serpentinization

thumb|Chromite|Chromitic [[serpentinite from Styria Province, Austria]] Serpentinization is a hydration and metamorphic transformation of ferromagnesian minerals, such as olivine and pyroxene, in mafic and ultramafic rock to produce serpentinite. Minerals formed by serpentinization include the serpentine group minerals (antigorite, lizardite, chrysotile), brucite, talc, Ni-Fe alloys, and magnetite. The mineral alteration is particularly important at the sea floor at tectonic plate boundaries.

== Formation and petrology == thumb|Serpentinite partially made of [[chrysotile, from Dobšiná, Slovakia]] Serpentinization is a form of low-temperature (0 to ~600 °C) metamorphism of ferromagnesian minerals in mafic and ultramafic rocks, such as dunite, harzburgite, or lherzolite. These are rocks low in silica and composed mostly of olivine (), pyroxene (), and chromite (approximately ). Serpentinization is driven largely by hydration and oxidation of olivine and pyroxene to serpentine group minerals (antigorite, lizardite, and chrysotile), brucite (), talc (), and magnetite (). Under the unusual chemical conditions accompanying serpentinization, water is the oxidizing agent, and is itself reduced to hydrogen, . This leads to further reactions that produce rare iron group native element minerals, such as awaruite () and native iron; methane and other hydrocarbon compounds; and hydrogen sulfide.