THE RARE METALS 2<)<> 



dikes ami t he adjacent granites. In Canada it is often associated 

 with granites, and also appears in veins cutting limestone. 

 .1. \\ . \\Vlls has observed molybdenite in pyroxenite, as though 

 produced ly contact metamorphism. 



Geographical Distribution. Molybdenum ores are found in 

 small quantities in the northern Appalachian belt; in the Cordil- 

 leras, especially in Utah; in the Pacific Coast belt, in California 

 and Washington; in Canada and Newfoundland. 



Geological Horizon. The ores seem to be more abundant in 

 the pre-Cambrian, Cambrian and Ordovician terranes, but the 

 Devonian granites sometimes carry molybdenite. 



Method of Reduction. Molybdenum may be reduced to the 

 elemental state by the action of nascent hydrogen upon the 

 oxide or chloride. 



Uses. Molybdenum is used in the manufacture of several 

 important alloys, and in tool steel. It renders steel hard and 

 tough. It is used in the manufacture of chemical salts, the most 

 important of which is ammonium molybdate, used largely to 

 determine the presence of phosphorus in iron ores and in steel. 

 Molybdenum is used as a fire-proofing material, as a germicide, 

 and as a disinfectant. Sodium molybdate is used to color 

 pottery and porcelain blue, and to dye silks and woolens. Molyb- 

 denum tannate is used to color leather, and molybdenum indigo 

 to color india-rubber. 



The production of molybdenum in the United States is small. 

 Ordinary years furnish about 50 tons of molybdenite, containing 

 92 per cent, of the sulphide, MoS 2 . 



Tungsten 



Properties. Tungsten, symbol W, is one of the acid-forming 

 heavy metals. It is closely allied with molybdenum, and is in 

 the same elementary group with chromium. Its melting point 

 is 1700 C.; its specific gravity is 19.1, and its atomic weight is 

 184. 



Ores of Tungsten. The ores of tungsten are not numerous. 

 They are mostly tungstates of the metals. The tungstate of 

 calcium, scheelite, and tungstite, the oxide, are important. 



Wolframite, (Fe,Mn)WO 4 , is the most important among the 

 tungstates of the metals; Hiibnerite, MnWO4, is a tungstate of 

 manganese; reinite, FeWO 4 ; stolzite, PbWO 4 ; cuprotungstite, Cu- 

 WO 4 ; scheelite, CaWO 4 , and tungstite, W0 3 . 



