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The rare-earth elements (REEs) have gained enormous economic and scientific attention due to their distinct properties and new applications. Nepheline syenite rock is an important primary source of rare earth minerals. The nepheline syenite rocks from the Rairakhol area, western Odisha, have been characterized for their rare earth mineralogical and textural characteristics. Preliminary beneficiation studies of these rocks were carried out to upgrade the REE values using falcon gravity separation and floatation technique. Hornblende, biotite, K-feldspar, albite, and nepheline are the major mineral constituents of the nepheline syenite where REE-bearing minerals occur as accessory minerals. The REE mineral phases present are zircon, sphene, apatite, allanite, britholite, and REE phosphate, with grain sizes ranging from 10 to 50 microns. Allanite and britholite occupy the intergranular spaces of major mineral phases and occur as thin lines or veins whereas sphene and zircon occur as inclusions within major mineral phases. The flotation study shows that the total REE content of the froth product could be enriched to 1696 ppm, which is three times more than the total REE content (563 ppm) of the feed sample. [ABSTRACT FROM AUTHOR]

The present article discusses the contrasting characteristics of fireclay from two stratigraphically and geologically different locations of Odisha, eastern India, viz. (i) Talabasta from Cuttack district (FC1) belonging to Upper Gondwana Formation and (ii) Basundhara coal mines (FC2) of Lower Gondwana Formation of Jharsuguda district. The study focuses on micro-morphological, mineralogical, and geochemical characteristics of fireclay from the above locations and compare between them in respect of their refractory applications. The micro-morphological and mineralogical analysis inferred the predominance of quartz, kaolinite in both samples along with minor halloysite, goethite, and ilmenite in their various fractions. Layered hexagonal kaolinite, nanohedral kaolinite aggregates, and cylindrical halloysite are recognized under FESEM in FC1. In contrast, in FC2, the kaolinite is poorly crystallized, appears as anhedral to subhedral grains, or aggregates of very fine clay. The compositional analysis using XRF of bulk and its two size fractions (−75 + 45 and −45 μm) indicates FC1 to be rich in SiO2 and shows relatively less Al2O3, Fe2O3, TiO2, and K2O content than FC2. FTIR pattern, DSC and TGA pattern, and ash fusion temperature between FC1 and FC2 also show some difference. It is surmised that both fireclay samples have desired heat resistance (> 1400 °C) needed for refractory application. However, the AFT of FC1 can be further enhanced by decreasing silica content, and the AFT of FC2 can be improved by reducing Fe content through its proper processing. [ABSTRACT FROM AUTHOR]