Carbonate, MgCO₃ and end-member of a solid solution series with siderite, FeCo₃; sp. gr. 3.0; hardness 4; whitish; earthy lustre; compact or granular; occurs as an alteration product of serpentines, dolomites, or limestones and may form as a chemical precipitate. It is mined commercially and used in the production of magnesium compounds, refractory products, and special cements.