European Resources Limited (ASX: ERE) has reported encouraging results from metallurgical testing conducted by ANSTO Minerals on historical lanthanide concentrate from its Korsnäs project in Finland. The latest test work, which utilised a direct acid-bake and water-leach process, achieved a successful extraction rate of 83% for magnet rare earths.

The results demonstrated that praseodymium and neodymium were extracted at 88% and 83% respectively. Total rare earths plus yttrium (TREY) extraction reached 86%. These figures confirm that the monazite-hosted minerals within the concentrate respond effectively to conventional acid-bake processing.

"ANSTO's latest results are an important de-risking step for Korsnäs. The direct bake test has shown that the key magnet rare earths, praseodymium and neodymium, can be extracted at high levels from the historical concentrate using the acid-bake route."

"The key point is that this is no longer just a question of what minerals are in the concentrate. ANSTO has now demonstrated that the main value-bearing monazite component responds well to treatment, while also clearly defining the next job to optimise the pre-leach step so that the apatite-hosted heavy rare earths are also properly addressed."
— Jason Beckton, Managing Director

The test results also highlighted that certain heavy rare earths, such as terbium and dysprosium, showed lower extraction rates of 49% and 43%. Technical consultants noted this is consistent with a portion of the rare earth assemblage being hosted in apatite, which becomes less soluble under the current bake conditions.

To address these findings, upcoming development efforts will focus on the optimisation of calcite removal and specific apatite pre-leach conditions. The next phase of the program will involve testing combined pre-leach and acid-bake sequences to improve overall rare earth recovery and refine the downstream flowsheet.

Read the full announcement: ANSTO Initial Testing Extracts 83% Magnet Rare Earths