The composition of olivine is mainly a complete isomorphic mixed crystal formed by two end-member components of Mg2SiO4 and Fe2SiO4. In iron-rich members, sometimes a small amount of Ca2+ and Mn2+ replace Fe2+ in them, while magnesium-rich members may have a small amount of Cr3+ and Ni2+ instead of Mg2+. In addition, they may also contain traces of Fe3+, Zn2+, etc.