SI U'HATKS, CIIKOMATES, ETC. 



in pegmatites, associated with cassiterite, as in ( 'ornwall, Kngland ; 

 in the Black Hills. South Dakota; also in the Seward IViiin.-ula, 

 Alaska. hi all such cases their origin, like that of the caiterite. 

 is due to piieuniatolitic agencies. A third but le>- coimuoii occur- 

 rence is the replacement in limestone, as at Turnlmll, Connecticut. 



Wolframite and hiilmerite occur in numerous localities in the 

 Western states, associated with gold-bearing quartz veins, but al- 

 ways in small amounts. Wolframite is mined on a commercial 

 scale in Moulder County, Colo- 

 rado. Hiibnerite was first de- 

 scribed or obtained from the 

 Knterprise mine, Nevada, where 

 it is associated in a vein with 

 apatite, fluorite, and scheelite. 



Commercially wolframite is 

 the principal source of the metal 

 tungsten and its salts. The 

 metal is added to steel in the 

 form of ferrotungsten, produc- 

 ing a tungsten steel which will 

 retain its temper when working 

 at or near a red heat ; from this 

 steel, lathe tools, drills, hack 

 saws, etc., are manufactured. 

 Incandescent lamp filaments 

 made of tungsten yield a very 

 white light and reduce the cur- 

 rent used to 1 j watts per candle 

 power, while the carbon fila- 

 ment requires three watts. Sodium tungstate is used in fireproof- 

 ing curtains and draperies ; as a mordant in dyeing. Calcium tung- 

 state is the phosphorescent salt with which the screen used in 

 viewing the Rontgen rays is coated. 



Artificial wolframite may be produced by fusing sodium tung- 

 state and the chlorides of sodium, manganese, and iron. When the 

 iron is left out, hiibnerite is the result. 



FIG. 522. Wolframite Crystal from 

 Zinnwald, Bohemia. 



SCHEELITE 



Scheelite. Calcium tungstate, CaWO 4 ; CaO = 19.4, WO 3 

 = 80.6; Tetragonal; Type, Tetragonal Equatorial ; c = 1.5356; 



