A history of the Questa molybdenum (MOLY) mines, Taos County, New Mexico
The true nature of the molybdenum-bearing veins in Sulphur Gulch (a tributary of the Red River, 8 km east of Questa) was recognized in 1916. Several attempts were made to develop and mine the veins. In 1919, Molybdenum Corp. of America acquired the property and continued development-mining. In 1923, a mill and a camp were built along Red River, and production soared. Ore was extracted by following veinlets down-dip and laterally. Any ore-pockets encountered were stoped, hand-sorted, and the molybdenite was concentrated by flotation. By 1941, the mine extended so deep (260 m) that a mile-long tunnel was driven north from Red River Canyon to connect with the deepest workings. Haulage, drainage, and ventilation costs were greatly reduced. Mining continued down-dip for another 75 m (250 ft) before the high-grade ore ran out. Underground mining ceased in 1958, but exploratory drilling and drifting, begun in 1956, continued. By 1964, a large tonnage of low-grade, open-pitable ore had been delineated just west of the underground mine. The old camp was torn down; a large, modern mill was built on the camp site, and pre-mining stripping began. Openpit mining began in 1965 and continued until 1981. In 1975, exploratory drilling discovered a large orebody beneath the open-pit mine that extended W-SW from the pit. This "deep" ore was developed by vertical shafts and a 2130-m-long (7000 ft), 10-degree decline from the mill to the orebody. Once again the mill was renovated and enlarged, and underground mining began in 1983. The ore is block-caved, hauled up the decline and milled. A soft molybdenum market forced the mine to shut down in 1986. Prices have since improved, and the mine was reopened in 1989. Through 1989, over 190 million pounds of MoS2 have been produced.
- Schilling, John., 1990, A history of the Questa molybdenum (MOLY) mines, Taos County, New Mexico, in: Tectonic development of the southern Sangre de Cristo Mountains, New Mexico, Bauer, Paul W.; Lucas, Spencer G.; Mawer, Christopher K.; McIntosh, William C., New Mexico Geological Society, Guidebook, 41st Field Conference, pp. 381-386.