Mineralogical Characterization of Tailings at the Vermont Asbestos Group Mine, Belvidere Mountain, Northern Vermont

Chrysotile asbestos was mined from serpentinized ultramafic rocks at the Vermont Asbestos Group Mine, located on Belvidere Mountain in the northern part of the state. Mining and milling operations at the site spanned much of the twentieth century and resulted in three waste piles estimated to contain over 70 million tons of tailings. The site has received recent attention because of impacts to downstream wetlands due to erosion of the waste piles, and locally elevated concentrations of Ni, Cr, and As in surface waters.

Detailed geochemical and mineralogical studies of 16 composite samples of mine wastes from the site included bulk geochemistry, optical microscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and Raman spectroscopy. Major-element chemistry showed differences among waste areas for Al, Ca, K, Na, Si, and Ti. Mineral phases determined by XRD and EPMA included serpentine-group minerals, magnetite, chlorite, quartz, olivine (Fo₈₆), pyroxene, and brucite, and locally abundant mica and carbonate minerals. Nickel is present in magnetite, olivine, and serpentine, with approximately 1, 0.4, and 0.2 wt. % NiO, respectively. XRD was unable to distinguish among the serpentine-group minerals, but Raman spectroscopy was used to differentiate antigorite and chrysotile. Long-count XRD scans of the (110) peak for amphiboles revealed trace amounts of amphibole minerals in 12 of the samples. XRD, EPMA, and Raman spectroscopy were used to identify tremolite in a sample of host rock; examination of tailings by SEM and EPMA found non-asbestiform calcic amphiboles in one sample. This study indicates that chrysotile is a significant component of the near-surface waste piles; amphibole is present in trace amounts in some samples.

To date, no specific human health concerns have been raised. However, mineralogical information from the mine wastes will aid in evaluating potential human-health effects associated with the site.