Fortescue has been trying to grow margins with a new, higher grade product. : A unit of Fortescue Metals Group and its Taiwanese partner, Formosa Steel IB, will spend about $US2.6 billion ($3.7 billion) to develop the second stage of a magnetite iron ore project in Western Australia. FMG Iron Bridge, in which the world's fourth-largest iron ore miner holds an 88 per cent stake, will invest a total of $US2.1 billion on the project.