Platinum also exists in small quantities in streams in the neighbourhood of the Blue Mountains, eastern Oregon, where the Powder River Gold Dredging Co., in Sumpter district, produces on a small scale. Other platiniferous localities in eastern Oregon are the Granite and Canyon districts, and Spanish Gulch in Wheeler county[10] p. 541. _Colorado._—Platinum is known to exist in the black sands from Clear Creek. Its presence has also been reported in the gold gravels of the Iron Hill placer at Como, where it occurs mechanically combined with magnetite. Another occurrence recently discovered is in a vein worked by the Rollcall Mining Co., near Villa Grove. An assay of material from this vein, taken at a depth of 1,500 ft., showed the following values: gold, 3·2 oz.; platinum, 5·09 oz.; silver, 3·05 oz.; and copper, 3·5 per cent.[9] p. 592. _Nevada._—In 1909 the occurrence of platinum in Clark county was noticed by the United States Geological Survey to be in association with copper, nickel and cobalt ores from the Key West and Great Eastern Mines, near Bunkerville. The ore bodies are contained in pegmatites and basic intrusions, which carry pyrrhotite and chalcopyrite, the platinum content in the ore averaging about 0·2 oz. per ton[72]. In 1914 platinum, with palladium, was discovered at the Boss Gold Mine, situated 10 miles west of Goodsprings, in Clark county. The mine was originally worked for copper, and later for its copper and gold contents. The country rock consists of limestone of middle Carboniferous age, intruded by sills of quartz monzonite porphyry, the ore bodies occurring in a fault zone in the limestone. The copper ores comprise mainly chrysocolla and malachite, and contain traces only of platinum. The gold ore occurs in a fine-grained siliceous matrix, containing a bismuth-bearing variety of _plumbo-jarosite_ (a hydrous sulphate of iron and lead). The rare metals are present in the free state, being apparently alloys of gold, platinum and palladium[73]. In 1919 the Boss Mine shipped $22,365 worth of platinum-bearing ore[74]. A plant of 300 tons monthly capacity has recently been erected at Los Angeles, California, for the treatment of its complex ores, which average 7 per cent. of copper, 4 per cent. bismuth, and 1·0 oz. of platinum and palladium, 0·75 oz. of gold, and 3 oz. of silver per ton. The pulp from ore pulverized to 80 mesh is agitated with sulphuric acid (2 per cent.). The acid solution contains the copper and about 20 per cent. of the platinum. The copper is precipitated as cement copper, together with the platinum, by means of scrap-iron. The remainder of the platinum, together with the gold and silver, is first leached with, and then precipitated from, a neutral solution of calcium chloride. The inventors of the process claim that approximately 92 per cent. of the copper, 96 per cent. of the platinum metals, gold and silver, and over 90 per cent. of the bismuth are recovered by this process[75].