Rapid recognition and quantitative analysis of niobium minerals by scanning electron microscopy/energy dispersive X-ray spectroscopy

The rapid recognition and quantitation of niobium-rich minerals is crucial for the study on the occurrence state of the niobium element in the ore dressing process. However, niobium minerals have the characteristics of relatively scattered distribution, small grain size and various morphologies, making recognition and quantitative analyses difficult. Herein, we developed a route to recognize and quantify niobium minerals by multi-stage filtration techniques: twice scanning electron microscopy (SEM) image scan and twice energy dispersive X-ray spectroscopy (EDS) acquisition. In this study, pyrite was used as the gray standard to guarantee the stability of gray threshold values of the same niobium grains, as well as the precision and accuracy of the EDS analyses were verified using niobium standards. In addition, the accuracy of classification of niobium minerals was confirmed by the principal component analysis method. The EDS data for the niobium standards and niobium minerals in this study were respectively consistent with the reference values and electron probe results, within the error limits. Our method minimizes the recognition and quantitative analysis time of niobium by gray calibration, twice SEM image scan and twice carrying out EDS acquisition by avoiding the quantification of unconcerned grains. The recognition and quantitative analysis method used in this study can support research on the rapid identification of fine mineral particles on a large scale, such as the seeking of rare earth minerals in rare earth deposits and dating minerals in extraterrestrial samples.