Sabina Bergelt, BSc
S. Bergelt1, C. Yakymchuk1, J. Hanley2, M. Kerr2
1Department of Earth and Environmental Science, University of Waterloo,Waterloo, Ontario, Canada
2Department of Earth Science, Saint Mary's University, Halifax, Nova Scotia, Canada
Graphite is a critical mineral due to its high supply risk and its importance in green-energy technologies, notably being used as the anode in rechargeable lithium-ion batteries. The southwestern Grenville Province contains many natural flake graphite occurrences and showings in both metacarbonate and metasilicate host rocks. However, it is unclear which host rock contains graphite with properties more amenable for downstream battery manufacturing. Properties of natural flake graphite that make it optimal for battery manufacturing include: (i) high crystallinity, (ii) large flake size, and (iii) an absence of microscopic and atomic substitutions. High crystallinity and lack of inclusions are important for conductivity whereas large flake size is better for effective beneficiation. Here, we evaluate if metacarbonate host rocks contain higher-quality graphite compared with graphite hosted by metasilicate rocks. Both rock types are current prospects for graphite exploration and mining, but it is unclear which one, is preferable for battery applications We use a combination of optical microscopy and scanning electron microscopy to quantify graphite flake size and inclusion impurities and transmission electron microscopy to characterize atomic (i.e. substitution) impurities. Raman spectroscopy is used to study the crystallinity of the graphite. In general, graphite hosted by metacarbonate rocks is more consistently of a higher crystallinity with fewer microscale inclusions. Although both carbonate-hosted and metasilicate-hosted graphite have potential for downstream battery manufacturing, flake graphite hosted by metacarbonate rocks appears to be superior. We suggest that host rocks should be an important consideration when prospecting for flake graphite to be used in rechargeable battery manufacturing.