Dolomite Calcium Magnesium Carbonate CaMg(CO3)2 In England, dolomite has become a useful source for the production of magnesite by reacting calcined dolomite with sea-water. Dolomite is a double carbonate of calium and magnesium, CaCO3, MgCO3. The mineral was first identified by Count Dolomien in 1791 and named after its discoverer. It is of sedimentary origin and is supposed to have been formed due to chemical action of sea-water containing high percentage of magnesia, on limestone. Theoretically, dolomite contains : CaCO3 : 54.35% MgCO3 : 45.65%