European Resources Limited has lifted combined magnet rare earth extraction to 92% at its Korsnäs rare earth elements project in western Finland following bench-scale test work by ANSTO Minerals that incorporated calcite removal before acid baking.

The latest hydrometallurgical results improve upon an earlier direct acid-bake and water-leach test that achieved an 83% extraction rate for magnet rare earths. By introducing a hydrochloric acid pre-leach to remove calcite, the test work upgraded the total rare earths plus yttrium grade from 2.3 wt% to 3.9 wt% while keeping rare earth losses between 0% and 2%.

Individual recoveries across the rare earth suite advanced notably, led by neodymium at 92% and praseodymium at 94%. Heavy rare earth responses showed even larger gains, with terbium extraction increasing by 20 percentage points to 69%, dysprosium rising by 23 points to 66%, and yttrium jumping by 32 points to 75%. Total rare earths plus yttrium extraction rose from 86% to 93%.

ANSTO noted that removing calcite likely reduced the formation of calcium sulphate phases that trap rare earths, while also freeing up acid to attack monazite. The laboratory work utilised historical lanthanide concentrate stockpiled at the 100%-owned Korsnäs project, which is separate from the property's hard-rock Inferred Mineral Resource of 15.4 million tonnes at 1.00% total rare earth oxides.

"ANSTO's latest work has lifted combined magnet rare earth extraction from 83% to 92% after calcite removal. This is a sequential flowsheet-development story: identify the constraint, test it and measure the uplift. The result is a clear advance, and we intend to keep pushing through impurity removal and precipitation towards a bench-scale MREC product which will demonstrate the potential of our emerging and growing Finland rare earths project."

— Jason Beckton, Managing Director

Building on these results, European Resources plans to produce and characterise a bench-scale mixed rare earth carbonate sample from a purified rare earth-bearing solution. The company will also evaluate physical methods to reject calcite, including assessing the high-gradient magnetic separation pathway to reduce acid consumption and lower operating costs ahead of hydrometallurgical processing.

Read the full announcement: ANSTO Test Work Raises Korsnas Magnet REE Extraction to 92%