The Collaborative International Dictionary of English v.0.48:

Epidote \Ep"i*dote\, n. [Gr. ? to give besides; ? over + ? to
   give: cf. F. ['e]pidote. So named from the enlargement of the
   base of the primary, in some of the secondary forms.] (Min.)
   A mineral, commonly of a yellowish green (pistachio) color,
   occurring granular, massive, columnar, and in monoclinic
   crystals. It is a silicate of alumina, lime, and oxide of
   iron, or manganese.
   [1913 Webster]

   Note: The Epidote group includes ordinary epidote, zoisite or
         lime epidote, piedmontite or manganese epidote,
         allanite or cerium epidote.
         [1913 Webster]