Before revision: 276x276px|Ferromanganese nodules found on the seafloor Ferromanganese nodules (FMN) form in the oxidizing environment of the abyssal pelagic zone .
After 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 .