THE MINERALOGICAL MAKE-UP OF MINE WASTE: INSIGHTS FROM ABANDONED SILVER MINE WASTE PILES

Mining operations produce significant amounts of waste due to the viable ore making up only a relatively small percentage of the total rock material mined from the subsurface. This particular study is focused on evaluating the mineralogical and geochemical characteristics of the abundant mine waste piles located in the mining town of Tonopah, NV. Historical mines, like the silver mine found in Tonopah, have not undergone the same risk management practices as modern-day mining practices have, as documented by the existence of extensive waste piles decades after closure of mining operations.

It is well known that mine waste tailings have the potential to pose serious risks, e.g. in the form of acid mine drainage, if they contain significant concentrations of sulfur, chromium, and other heavy metals. Hence there are naturally concerns associated with the mineralogical and elemental components in the waste that mines produce. This study aims to provide characterization of these waste materials in order to determine whether or not components are toxic to the environment and/or potentially hazardous to human health. By mineralogically characterizing and documenting the presence of heavy metals, and evaluating the degree to which these components exist through the mine waste tailings, this work aims to gain insight into the current nature of the exposed Tonopah mine waste.

Specifically, this project uses ASD spectroscopy, scanning electron microscopy (SEM), and petrographic microscopy in order to analyze and interpret the mineral characteristics and composition of a variety of samples collected from the piles of mine waste that surround the town of Tonopah. It is acknowledged that mine waste is a complex material that is often challenging to understand in scope and size. This project therefore focuses on analyzing the characteristics of the waste at grain size scales that are relevant to assessing the potential risk to both the environment and human health. The impact of these results is likely of both local, regional, and scientific interest as it will provide new insights into the characteristics of untreated mine waste.