The Collaborative International Dictionary of English v.0.48:

Halometer \Ha*lom"e*ter\ (h[.a]*l[o^]m"[-e]*t[~e]r), n. [Gr.
   "a`ls, "alo`s, salt + -meter.]
   An instrument for measuring the forms and angles of salts and
   crystals; a goniometer.
   [1913 Webster]