TRANSMISSION ELECTRON MICROSCOPY INVESTIGATION OF MINE WASTE SAMPLES FROM TONOPAH, NEVADA

The first transmission electron microscopy (TEM) study of mine waste from Tonopah, Nevada has revealed several substances of environmental and human health concern. Tonopah was the location of numerous mines throughout the twentieth century, producing mainly silver and lesser amounts of gold. The mines have been inactive since the early 1980’s, and piles of waste varying in particle size from fine clay to large rocks currently remain around the town, exposed to the environment and potentially interact with Tonopah’s citizens. This waste is dominated by clay-sized material and has not been studied extensively. Preliminary X-ray Fluorescence and SEM data from our research group indicates that metals of environmental concern are present, however the clay-sized fraction of the material is poorly understood. This TEM investigation offers findings that confirm the results of our group’s other studies, including the presence of heavy metals. Significant amounts of pyrite were present in one sample, some particles containing trace amounts of arsenic and many containing trace amounts of gold. Iron oxyhydroxides were also found, mainly in the form of goethite. These have high potential for metal absorption, many of which in these samples included lead, chromium, manganese, zinc, and molybdenum. Other substances included potassium feldspar, illite, sericite, manganese oxides, and amphiboles. The preliminary TEM data suggests that fine particulate matter (PM_2.5 size range) from the mine waste in Tonopah may be of broad environmental and human health concern as the materials found can be easily transported by natural pathways, especially through the air. Because these particles are so fine, there is a possibility of deep lung penetration which could cause irritation and damage to the tissues. Due to the specific elements found in the waste, inhalation of fine particles could also lead to adverse health effects.