Drill Core Scanning using MLA - Micro Methods for Macro Samples

SEM-based automated mineralogy represents an established mineral identification and quantification technique in the mineral processing industry. The technique is routinely used to characterise the mineralogy of various mining and plant-related products (e.g., feed samples, concentrates, leach residues etc.). Automated mineralogical analyses are typically conducted on small 20-30 mm diameter epoxy mounts of fine-grained milled material. In contrast, mineralogical analyses of larger samples, such as drill core, can be obtained by non-destructive analytical techniques, such as hyperspectral scanning, micro-XRF and computed tomography (CT). Hyperspectral and micro-XRF methods are relatively rapid and inexpensive, whereas CT scans produce a three-dimensional model (Sittner et al., 2021). However, these methods are not currently suited for detailed mineralogical mapping and/or micron-scale mapping.

In this contribution, we present automated mineralogical scans of 40 cm of drill core from the Au-U Witwatersrand Supergroup, South Africa. The cores intersect approximately 10 cm of the quartzitic footwall and 30 cm of the overlying pyritic conglomeratic reef. The spatial distribution and mode of occurrence of the gold and uranium minerals was accurately recorded at both the macro and micrometer scale. Core scanning by automated mineralogy can be employed when core material is limited, which precludes the preparation of thin sections or milled pulps.