Serpentinite

Serpentinite is a rock composed of one or more serpentine minerals. Minerals in this group are formed by serpentinization, a hydration andmetamorphic transformation of ultramafic rock from the Earth's mantle.Serpentinization is a geological low-temperature metamorphic process involving heat and water in which low-silica mafic and ultramafic rocks are oxidized and hydrolyzed with water into serpentinite. Peridotite, including dunite, at and near the seafloor and in mountain belts is converted to serpentine, brucite, magnetite, and other minerals -- some rare, such as awaruite, and even native iron.