[W/K] :: Pyrites

  Pyrite \Pyr"ite\, n.; pl. Pyrites. [Cf. F. pyrite. See
     Pyrites.] (Min.)
     A common mineral of a pale brass-yellow color and brilliant
     metallic luster, crystallizing in the isometric system; iron
     pyrites; iron disulphide.
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           Hence sable coal his massy couch extends,
           And stars of gold the sparkling pyrite blends. --E.
                                                    Darwin.
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  Pyrites \Py*ri"tes\, n. [L., fr. Gr. ?, fr. ? fire. See Pyre.]
     (Min.)
     A name given to a number of metallic minerals, sulphides of
     iron, copper, cobalt, nickel, and tin, of a white or
     yellowish color.
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     Note: The term was originally applied to the mineral pyrite,
           or iron pyrites, in allusion to its giving sparks when
           struck with steel.
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     Arsenical pyrites, arsenopyrite.
  
     Auriferous pyrites. See under Auriferous.
  
     Capillary pyrites, millerite.
  
     Common pyrites, isometric iron disulphide; pyrite.
  
     Hair pyrites, millerite.
  
     Iron pyrites. See Pyrite.
  
     Magnetic pyrites, pyrrhotite.
  
     Tin pyrites, stannite.
  
     White iron pyrites, orthorhombic iron disulphide;
        marcasite. This includes cockscomb pyrites (a variety of
        marcasite, named in allusion to its form), spear pyrites,
        etc.
  
     Yellow pyrites, or Copper pyrites, the sulphide of copper
        and iron; chalcopyrite.
        [1913 Webster] Pyritic

  pyrites
       n : any of various metallic-looking sulfides (of which pyrite is
           the commonest)