The occurrence of Hg, Se, S, Ni, Cr, and Th in Talc Ore: A scanning electron microscopy (SEM) study of historical samples from the Willow Creek Mine, Montana

Due to short timeframes over which small-scale talc mines operate (approximately 1 to 10 years), detailed characterization of their mineralogy and geochemistry in the peer-reviewed literature is limited. Investigation of sample 1497 of the Willow Creek Mine, Montana by scanning electron microscopy using back scatter detection (SEM-BSD) indicates a complex minor mineral assemblage. Hg-Se-S minerals are associated with graphite whereas Zn-Cr-Ni minerals and Th minerals are dispersed in the talc matrix. Notably, Hg, Se, Zn, Cr, and Ni are of human health concern. Minerals with these elements are ~ 20 to 0.4 µm in diameter, and all have examples in the PM₁₀ or PM_2.5 size fraction. These minerals would likely not be separated out during processing of talc ore and would be inhalable. Results indicate a need for detailed SEM-BSD investigations of historic talc products from the Willow Creek Mine and for investigating ore from similar settings in Montana.