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Iron Ore Information
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Pure iron is virtually unknown on the surface of the Earth except as
Fe-Ni alloys from meteorites and very rare forms of deep mantle
xenoliths. Therefore, all sources of iron used by human industry exploit
iron oxide minerals, the primary form which is used in industry being
hematite.
However, in some situations, more inferior iron ore sources have been
used by industrialized societies when access to high-grade hematite ore
was not available. This has included utilization of taconite in the
United States, particularly during World War II, and goethite or bog ore
used during the American Revolution and the Napoleonic wars. Magnetite
is often used because it is magnetic and hence easily liberated from the
gangue minerals.
Inferior sources of iron ore generally require beneficiation. Due to the
high density of hematite relative to silicates, beneficiation usually
involves a combination of crushing and milling as well as heavy liquid
separation. This is achieved by passing the finely crushed ore over a
bath of solution containing betonies or other agent which increases the
density of the solution. When the density of the solution is properly
calibrated, the hematite will sink and the silicate mineral fragments
will float and can be removed.
Iron ore mining methods vary by the type of ore being mined. There are
four main types of iron ore deposits worked currently, depending on the
mineralogy and geology of the ore deposits. These are magnetite,
titan magnetite, massive hematite and histolytic ironstone deposits.