The principal iron ore minerals are MAGNETITE, HEMATITE, GOETHITE and LIMONITE.

For a good description of the various ores, their production and consumption, their depletion and their smelting - click here.

Magnetite ores differ in several ways from hematite ores. Hematite ores generally grade about 60% iron (as Fe₂O₃) and are usually crushed to golf-ball sized lumps in order to facilitate handling and sold with no further processing other than blending with different ores to achieve desired iron and impurity levels. Magnetite ores on the other hand usually grade between 20% and 35% iron (as Fe₃O₄) and require processing to increase the iron concentration to above 64% by weight in order to be saleable.

Australian iron ore production is dominated by hematite and hematite-goethite ores. Two main reasons for this are that Australia is well endowed with hematite ores and the reduced processing requirements mean far less capital intensive equipment is required to produce a saleable product than is required to process magnetite ore for sale as concentrates.

However, concentrates produced from magnetite ores typically have Fe grades higher than 64% by weight, and usually are low in: silica, phosphorous, aluminium and titanium and demand a premium price. It is possible that premium products will also remain saleable in preference to lower quality products in periods of market downturns.

One of the principal costs involved in producing an iron concentrate is determined by the particle size to which the ore must be crushed and ground in order to liberate the iron particles. Many magnetite ores require grinding to 75 micron or lower before a concentrate of suitable grade for sale can be achieved. The degree to which an ore must be crushed or ground impacts costs in several ways. Firstly, grinding is expensive. Secondly, the coarser the concentrate product the easier and cheaper it is to transport. Thirdly, larger waste particles will require less agglomeration if used as back-fill for mine-site rehabilitation.

Whilst the resultant Fe concentrate will ultimately require fine grinding to a particle size suitable for its end use, there are substantial cost savings if the waste material is discarded before grinding.