Apatite content and distribution in organic-rich particles

Abstract

X-ray computed tomography (CT) can be used to generate 3D models of physical structures, but there is no explicit chemical or mineral information in a CT dataset. An image registration method is described here that uses CT and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) to measure the volume of the apatite-bearing phase, φP, and the local variations in apatite concentration, CA, in individual low-grade apatite-ore particles. This method also permits a calculation of the apatite mass fraction, wA (from φP and CA), in individual particles, which effectively reconciles the X-ray signal to apatite grade. It was found that wA varied between 11 and 65 wt. % in individual particles, compared to the apatite content (51 wt. % by X-ray diffraction) of the bulk sample, which indicates the low-grade apatite ore studied was a mixture of high- and low-grade particles. This study establishes a clear link between the X-ray CT signal, grade distribution, and the qualitative description of the apatite-bearing phase morphology within single particles. Process options for this ore, with further study, could be based on the selective removal, or pre-concentration, of low-grade coarse particles before they enter the comminution circuit.