Source : Webster's Revised Unabridged Dictionary (1913)

Amphibole \Am"phi*bole\ ([a^]m"f[i^]*b[=o]l), n. [Gr.
   'amfi`bolos doubtful, equivocal, fr. 'amfiba`llein to throw
   round, to doubt: cf. F. amphibole. Ha["u]y so named the genus
   from the great variety of color and composition assumed by
   the mineral.] (Min.)
   A common mineral embracing many varieties varying in color
   and in composition. It occurs in monoclinic crystals; also
   massive, generally with fibrous or columnar structure. The
   color varies from white to gray, green, brown, and black. It
   is a silicate of magnesium and calcium, with usually
   aluminium and iron. Some common varieties are {tremolite},
   {actinolite}, {asbestus}, {edenite}, {hornblende} (the last
   name being also used as a general term for the whole
   species). Amphibole is a constituent of many crystalline
   rocks, as syenite, diorite, most varieties of trachyte, etc.
   See {Hornblende}.

Source : WordNet®

amphibole
     n : a mineral or mineral variety belonging to the amphibole
         group