Description: Abstract: The tungsten deposits of the Nightingale district are just within the western border of Pershing County, Nev., and in the Nightingale or Truckee Range, which lies east of Winnemucca Lake. The Tertiary volcanic rocks of the district rest unconformably upon intrusive granodiorite and steeply dipping metamorphosed limestones and slates of unknown age. The tungsten deposits are of the contact-metamorphic type: The ore consists of scheelite bearing tactite, a dark silicate rock that was formed by metamorphism of limestone at the granodiorite contact. Scheelite (calcium tungstate) is the only valuable mineral. The gangue minerals are epidote, quartz, pyroxene, garnet, calcite, tremolite, molybdenite, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, apatite, and sphene. The bodies of tactite are generally tabular, and they extend downward steeply, because both the limestones and the granodiorite contact dip vertically or nearly so. The largest tactite body of the district is at the Nightingale mine; it attains a maximum thickness of 60 feet and is nearly a thousand feet long, but only for part of its length is it thick enough and rich enough to be potentially minable. That it continues downward below the mine workings, which extend to a depth of 128 feet, is shown by nine drill holes put down by the Bureau of Mines, United States Department of the Interior, in 1940, all of which encountered tactite at depths of, 260 to 350 feet. The mine has produced about 12,000 tons of ore, and its ore bodies contain the principal reserve of the district. In 1938 the reserves of the entire district were estimated to be about 50,000 tons of ore averaging between 0.25 and 0.50 percent of W03. Later diamond drilling by the Bureau of Mines indicated that the principal tactite body continues to at least twice the depth hitherto explored by the mine workings.
Creator: Smith, Ward C. & Guild, Philip White
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