Phosphorus distribution in BIF-derived iron ores of Hamersley Province, Western Australia

The Brockman Iron Formation is one of the most important sources of iron or e in Australia. The usable reserves are Limited, however, by high phosphoru s levels within some of the orebodies. Understanding of the nature and dist ribution of this phosphorus is critical when techniques are being devised t o upgrade the ores for ironmaking. Although some of the phosphorus is prese nt as secondary apatite and other less common phosphates, it has been known for some time that the majority of the phosphorus in Brockman iron ores is associated with goethite, in amounts often exceeding 1%. It has now been s hown that phosphorus levels are dependent not only on the amount of goethit e but also on the microtextural types of goethite in the ore. Extensive mic roanalytical studies of a wide range of ore types have established that the highest phosphorus levels are consistently associated with late-formed col loform goethite in cracks and pore networks. Preliminary studies by scannin g transmision electron microscopy reveal that high phosphorus levels are li mited to goethite composed of ultrafine crystallites. Where dehydration or recrystallization of the goethite has occurred it typically results in expu lsion of the contained phosphorus. The implications of these findings for p hosphorus removal are discussed.