PRELIMINARY RESULTS FROM A CRITICAL MINERALS CHARACTERIZATION OF TUNGSTEN QUEEN MINE TAILINGS, VANCE COUNTY, NORTH CAROLINA

The Tungsten Queen mine in Vance County, North Carolina, produced over 1,000,000 STU WO₃ while in operation from 1943 to 1971. Located in the Hamme Tungsten Mining District, an S-R-V tungsten deposit in the Porphyry Cu-Mo-Au mineral system, the mine contains an estimated 2,000,000 tons of tailings over ~19 ha. The NC Geological Survey is characterizing the Tungsten Queen tailings as part of a USGS-funded Earth Mapping Resources Initiative project to determine if they are a potential source for the critical minerals W, Bi, Mn, and Sc. The study also includes a cursory evaluation of the potential for acid production from the tailings, given the mine’s proximity to a local drinking water reservoir.

Three types of samples were collected from privately-owned portions of the Tungsten Queen tailings ponds: 1) eight near-surface composite samples representing an average composition of each designated area; 2) four near-surface grab samples and two grab sample profiles from locations of scientific interest; and 3) seven sonic cores composited over one-foot intervals. Composite and near-surface grab sample data suggest tailings collected from the large southern tailings pond have the highest concentrations of W and Bi. Here, W is most abundant in the central and southeastern areas, while Bi is highest in the southeastern portion. Mn is highest in two grab samples, one from the northern tailings pond and one from the southern, which were collected from near-surface layers with abundant dark minerals. Otherwise, Mn is highest in the northern and southeastern portions of the large southern pond. Scandium was mostly below the detection limit. In-depth geochemical modeling is planned once the drill core data are received from the lab.

Acid-base accounting provides a cursory evaluation of the potential for acid production from the Tungsten Queen tailings. Net Neutralization Potential values for composite samples (-3.32 to -0.86 ‰) and grab samples (-6.14 to 0.49 ‰) fall within a range of uncertainty where more tests may be needed. Composite sample Neutralization Potential Ratio (NPR) data vary from 0.13 to 0.58, values which are considered to be acid producing. Meanwhile most grab sample NPR values fall between -8.96 and 0.9 indicating they are acid producing, while one sample has an NPR of 2.56, which is interpreted as non-acid producing.