Calibrated X-ray micro-tomography for mineral ore quantification

Reyes, F.; Lin, Q.; Udoudo, O.B.; Dodds, Chris; Lee, P.D.; Neethling, S.J.

Abstract

Scanning Electron Microscopy (SEM) based assessments are the most widely used and trusted imaging technique for mineral ore quantification. X-ray micro tomography (XMT) is a more recent addition to the mineralogy toolbox, but with the potential to extend the measurement capabilities into the three dimensional (3D) assessment of properties such as mineral liberation, grain size and textural characteristics. In addition, unlike SEM based assessments which require the samples to be sectioned, XMT is non-invasive and non-destructive. The disadvantage of XMT, is that the mineralogy must be inferred from the X-ray attenuation measurements, which can make it hard to distinguish from one another, whereas SEM when coupled with Energy-Dispersive X-ray Spectroscopy (EDX) provides elemental compositions and thus a more direct method for distinguishing different minerals. A new methodology that combines both methods at the mineral grain level is presented. The rock particles used to test the method were initially imaged in 3D using XMT followed by sectioning and the 2D imaging of the slices using SEM-EDX. An algorithm was developed that allowed the mineral grains in the 2D slice to be matched with their 3D equivalents in the XMT based images. As the mineralogy of the grains from the SEM images can be matched to a range of X-ray attenuations, this allows minerals which have similar attenuations to one another to be distinguished, with the level of uncertainty in the classification quantified. In addition, the methodology allowed for the estimation of the level of uncertainty in the quantification of grain size by XMT, the assessment of stereological effects in SEM 2D images and ultimately obtaining a simplified 3D mineral map from low energy XMT images. Copper sulphide ore fragments, with chalcopyrite and pyrite as the main sulphide minerals, were used to demonstrate the effectiveness of this procedure.

Citation

Reyes, F., Lin, Q., Udoudo, O., Dodds, C., Lee, P., & Neethling, S. (2017). Calibrated X-ray micro-tomography for mineral ore quantification. Minerals Engineering, 110, https://doi.org/10.1016/j.mineng.2017.04.015

• Journal Article Type: Article
• Acceptance Date: Apr 21, 2017
• Online Publication Date: May 2, 2017
• Publication Date: Aug 15, 2017
• Deposit Date: May 10, 2017
• Publicly Available Date: May 10, 2017
• Journal: Minerals Engineering
• Print ISSN: 0892-6875
• Electronic ISSN: 0892-6875
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 110
• DOI: https://doi.org/10.1016/j.mineng.2017.04.015
• Keywords: X-ray micro-CT; Mineral liberation analysis; Mineral characterisation
• Public URL: https://nottingham-repository.worktribe.com/output/878071
• Publisher URL: http://www.sciencedirect.com/science/article/pii/S0892687517301103