The Pre-Concentration of the Nechalacho Deposit: Selective Comminution

The Nechalacho deposit, located in the Northwest Territories, Canada, is a heavy rare earth element (REE) deposit. Of the various REE-bearing minerals in the deposit, zircon is of significant importance, due to its elevated heavy rare earth element (HREE) content. Previous studies investigating the use of gravity and magnetic separation in the processing of this ore showed that coarse particles following grinding were enriched in zircon, suggesting the potential for selective comminution. The current work investigates the possibility to selectively comminute gangue minerals and concentrate REE-bearing zircon into coarser size fractions. The ore was ground wet in a laboratory ball mill for various lengths of time (0, 10, 20, 30, and 40 min). The grind size which resulted in the greatest grinding characteristics (upgrading, recovery, liberation) for zircon was then processed by dense medium separation (DMS) to determine further upgrading could be achieved by gravity separation. ICP-MS was used to determine the distribution of zirconium and REEs, and QEMSCAN, to identify mineral phases, mineral liberation and the distribution of minerals for both the comminution study and the DMS test work.