Iron is the fourth most abundant rock-forming element and composes about 5% of the Earth’s crust. Astrophysical and seismic evidence indicate that iron is even more abundant in the interior of the Earth and has apparently combined with nickel to make up the bulk of the planet’s core. Geologic processes have concentrated a small fraction of the crustal iron into deposits that contain as much as 70% of the element. Pure iron is virtually unknown on the surface of the Earth except as Fe-Ni alloys from meteorites. Therefore, all sources of iron used by human industry exploit iron oxide or iron carbonate minerals. An estimated 98% of the ore shipped in the world is consumed in the manufacture of iron and steel. The remaining 2% is used in the manufacture of cement, heavy-medium materials, pigments, ballast, agricultural products, or specialty chemicals. As a result, demand for iron ore is tied directly to the production of raw steel and the availability of high-quality ferrous scrap.
Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in colour from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite, limonite or siderite (FeCO3). Iron ore is the raw material used to make pig iron, the main raw material in steel.
Magnetite (“lodestone”) is beneficiated by crushing and then separating the magnetite from the gangue minerals with a magnet. This is usually so efficient that lower grade ore can be treated when it is magnetite than a comparable grade of hematite ore, especially when the magnetite is quite coarse.
Iron is the world’s most commonly used metal. It is used primarily in structural engineering applications and in maritime purposes, automobiles, and general industrial applications (machinery).
Iron-rich rocks are common worldwide, but ore-grade commercial mining operations are dominated by China, Brazil and Australia. The major constraint to economics for iron ore deposits is not necessarily the grade or size of the deposits but the position of the iron ore relative to market
World production averages over one billion metric tons of raw ore annually. The world’s largest producer of iron ore is the Brazilian mining corporation Cia. Vale do Rio Doce (“Vale”, formerly CVRD), followed by Australian company BHP Billiton and the Anglo-Australian Rio Tinto Group. These three companies controlled 75% of seaborne iron ore exports in 2006.
The Marcona Mine, owned by the Shougang Group of China and operated by Shougang Hierro Peru S.A.A., is the only current significant producer of iron ore in Perú. With a total resource base of about 1.5 Gt, the mine, located near Nazca, Ica, outputs about 6 Mt of product per year, 90% of that comprising a variety of pellets.
China is currently the largest consumer of iron ore, which translates to be the world’s largest steel producing country. China is followed by Japan and Korea, which consume a significant amount of raw iron ore and metallurgical coal. India is also a large producer of steel though until recently much of their demand has been filled by domestic production.
There are several types of iron ore including lump, fines concentrates and pellets:
IRON ORE LUMP
Lump ore is relatively unprocessed apart from crushing to produce a product with an average size of 6 mm to 30 mm. Lump ore with a high iron and low impurity content, coupled with a high strength at high temperature is considered to be a premium product.
IRON ORE FINES
Iron ore fines can be defined as material less than 6.3 mm in size and are generated during the crushing and screening of crude iron ore. Natural fines should contain between 10% and 15% below 150 microns in size. Fines have traditionally been used as feedstock for sinter, which is in turn added to blast furnaces to produce pig iron. Fines account for 60% of the world-wide iron ore trade.
IRON ORE CONCENTRATES
Concentrates are iron ore products that have undergone significant processing, generally including grinding to less than 1mm in size followed by various techniques to separate the iron from the impurities contained in the crude ore. Concentrates may be blended with fines or sinter feed if they are coarse enough.
IRON ORE PELLETS
Pellets are produced by agglomerating a very fine-sized iron ore concentrate and a binder, such as bentonite. Pellets are usually between 9mm and 16mm in size. Because of its consistency of grade and size, pellets sell for a premium over lump ore. The 2006 contract price for Brazilian pellets in Europe was $US112.00 per tonne.