline and feasibility of progressing Korsnäs towards production?