Characterization of a carbonatite-derived mining tailing for the assessment of rare earth potential

Depletion of high-grade deposits of rare earth elements (REEs) has led to increased interest in reprocessing mining tailing, particularly from carbonatite-related deposits. This is because most of the world's REEs are produced from such deposits. The objective of this study was to physically, geochemically, and mineralogically characterize a carbonatite-related tailing from an Australian mine site to assess the REEs recovery potential. The tailing sample sourced from the mine site was analyzed by dry screening, laser particle size analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Inductively Coupled Plasma Mass Spectrometry, and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). The results revealed that tailing consisted of mainly fine particles with 50 wt% below 61 µm. The geochemical results showed that the tailing consisted mainly of iron (Fe), and REE accounted for over 50% and 9% of the mass, respectively. The identification of major mineral phases by XRD followed by verification by SEM-EDS found monazite and florencite were the main REE-bearing minerals. The main gangue mineral is identified as goethite. The metallurgical balance showed that over 70% of the mass, REE, and Fe were concentrated in finer particle fractions below 63 µm. The SEM-EDS-based mineral liberation analysis found that REE-minerals were primarily associated with goethite and were locked within the latter in larger particle sizes over 100 µm. However, the smaller (<50 µm) REE-mineral grains were mostly liberated. The findings of this study suggest that light grinding of the particle fractions above 63 µm would potentially liberate the locked REE-minerals and subsequent separation by gravity, magnetic, and flotation processes can be tested to make REE concentrate. Because the sample is fine-grained, direct hydrometallurgical processing could potentially be effective to recover REE from this tailing.