The Collaborative International Dictionary of English v.0.48:

Pyrgom \Pyr"gom\, n. [Gr. ? a place furnished with towers, fr. ?
   a tower.] (Min.)
   A variety of pyroxene; -- called also fassaite.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Fassaite \Fas"sa*ite\, n. (Min.)
   A variety of pyroxene, from the valley of Fassa, in the
   Tyrol.
   [1913 Webster]