Lectures > Lecture 3

Lecture 3 by Deshenthree Chetty, Mineralogy Division, Mintek. 200 Malibongwe Drive, Randburg, South Africa.

Title: X-ray computed tomography for process mineralogical applications.

Rooted in the medical industry, 3D computed tomography has, over the last few decades, found increased application in the characterisation of geological materials and associated process products – a key tenet in the discipline of process mineralogy. In particular, high-resolution X-ray computed tomography (HRXCT) finds application in the characterisation of economic minerals, many of which occur at micron-scale grain sizes in ore. The non-destructive nature of HRXCT imaging, the need for virtually no sample preparation, and the larger volume completely analysed, render the technique superior to conventional 2D microscopy and automated scanning electron microscopy techniques used in process mineralogy.

For geological materials, and especially in the analysis of ores, the ability to differentiate between minerals occurring in the ore is necessary. Theoretically, minerals can be differentiated based on their linear attenuation coefficients, however, overlaps in these require more detailed attention, e.g. the use of dual energy scanning. The quality of the 3D image, particularly optimal contrast and reduction in artefacts, is therefore important.

Additionally, minerals or phase calibration may be done through registering of 2D and 3D image information. Another key aspect for consideration is the spatial resolution, which is determined by the voxel (i.e. 3D pixel) size of the image. This should be smaller than the minimum size sought for a specific feature in the sample. Resolutions of up to sub-micron, even nano-scale, can be obtained with modern scanners, but this is often at the cost of sample size scanned.

A third, very important aspect is that of particle segmentation (as opposed to normal phase segmentation), which is necessary for the determination of a key process mineralogical parameter: mineral liberation. The talk will focus on these and other aspects of importance in the process mineralogy discipline, covering the hardware and software used to extract quantitative mineralogical information from a variety of ores and processes, necessary for mineral beneficiation.

Biography: Desh Chetty obtained her PhD in geology at the University of Johannesburg in 2008, an MSc in geology at UCT in 1998 and a BSc Honours in geology at the University of Natal in 1995. She heads the Mineral Science Group in Mintek’s Mineralogy Division, where she has worked for the last 26 years, with a focus on process mineralogy. This includes research into such areas as geometallurgy and mineralogical method development to add value to mineral beneficiation, for which X-ray computed tomography is a key interest. She was instrumental in the acquisition, in 2018, of a Zeiss Versa 3D X-ray microscope scanner, jointly owned by Mintek and the University of South Africa. She has previously collaborated with such partners as NECSA, the University of Stellenbosch and the University of Utah, for the 3D analysis of various ore samples and products.