Serpentinization

An example of serpentinization in olivine (a mineral rich in iron and magnesium) is a geologic source of hydrogen, is:

Fe₂SiO₄ + 2 H₂O –> 2 Fe₃O₄ + 3 SiO₂ + 2 H₂

Fayalite + Water –> Magnetite + Silica + Hydrogen