Source : Webster's Revised Unabridged Dictionary (1913)

Dolomite \Dol"o*mite\, n. [After the French geologist Dolomieu.]
   (Geol. & Min.)
   A mineral consisting of the carbonate of lime and magnesia in
   varying proportions. It occurs in distinct crystals, and in
   extensive beds as a compact limestone, often crystalline
   granular, either white or clouded. It includes much of the
   common white marble. Also called {bitter spar}.

Source : WordNet®

dolomite
     n 1: a kind of sedimentary rock resembling limestone but
          consisting almost entirely of the mineral dolomite
     2: a light colored mineral consisting of calcium magnesium
        carbonate; a source of magnesium; used as a ceramic and as
        fertilizer