Manganese is widely distributed in the terrestrial crust. It is usually associated with the iron ores, in relatively small concentrations. The principal manganese ores are pyrolusite (MnO2), psilomelane, manganite (MnO(OH)), braunite (3Mn2O3.MnSiO3) and hausmannite (Mn3O4), that can be found in Brazil, Gabon, India, Ghana, Congo and South Africa. Other manganese ores, although less important, are rhodochrosite (MnCO3) and rhodonite (MnSiO3).