Dolomite

Dolomite, common mineral with the formula CaMg (CO₃)₂, found chiefly in rock masses as dolomitic limestone, but occurring sometimes in veins. It has a hardness of 3.5 to 4 and a relative density of 2.85. Dolomite crystallizes in the hexagonal system. It is usually colourless, white, or pink, but may be brown, black, or green, depending on the impurities present. When treated with sulphuric acid, dolomite yields calcium sulphate (gypsum) and magnesium sulphate (Epsom salts). Calcined (heated) dolomite is extensively employed as a lining for Bessemer converters in the production of steel from pig iron.

Some varieties of dolomite are called bitter spar or pearlspar. The name dolomite is sometimes given to any rock composed mainly of massive dolomite, or of any combination of magnesium and calcium carbonates.