Abstract:Electronic microprobe technique was applied to analyze Mine 745 uranium ores and tailings in terms of their mineralogy and chemistry, and according variations before and after bioleaching. The results show that uranium minerals from the mine are mainly consisted of pitchblende, with a small portion of coffinite, uranothorite and brannerite. Those uranium minerals species mainly present themselves in occurrences of irregular dendritic or thin vein, granular, star-shape in mineral fractures, with some wrapped in other minerals. The particle size is relatively big ranging from 10 μm to 100 μm above. After bioleaching, the uranium content in tailings evidently reduce, although the species, mainly presented inside the quartz grains with the size of 1~2 μm, remain the same. The results indicate that pitchblende and uranothorite in fissures are easily leached while those wrapped in quartz grains are hard to leach.