A REVIEW OF THE CURRENT UNDERSTANDING OF THE MINERALOGY AND GEOCHEMISTRY OF MINE WASTE FROM TONOPAH, NEVADA: IMPLICATIONS FOR RECYCLING AND ENVIRONMENTAL HEALTH

The first detailed investigation of representative mine wastes from Tonopah, Nevada has revealed substances of environmental and public health concern, as well as potential economic value. Tonopah was the location of several mines throughout the twentieth century, producing mainly silver as well as minor gold. Mining in the area declined by mid-1940’s and ceased in early 1980s. Now an inactive site, piles of waste ranging from fine clay to large boulders remain widely distributed around the town, exposed to arid elements and potentially interact with residents. This waste is dominated by clay-sized material and has not been studied extensively. Comprehensive analyses were conducted to define the nature of the waste, including powder X-ray diffraction, X-ray fluorescence, microscopy (polarizing light, scanning electron, transmission electron), and reflective spectroscopy. The data characterize the waste as high in silicate material, which is consistent with the geology of the region. Heavy metals of concern were also found, including arsenic, lead, chromium, barium, and others that could pose risks to public health. Major inerals observed included silicates, zircon, iron oxyhydroxides, and pyritic material, which often contained heavy metals. Findings were consistent across the analyses performed. These materials could be detected at the micrometer, and sometimes nanoscale. This poses an increased risk as particulate matter under 2.5 microns (PM2.5) that contained elements of environmental health concern were routinely detected. PM2.5 can intrude deep into the lungs, causing damage and increasing the likelihood of toxin introduction into the. Material of economic importance was also found in the waste, such as gold, silver, and electrum. Potential exists for the remediation of the extensive mine waste deposits of Tonopah, supported economically through careful recycling of silver and gold.