COMPARING MINE WASTES IN NEW MEXICO: PHYSICAL AND CHEMICAL PROPERTIES

New Mexico has a rich history of mining operations and has been known to produce various commodities, such as precious metals, raw materials for construction, and coal. The impact of mining on the environment can be measured in a variety of ways. Measuring pH levels of soil and wastes is an effective tool to understand aftermath and provide a way to plan for land reclamation upon closure. This project focuses on mine waste produced by metal and coal mining operations. Mining practices disturb the local environment, creating faults and cracks that can expose reactive minerals like iron sulfides to oxidizing conditions. When exposed to air, water, and bacteria, iron sulfides can react to form acid, which then causes mobilization of heavy metals. The acid and metal solutions can then be transported by water through the environment. Understanding the processes by which acid is produced and transported is critical to planning, operation, and remediation. The implementation of more effective intervention strategies in current and future mines will create safer and more ethical mining practices. In the case of the Blackhawk Mine (Grant County, NM), the impacts of past mining activity on current local acid production and subsequent possible acid mine drainage are unknown. Unlike the Navajo Mine (Fruitland, NM), an active coal mine, acid production is monitored. In order to evaluate these impacts and mitigate potential environmental issues, we analyzed local soil and mine waste from the Blackhawk Mine and coal waste from the Navajo Mine. Paste pH testing of the Black Hawk soil ranged from a low pH of 5.23 to a high of 8.27. Samples were characterized by their bulk geochemistry and pH into one of four categories: Acid-Forming, Non-Acid-Forming, Potential Acid-Forming, and Uncertain Depending on the area and distance from the main shaft, samples varied from slightly acidic to slightly basic. Pyrite, a common Iron Sulfide, has been found in both drill core and hand samples taken from mine waste piles. The presence of pyrite can increase Acid potential, as it is easily oxidized. The presence of pyrite usually indicates copper, native silver, and gold mineral deposits being present. These are the major commodities that were mined when Black Hawk Mine was active, the pyrite was discarded in waste and is still present today. The data suggests a lack of acid generation from the Black Hawk Mine.