Source : Webster's Revised Unabridged Dictionary (1913)

Cordierite \Cor"di*er*ite\ (k?r"d?-?r-?t), n. [Named after the
   geologist Cordier.] (Min.)
   See {Iolite}.

Source : WordNet®

cordierite
     n : a blue mineral of magnesium and iron and aluminum and
         silicon and oxygen; often used as a gemstone