Before revision: 276x276px|Ferromanganese nodules found on the seafloor Ferromanganese nodules are mineral concretions comprised of silicates and insoluble iron and manganese oxides that form on the ocean seafloor and terrestrial soils.
After revision: 276x276px|Ferromanganese nodules found on the seafloor Ferromanganese nodules are mineral concretions composed of silicates and insoluble iron and manganese oxides that form on the ocean seafloor and terrestrial soils.