 Serpentinite – oxidized and hydrolized low-silicon, iron- and magnesium-rich oxide igneous rocks – are progressively weathered through this zone.Ferromagnesian minerals are the principal hosts for nickel, cobalt, copper and zinc in sulfide-poor mafic and ultramafic rocks, and are retained higher in the profile than sulfide-hosted metals.They are leached from the upper horizons and reprecipitate with secondary iron-manganese oxides in the mid- to lower saprolite.