For the first time we report alluaudite from India, which is metamict and is hosted in a zoned pegmatite, near Pisangan, Ajmer district, Rajasthan. Alluaudites known till date, all over the world, are non-metamict type. Therefore, the alluaudite reported from the area is the first locality in the world for the metamict-type of alluaudite. The most conspicuous features exhibited by the alluaudite are various types of cracks in different directions and shapes, including its isotropic nature. The calculated crystallographic parameters of the reported alluaudite are: a0 = 11.9874 Å, b0 = 12.5144 Å, and c0 = 6.4136 Å, β = 114.240 with unit-cell volume (V) = 877.31 Å3, which are in agreement with the values of alluaudite standard. Geochemical data indicates high content of P (32.30% P2O5), Fe (30.2% Fe2O3), Mn (10.62% MnO), besides Mg (7.71% MgO), Ca (5.60% CaO), Na (3.40% Na2O) and Si (2.30% SiO2), and appreciable amount of water of hydration (3.50% LOI). It is highly radioactive due to uranium (2.28% U3O8) and thorium (185 ppm Th). Calculated structural formula of the alluaudite is Na1+0.59Ca2+0.54Mn2+0.80Mg2+1.02Fe3+2.03Al3+0.037U4+0.043P5+2.45O12. The chondrite-normalised plot shows enrichment of HREE relative to LREE with pronounced negative Eu-anomaly (Eu/Eu* = 0.46). Such a high negative Eu-anomaly suggests extremely fractionated nature of the host pegmatite.
This paper presents results on the characterization and hydrometallurgical studies for the recovery of Rare Earth Elements (REE) from micro-granite type hard rock REE deposit of Bhatikheda, Siwana Ring Complex, Rajasthan, India. The total REE (TREE) content of the ore is 0.36%. Heavy REE (HREE) constitutes about 40% of the TREE by weight. Allanite, zircon and gittinsite were identified as the major REE bearing phases. The nature of occurrence of REE phases in the ore is widely varying with the presence of fully liberated grains to those which occur very finely disseminated in lighter gangue minerals. Physical beneficiation using gravity-based separation techniques gave suboptimal performance. Agitation leaching of ground ore with different mineral acids gave good solubilisation of light REE (LREE), about 75%, but the leach recovery of HREE was only 40%. However, sulfation roasting followed by aqueous leaching (SRAL) yielded leach recovery of 85% of total REE under optimised conditions. The lean tenor of TREE in the leachate coupled with its complex solution chemistry necessitated use of ion exchange (IX) process with strong cationic resin in lieu of conventional solvent extraction based separation and purification. The dissolved REE values from the purified liquor were quantitatively precipitated in the form of TREE fluoride using HF as the precipitant. The final product was about 90% pure on dry weight basis. An integrated process scheme for the recovery of TREE values from the Bhatikhera hard rock deposit is designed-
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