The Collaborative International Dictionary of English v.0.48:

Epigene \Ep"i*gene\, a. [Pref. epi- + Gr. ? to be born, grow.]
   1. (Crystallog.) Foreign; unnatural; unusual; -- said of
      forms of crystals not natural to the substances in which
      they are found.
      [1913 Webster]

   2. (Geol.) Formed originating on the surface of the earth; --
      opposed to hypogene; as, epigene rocks.
      [1913 Webster]