The pivotal role of particle size on REE enrichment and extraction efficiency: A multi-modal characterization and leaching study of bastnäsite ore

• REE enrichment quadrupled below 40 µm, validating size segregation as a critical pre-concentration step • Hydrometallurgical tests prove particle size is the governing control parameter for enhanced REE extraction • Automated Mineralogy confirmed bastnäsite content dramatically increased in the enriched fine fractions • Systematic multi-modal characterization offers a robust framework for optimizing global complex bastnäsite ores. A detailed multi-modal characterization and extraction investigation was performed on bastnäsite ore from Türkiye's Kızılcaören deposit to elucidate REE enrichment mechanisms across different particle sizes. The as-received ore was fractionated and rigorously analyzed using Automated Mineralogy (AM), ICP-MS, and XRD. Results revealed a strong dependency of REE concentration on particle size, particularly below 40 µm. Light REE content quadrupled from 2.5 wt.% (±0.83) to 10.6 wt.% (±3.00), while Heavy REE increased from 835.7 ppm (±346.33) to 3867.5 ppm (±1056.9), with high standard deviations suggesting uneven elemental distribution. Consistent with chemical data, AM analysis showed that the area occupied by REE minerals (bastnäsite, monazite, parisite, synchysite) increased from 2.6% to 3.8% in fractions