• (a.) Having the two ends modified with unlike planes; -- said of a crystal.
describes doubly terminated crystal with two differently shaped ends.
Hem`i·mor'phic adjective [ Hemi- + Greek ... form.] (Crystallog.) Having the two ends modified with unlike planes; -- said of a crystal. 
hemimorphic A description of crystals that do not have a horizontal axis of symmetry, so that the top and bottom of the crystal display different forms.