Abstract: To improve the comprehensive utilization rate of the polymetallic and nonmetallic mineral resources such as i ron,rare earths,and fluorite in Bayan Obo,a process mineralogy study was carried out on the mediumlow grade oxidized ores that had been stockpiled for many years at the Bayan Obo deposit with Xray diffraction (XRD) analysis,chemical composition analysis,scanning electron microscopy (SEM),and mineral liberation analyzer (MLA).The results show that the runofmine ore has a TFe grade of 28.74% and an REO grade of 5.45%.The main valuable minerals are magnetite/hematite,monazite, bastnaesite,and fluorite,while the main gangue minerals are amphibole and dolomite.Iron mainly occurs as hematite and mag netite.Iron is predominantly distributed in the coarser size fractions,whereas the rare earth elements are mainly concentrated in the finer fractions.The liberation degrees of the major minerals are relatively low,and the interlocking relationships among dif ferent minerals are very tight.Therefore,it is difficult to achieve efficient recovery of iron,rare earths,and fluorite by conven tional beneficiation processes.

Key words: Bayan Obo medium-lean oxidized ore,process mineralogy,hematite,rare earth