Dolostone is a sedimentary rock in the class known as chemical sedimentary rocks. It is closely related to limestone, but includes magnesium in the form of calcium-magnesium carbonate. The main constituent is the mineral dolomite, CaMg(CO3)3. The main pathway to the formation of dolostone is thought to be the replacement of some of the calcium in limestone with magnesium. Dolostone deposits are mainly ancient rocks, giving time for the replacement process in limestone.
Lutgens and Tarbuck