Dolomite is a carbonate mineral consisting of a mixed calcium-magnesium carbonate, CaCO3.MgCO3, crystallizing in the rhombohedral system. It is usually white or colorless. The term is also used to denote a rock with a high ratio of magnesium to calcium carbonate. Dolomite is often found associated with limestone or marble and in magnesium-rich metamorphic rocks. Dolomitic limestone is a rock in which the limestone has been partially replaced by dolomite.
Dolomite is used as an ornamental and building stone, and is a source of magnesium. Hardness 3.5–4, relative density 2.8.