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WOLFRAMITE, or WOLFRAM
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See also:WOLFRAMITE, or WOLFRAM , a See also:mineral consisting of See also:iron-See also:manganese tungstate, (Fe, Mn)WO4. The name is of doubtful origin, but it has been assumed that it is derived from the See also:German See also:Wolf and Rahm (froth), corresponding with the spuma lupi of old writers, a See also:term hardly appropriate, however, to the mineral in question. Wolframite crystallizes in the See also:monoclinic See also:system, with approximation to an orthorhombic type; and the crystals offer perfect pinacoidal cleavage. The See also:colour of wolframite is generally dark brownish-See also:black, the lustre metallic or adamantine, the hardness 5 to 5.5, and the specific gravity 7.1 to 7.5. Wolframite may be regarded as an isomorphous mixture, in variable ratio, of iron and manganese tungstates, sometimes with a small proportion of niobic and tantalic acids. It was in wolframite that the See also:metal See also:tungsten was first recognized in 1785 by two See also:brothers, J. J. and F. d'Elhuyar. At the See also:present See also:time the mineral is used in the manufacture of tungsten-See also:steel and in the preparation of certain tungstates. Wolframite is commonly associated with See also:tin-ores, as in many parts of See also:Cornwall, See also:Saxony and Bohemia. In consequence of the two minerals, cassiterite and wolframite, having nearly the same See also:density, their separation becomes difficult by the See also:ordinary processes of ore-dressing, but may be effected by means of magnetic separators, the wolf ramite being attracted by powerful magnets. A See also:process introduced many years ago by R. Oxland consisted in roasting the mixed ore with carbonate of soda, when the wolfram was converted into See also:sodium tungstate, which was easily removed as a soluble See also:salt. Wolf ramite occurs at many localities in the See also:United States, notably at See also:Trumbull, See also:Conn., where it has been See also:mined, and at See also:Monroe, Conn., where it accompanies See also:bismuth ores. Other localities are in See also:Mecklenburg See also:county, N.C., and in the See also:Mammoth See also:mining See also:district, See also:Nevada. Wolframite has in some cases resulted from the alteration of See also:scheelite (q.v.), though on the contrary pseudomorphs are known in which scheelite has taken the See also:form of wolframite. By oxidation wolframite may become encrusted with tungstic ochre, or tungstite, sometimes known as wolframine, a name to be carefully distinguished from wolf ramite. As the relative proportions of iron and manganese vary in wolframite, the See also:composition tends towards that of other minerals. Thus there is a manganous tungstate (MnWO4) known as hi bnerite, a name given by E. N. Riotte, in 1865, in compliment to Adolph Hiibner, a Saxon mineralogist. There is also a mineral which contains little more than ferrous tungstate (FeWO4), and is known as ferberite, having been named by A. Breithaupt in 1863 after See also:Rudolph Ferber. The See also:original hiibnerite came from the Mammoth district, Nevada, and the ferberite from the Sierra Almagrera in See also:Spain. It is possible that such minerals may represent the extreme terms in the See also:series formed by the varieties of wolframite. (F. W. Additional information and CommentsThere are no comments yet for this article.
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