Rapid identification of rare earth element bearing minerals in ores by cathodoluminescence method

Abstract

In mineral ores, the identification of monazite, bastnäsite, and xenotime, which are currently exploited rare earth element bearing minerals, is important for the development of the mines that reserve rare earth elements. A conventional method for their identification, an electron probe microanalysis, is time-consuming. Here a method to rapidly identify these minerals is presented by acquiring cathodoluminescence (CL) images and spectra. Monazite, xenotime, and bastnäsite emitted red, blue-green, and red luminescence in their CL images, respectively. We detected CL peaks related to some rare earth elements, such as Ce, Tb, Pr, Sm, and Nd for monazite; Gd, Ce, Tb, Er, Tm, Dy, Sm, and Nd for xenotime; and Pr, Sm, and Nd for bastnäsite using our custom CL spectrometer. Monazite, bastnäsite, and xenotime are distinguishable from other minerals that coexist with these three minerals based on their CL colors, intensities, peak wavelengths, and peak intensity ratios. The analysis time to acquire the CL images and spectra was within 100 s. Therefore, the acquisition of CL images and spectra contributes to the development of the rare earth element reserving mines and the sustainable supply thereof.