HAMME (TUNGSTEN QUEEN) MINE TAILINGS, VANCE COUNTY, NORTH CAROLINA: MINERAL CHEMISTRY OF POTENTIALLY RECOVERABLE HUEBERNITE-WOLFRAMITE AND SULFIDE MINERALS

The Hamme (Tungsten Queen) mine, Vance County, N.C., was worked for wolframite-huebnerite and also produced minor amounts of sulfides (copper and silver). There are about 1 million metric tons of quartz-dominated tailings containing about 0.25% WO₃, with accessory fluorite and very minor sulfides – mostly galena with accessory silver values. Tungsten prices are currently high (~$310/mtu WO₃). This is an outgrowth of a statewide study of mine tailings by the NCSU Minerals Research Laboratory.

This study reports preliminary mineral chemistry of huebnerite, fluorite, and accessory sulfide minerals in the mine’s tailings piles. All minerals investigated have concentrations which show very limited compositional ranges. Huebnerite is strongly enriched in WO₃ (73.5-75.5 wt. %), MnWO₄ (97.3-99.7%, and Mn (1.037-1.065 atoms per formula unit, apfu) but is depleted in Fe²⁺ (0.040-0.029 apfu). Sulfide mineralogy is comprised of chalcopyrite with concentrations of Cu (33.8-38.2 wt. %), Fe (29.7-29.9 wt. %), and S (34.5-34.6 wt. %) and galena with concentrations of Pb (83.0-85.8 wt. %), S (13.2-13.9 wt. %). Lead in Hamme Tungsten deposit is comparable in S concentrations to other deposits; however, Pb concentrations are lower. Hamme tungsten deposit huebnerite compositions reported here are comparable (although slightly enriched in Mn but depleted in Fe²⁺) to other huebnerite deposits such as Round Mountain in Nevada and some huebnerites from Portugal. Compared to other wolframite deposits, the Hamme tungsten deposit is more depleted in Fe²⁺ and highly enriched in MnWO₄, an indication of a lack of the substitution of its Mn by other cations. Potentially economic minerals in the mine’s tailings include wolframite-huebnerite, the quartz ‘sand’ that comprises the bulk of the tailings for specialized applications, fluorite for cement and/or glass manufacture, and potential credits of silver from the galena.