Webster's English Dictionary

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wolframite

wol.fram.ite \'wu.l-fr*-.mi-t\ n [G wolframit, fr. wolfram] : a mineral 
   (Fe,Mn)WO4 that consists of an iron manganese tungstate  of a usu. brownish 
   or grayish black color and slightly metallic luster, occurs in monoclinic 
   crystals and in granular or columnar masses, and is used as a source of 
   tungsten