Iron ore
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 color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the form of magnetite, hematite, goethite, limonite, or siderite.
Ores containing very high quantities of hematite or magnetite are known as natural ore or direct shipping ore, and can be fed directly into iron-making blast furnaces. Iron ore is the raw material used to make pig iron, which is one of the primary raw materials to make steel — 98% of the mined iron ore is used to make steel. In 2011 the Financial Times quoted Christopher LaFemina, mining analyst at Barclays Capital, saying that iron ore is "more integral to the global economy than any other commodity, except perhaps oil".
Banded iron formations
s are sedimentary rocks containing more than 15% iron composed predominantly of thinly-bedded iron minerals and silica. Banded iron formations occur exclusively in Precambrian rocks, and are commonly weakly-to-intensely metamorphosed. Banded iron formations may contain iron in carbonates or silicates, but in those mined as iron ores, oxides are the principal iron mineral. Banded iron formations are known as taconite within North America.The mining involves moving tremendous amounts of ore and waste. The waste comes in two forms: non-ore bedrock in the mine, and unwanted minerals, which are an intrinsic part of the ore rock itself. The mullock is mined and piled in waste dumps, and the gangue is separated during the beneficiation process and is removed as tailings. Taconite tailings are mostly the mineral quartz, which is chemically inert. This material is stored in large, regulated water settling ponds.
Magnetite ores
The key parameters for magnetite ore being economic are the crystallinity of the magnetite, the grade of the iron within the banded iron formation host rock, and the contaminant elements which exist within the magnetite concentrate. The size and strip ratio of most magnetite resources are irrelevant, as a banded iron formation can be hundreds of meters thick, extend hundreds of kilometers along strike, and can easily come to more than three billion or more tonnes of contained ore.The typical grade of iron at which a magnetite-bearing banded iron formation becomes economic is roughly 25% iron, which can generally yield a 33% to 40% recovery of magnetite by weight, to produce a concentrate grading over 64% iron by weight. The typical magnetite iron ore concentrate has less than 0.1% phosphorus, 3–7% silica, and less than 3% aluminium.
As of 2019, magnetite iron ore is mined in Minnesota and Michigan in the United States, eastern Canada, and northern Sweden. Magnetite-bearing banded iron formation is mined extensively in Brazil as of 2019, which exports significant quantities to Asia, and there is a nascent and large magnetite iron ore industry in Australia.
Direct-shipping (hematite) ores
Direct-shipping iron ore deposits are currently exploited on all continents except Antarctica, with the largest intensity in South America, Australia, and Asia. Most large hematite iron ore deposits are sourced from altered banded iron formations and igneous accumulations.DSO deposits are typically rarer than the magnetite-bearing BIF or other rocks which form their primary source, or protolith rock, but are considerably cheaper to mine and process as they require less beneficiation due to the higher iron content. However, DSO ores can contain significantly higher concentrations of penalty elements, typically being higher in phosphorus, water content, and aluminium. Export-grade DSO ores are generally in the 62–64% Fe range.
Magmatic magnetite ore deposits
and ultrapotassic igneous rocks were sometimes used to segregate magnetite crystals and form masses of magnetite suitable for economic concentration. A few iron ore deposits, notably in Chile, are formed from volcanic flows containing significant accumulations of magnetite phenocrysts.Mine tailings
For every one ton of iron ore concentrate produced, approximately 2.5–3.0 tons of iron ore tailings will be discharged. Statistics show that there are 130 million tons of iron ore tailings discharged every year. If, for example, the mine tailings contain an average of approximately 11% iron, there would be approximately 1.41 million tons of iron wasted annually. These tailings are also high in other useful metals such as copper, nickel, and cobalt, and they can be used for road-building materials like pavement and filler and building materials such as cement, low-grade glass, and wall materials. While tailings are a relatively low-grade ore, they are also inexpensive to collect, as they do not have to be mined. Because of this, companies such as Magnetation have started reclamation projects where they use iron ore tailings as a source of metallic iron.The two main methods of recycling iron from iron ore tailings are magnetizing roasting and direct reduction. Magnetizing roasting uses temperatures between for a time of under 1 hour to produce an iron concentrate to be used for iron smelting. For magnetizing roasting, it is important to have a reducing atmosphere to prevent oxidization and the formation of Fe2O3 because it is harder to separate as it is less magnetic. Direct reduction uses hotter temperatures of over and longer times of 2–5 hours. Direct reduction is used to produce sponge iron to be used for steel-making. Direct reduction requires more energy, as the temperatures are higher and the time is longer, and it requires more reducing agent than magnetizing roasting.
Extraction
Lower-grade sources of iron ore generally require beneficiation, using techniques like crushing, milling, gravity or heavy media separation, screening, and silica froth flotation to improve the concentration of the ore and remove impurities. The results, high-quality fine ore powders, are known as fines.Magnetite
is magnetic, and hence easily separated from the gangue minerals and capable of producing a high-grade concentrate with very low levels of impurities.The grain size of the magnetite and its degree of commingling with the silica groundmass determine the grind size to which the rock must be comminuted to enable efficient magnetic separation to provide a high-purity magnetite concentrate. This determines the energy inputs required to run a milling operation.
Mining of banded iron formations involves coarse crushing and screening, followed by rough crushing and fine grinding to comminute the ore to the point where the crystallized magnetite and quartz are fine enough that the quartz is left behind when the resultant powder is passed under a magnetic separator.
Generally, most magnetite banded iron formation deposits must be ground to between to produce a low-silica magnetite concentrate. Magnetite concentrate grades are generally more than 70% iron by weight and usually are low in phosphorus, aluminium, titanium, and silica, and demand a premium price.
Hematite
Due to the high density of hematite relative to associated silicate gangue, hematite beneficiation usually involves a combination of beneficiation techniques. One method relies on passing the finely-crushed ore over a slurry containing magnetite or other agent such as ferrosilicon, which increases its density. When the density of the slurry is calibrated correctly, the hematite will sink and the silicate mineral fragments will float and can be removed.Production and consumption
| Country | Production |
| Australia | |
| Brazil | |
| China | |
| India | |
| Russia | |
| South Africa | |
| Ukraine | |
| United States | |
| Canada | |
| Iran | |
| Sweden | |
| Kazakhstan | |
| Other countries | |
| Total world |
Iron ore represents 93% of metals mined worldwide in 2021. Steel, of which iron is the key ingredient, represents almost 95% of all metal used per year.
Iron-rich rocks are common worldwide, but ore-grade commercial mining operations are dominated by the countries listed in the table aside. The major constraint to economics for iron ore deposits is not necessarily the grade or size of the deposits, because it is not particularly hard to geologically prove enough tonnage of the rocks exists. The primary constraint is the position of the iron ore relative to the market, the cost of rail infrastructure to get it to market, and the energy cost required to do so.
Mining iron ore is a high-volume, low-margin business, as the value of iron is significantly lower than that of base metals. It is highly capital-intensive and requires significant investment in infrastructure, such as rail, to transport the ore from the mine to a freight ship. For these reasons, iron ore production is concentrated in the hands of a few major players.
World production averages of raw ore annually. The world's largest producer of iron ore is the Brazilian mining corporation Vale, followed by Australian companies Rio Tinto and BHP. A further Australian supplier, Fortescue, has helped bring Australia's production to first in the world.
The seaborne trade in iron ore—that is, iron ore to be shipped to other countries—was in 2004. Australia and Brazil dominate the seaborne trade, with 72% of the market. BHP, Rio and Vale control 66% of this market between them.
In Australia, iron ore is won from three primary sources: pisolite "channel iron deposit" ore derived by mechanical erosion of primary banded-iron formations and accumulated in alluvial channels such as at Pannawonica; and the dominant metasomatically altered banded iron formation-related ores such as at Newman, the Chichester Range, the Hamersley Range and Koolyanobbing, Western Australia. Other types of ore are coming to the fore recently, such as oxidised ferruginous hardcaps, for instance laterite iron ore deposits near Lake Argyle in Western Australia.
The total recoverable reserves of iron ore in India are about of hematite and of magnetite. Chhattisgarh, Madhya Pradesh, Karnataka, Jharkhand, Odisha, Goa, Maharashtra, Andhra Pradesh, Kerala, Rajasthan, and Tamil Nadu are the principal Indian producers of iron ore. World consumption of iron ore grows 10% per year on average, with the main consumers being China, Japan, Korea, the United States, and the European Union.
China is currently the largest consumer of iron ore, which translates to being the world's largest steel-producing country. It is also the largest importer, buying 52% of the seaborne trade in iron ore in 2004. China is followed by Japan and Korea, which consume a significant amount of raw iron ore and metallurgical coal. In 2006, China produced of iron ore, with an annual growth of 38%.