Critical Minerals-U-Th, Recoverable from the Placer Valuable Heavy Minerals in Mineral Sand Deposits

Critical Minerals (CMs) are important due to their high-tech industrial and strategic applications in many industries such as the green and renewable energy, electronics, alloys and super-alloys, metallurgy, space, nuclear, defence, fertilizer, etc. The heavy mineral sand (HMS) deposits constitute one type of ore deposit that is an important source of (a) Ti, Zr, Th, W and REE, (b) the industrial minerals such as diamond, sapphire, garnet and sillimanite, and (c) occasionally gemstones, with cost of their mining is much less as compared to that of mining of rocks. An overview of the global, including Indian, scenario on the HMS deposits is presented. Amongst the CMs, a few such as the REEs, Ti, Zr-Hf, V, Cr, Nb, Sc and phosphate, and nuclear fuels of U and Th occur in trace to major contents in the placer valuable heavy minerals (VHMs, such as ilmenite, rutile, monazite, zircon, sillimanite and garnet) of the shoreline and inland HMS deposits in India, as documented by the mineral chemistry of VHMs. These CMs, U and Th could be recoverable as value-added byproducts with (i) separation of individual VHMs by mineral beneficiation techniques on HMS deposits and (ii) processing of such VHMs by extractive techniques ̶ of extraction, separation, purification, smelting and refining ̶ together with appropriate additional R&D studies, with examples of LREEs, U and Th from monazite and HREEs from garnet. Furthermore, the silt-product (<63 microns grain-size) of mineral sand industry comprising above HMs, gangue like quartz and clays could also be a source for the above cited CMs-U-Th. The recovery and processing of the above cited CMs, U and Th from the VHMs and silt in HMS deposits have multiple benefits, including establishing their additional resources (e.g., from the present Indian monazite resource of 13Mte, it may be possible to recover ~6.5 Mte of ΣRE2O3 [with average of 50% ΣRE2O3 in monazite], ~3.25 Mte of phosphate [av. 25% P2O5], ~1.3Mte of ThO2 [av. 10% ThO2] and ~0.13Mte of U3O8 [~1% U3O8]), establishment of down-stream industries with employment generation and economic benefit to the mineral sand industry.