dolomite
Dol"o*mite, n. Etym: [After the French geologist Dolomieu.] (Geol. & Min.) Defn: 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.