MINE WASTE AS A POTENTIAL RESOURCE

The United States has an extensive mining history, and the mining and processing of metallic mineral deposits have created large amounts of waste as byproducts. Mine wastes were deemed unvalued materials at the time, were collected in dumps, leach piles, tailings, etc. However, changes in mineral processing technology, market demand, commodity prices, and geopolitical issues may transform what was formerly discarded as wastes into materials with the potential to be economically remined to recover additional resources. Therefore, mine waste is an excellent example of an unconventional resource that may be reevaluated for numerous commodities, including critical minerals.

One approach for considering mine waste as a resource is to investigate mining operations that had significant past production of base metals, because some of these deposits can contain significant unrecovered endowments of critical minerals, such as As, barite, Bi, Ga, Ge, In, PGEs, Sb, Sn, and Te. For example, the Santa Rita porphyry Cu deposit at Chino, New Mexico, has been evaluated for indium in the past, so there may be significant quantities of indium in the waste at that deposit. Similarly, the Bingham porphyry Cu deposit has recently begun producing Te, suggesting that there may be significant quantities of Te in mine waste there.

A significant obstacle to evaluating mine wastes as potential resources of critical minerals on a national scale is the lack of comprehensive information on the location and scale of mine waste sites in the United States, and scant analyses of the concentrations of commodities in that waste. As part of the Infrastructure Investment and Jobs Act of 2021, the Earth Mapping Resources Initiative of the U.S. Geological Survey is funding the USMIN project to develop a comprehensive and authoritative national inventory of mine waste features. The USMIN team will work with collaborators from State and Federal agencies to populate this database, which will include information on the deposit type, geology, and mineralogy of the parent mineral deposit.