The Collaborative International Dictionary of English v.0.48:

Rhodochrosite \Rho`do*chro"site\, n. [Gr. "ro`don the rose + ???
   a coloring.] (Min.)
   Manganese carbonate, a rose-red mineral sometimes occuring
   crystallized, but generally massive with rhombohedral
   cleavage like calcite; -- called also dialogite.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rhodochrosite
    n 1: a mineral consisting of manganese carbonate; a source of
         manganese