Bafertisite Mineralogy and Occurrence State of Niobium in Bayan Obo Deposit

Bafertisite, the first new mineral found in the Bayan Obo deposit, is relatively weakly studied in terms of its morphological features, symbiotic assemblages, and mineralogical genesis. Based on some coarse-grained bafertisite crystals with complete crystal form found in recent years, a detailed mineralogical and mineral chemical study was carried out using polarized reflectance microscope, field emission scanning electron microscope, field emission electron microprobe and other analytical test instruments. The results show that: the color of bafertisite is brownish red to yellowish red, and the grain size is around 0.3-1.0 mm, which is in tabular, radial and columnar forms in aegirine type ore, riebeckite-mica type ore, dolomite type ore, and H9 slate, and the main co-occurring minerals are aegirine and riebeckite, meanwhile, by the influence of late hydrothermal fluids, the mineral crystals underwent different degrees of alteration and accounted for, and the ilmenite, siderite, and barite and other minerals. Due to the alkaline hydrothermal fluid Nb⁵⁺ and Ti⁴⁺, Fe³⁺, etc. occurred to varying degrees of homogeneous substitution of analogs, bafertisite crystals contain a certain amount of Nb₂O₅, and radial bafertisite has the highest content of niobium, 1.72%, in addition to baotite, niobobaotite, bafertisite is another typical niobium-containing Ba, Ti, Fe silicate minerals. In summary, it is initially believed that the crystalline distribution of bafertisite is mainly controlled by the action of sodic fluids in the ore area, and that tabular bafertisite, radial and columnar bafertisite represent the early and late fentization process in the orebody, respectively. In addition, Ti-bearing minerals in the orebody are important niobium minerals and niobium-bearing minerals that deserve attention in subsequent studies.