Geologic map of the Gabbs magnesite and brucite deposits, Nye County, Nevada

During World War II the magnesite deposits at Gabbs, in northwestern Nye County, Nevada, were the source of ore for the world's largest magnesium metal plant.  This Government-owned plant, located at Henderson, near Las Vegas, Nevada, close to the source of power at Boulder Dam, produced 81,272 tons of metal from 920,000 tons of ore during the period September 1942 to November 1944.  Owing to the oversupply of magnesium toward the end of the war, mine production as a source for magnesium metal was curtailed and was finally stopped in November 1944.  As of January 1947, 241,000 tons of magnesite from this area had been used in the production of refractories and oxychloride cement.  Brucite deposits associated with the magnesite have been mined almost continuously since 1935 and had yielded 246,000 tons of ore through January 1945 for use in the refractoies industry of Ohio.