Formation
(1) Secondary hydrothermal, through alteration of ultramafic rocks, particularly during the serpentinization of olivine and pyroxene under low-temperature (often < 300 °C), strongly alkaline conditions (e.g., in ophiolites). (2) As a product of contact metamorphism of dolomitic limestones through the thermal decomposition (decarbonation) of dolomite with later influx of H₂O-rich fluids, with periclase (MgO) and calcite (CaCO₃) as intermediate phases.
