Anglo-Australian mining giant Rio Tinto said it has reached a milestone by shipping a total of 4 billion tons of iron ore from the Pilbara region in Western Australia to China. The milestone comes 51 years after the first shipment of almost 22,000 tons of Pilbara iron ore was sent from Australia’s Dampier Port to China’s Shanghai No.1 Steel Mill, which has since become part of China Baowu Steel Group, the world’s top steel producer. Four billion tons is enough iron ore to produce the steel needed for about 45,000 Sydney Harbour Bridges, or more than 23,000 Beijing National Stadiums. Rio Tinto …