Iron ore can be found in the form of several natural forming minerals, these include Hematite (Fe₂O₃), Magnetite (Fe₃O₄), Siderite and Goethite. Iron ore is the main raw material required for steel production. The price at which iron is bought depends greatly on its type and purity.

Iron Ore Samples - 1. Banded magnetite and hematite (BHP); 2. Banded magnetite and hematite (Rio Tinto); 3. Goethitic Channel Iron; 4. Martite (Irvine Island); 5. Coarse specular hematite (Irvine Island); 6. Hematitic Sandstone (Irvine); 7. Hematitic conglomerate (Irvine Island); 8. Hematitic siltstone (Irvine Island)

Hematite

Hematite can be found in large rich deposits generally within banded iron formation (BIF) hosted iron deposits. On Irvine Island, martite is commonly the primary Iron mineral. Martite is hematite replacement of magnetite that retains the octahedral crystal structure of magnetite. Hematite on Irvine Island occurs in high grade intersections grading up to 67.43% Fe (drill hole ID27).

Lower grade hematite ores can be upgraded by beneficiation. Irvine Island iron ore intersections have been proved to be upgradeable using the Wet High Intensity Magnetic Separation (WHIMS) beneficiation technique.

Magnetite

Coarse grained magnetite on Irvine Island has been found at depth below weathered hematite horizons. Magnetite ore is suitable for producing concentrates and can attract a premium price because of superior smelting properties. The properties of Irvine Island magnetite ore have been tested using Low Intensity Magnetic Seaparation (LIMS). The LIMS beneficiation technique has increased product grades dramatically to make a marketable Ore Concentrate.

High grade magnetite intersection from drill hole ID28, Irvine Island.

Siderite

Siderite deposits are usually of low grade ranging from 30 to 35% Fe. The use of siderite is generally low due to the great difficulties in mining, beneficiation and smelting (Zhu 2009).

Goethite

Goethite deposits mainly consist of leaching and residual types, usually capping or resulting from the weathering of an Iron ore body. Channel iron deposits are dominated by goethite forming within historic river channels. Typically Hamersley ores are a combination of martite and goethite. These ore types  account for a major portion of sea borne trade in iron ore (Clout 2005).

Impurities

Many deposits within Western Australia and around the world are hindered by high levels of impurities. The impurities cause problems at refineries, for example high TiO2 levels can affect the sinter RDI (Reduction Degradation Index), requiring the product to be sold at a discount. High levels of alkali metals particularly Na2O can cause scabs on the furnace walls, thus reducing the demand for the product.

Most of the assessed iron ore from Irvine Island has been low in impurities with the exception of silica which is the least critical of all the major impurities.

Clout, J,M, F, Iron Formation-Hosted Iron Ores in the Hamersley. Iron ore Conference Fremantle, WA, 19-21st September 2005.

Zhu, D, Qiu, G, Pan, J, 2006. present situation and future trends in the Chinese steel industry and utilisation of low-grade Iron ore resources, Iron Ore 2009 Proceedings, 27-29 July Perth, pp 35-42.