See also:mineral consisting of 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 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 .
See also:Wolframite crystallizes in the
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-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 tungsten was first recognized in 1785 by two
See also:brothers, J . J. and F. d'Elhuyar . At the
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 tin-ores, as in many parts of
See also:Cornwall, 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 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 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, Conn., where it has been
See also:mined, and at Monroe, Conn., where it accompanies
See also:bismuth ores . Other localities are in
See also:county, N.C., and in the
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 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 Rudolph Ferber . The
See also:original hiibnerite came from the Mammoth district, Nevada, and the ferberite from the Sierra Almagrera in Spain . It is possible that such minerals may represent the extreme terms in the series formed by the varieties of wolframite .
(F . W .
WOLFRAM VON ESCHENBACH
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