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 (Fe 3O 4, 72.4% Fe), hematite (Fe2O 3, 69.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH)·n(H2O), 55% Fe) or siderite (FeCO3, 48.2% Fe).Deepslate iron ore is a variant of iron ore that can generate in deepslate and tuff blobs.
Ores containing very high quantities of hematite or magnetite (greater than about 60% iron) are known as “natural ore” or “direct shipping ore”, meaning they 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 main raw materials to make steel—98% of the mined iron ore is used to make steel. iron ore is “more integral to the global economy than any other commodity, except perhaps oil”.
Metallic iron is virtually unknown on the surface of the Earth except as iron-nickel alloys from meteorites and very rare forms of deep mantle xenoliths. Some iron meteorites are thought to have originated from accreted bodies 1,000 km in diameter or larger. The origin of iron can be ultimately traced to formation through nuclear fusion in stars and most of the iron is thought to have originated in dying stars that are large enough to collapse or explode as supernovae. Although iron is the fourth-most abundant element in the Earth’s crust, composing about 5%, the vast majority is bound in silicate or more rarely carbonate minerals (for more information, see iron cycle). The thermodynamic barriers to separating pure iron from these minerals are formidable and energy-intensive, therefore all sources of iron used by human industry exploit comparatively rarer iron oxide minerals, primarily hematite.
Prior to the industrial revolution, most iron was obtained from widely available goethite or bog ore, for example during the American Revolution and the Napoleonic Wars. Prehistoric societies used laterite as a source of iron ore. Historically, much of the iron ore utilized by industrialized societies has been mined from predominantly hematite deposits with grades of around 70% Fe. These deposits are commonly referred to as “direct shipping ores” or “natural ores”. Increasing iron ore demand, coupled with the depletion of high-grade hematite ores in the United States, after World War II led to development of lower-grade iron ore sources, principally the utilization of magnetite and taconite.
Banded iron formations
2.1-billion-year-old rock showing banded iron formation.
Processed taconite pellets with reddish surface oxidation as used in the steelmaking industry, with a U.S. quarter (diameter: 24 mm [0.94 in]) shown for scale.
Banded iron formations (BIFs) are sedimentary rocks containing more than 15% iron composed predominantly of thinly bedded iron minerals and silica (as quartz). Banded iron formations occur exclusively in Precambrian rocks, and are commonly weakly to intensely metamorphosed. Banded iron formations may contain iron in carbonates (siderite or ankerite) or silicates (minnesotaite, greenalite, or grunerite), but in those mined as iron ores, oxides (magnetite or hematite) 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 (overburden or interburden locally known as mullock), and unwanted minerals which are an intrinsic part of the ore rock itself (gangue). 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.
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, titanomagnetite, massive hematite and pisolitic ironstone deposits.
The key economic 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 is 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 in excess of 64% iron by weight. The typical magnetite iron ore concentrate has less than 0.1% phosphorus, 3–7% silica and less than 3% aluminium.
Currently magnetite iron ore is mined in Minnesota and Michigan in the U.S., Eastern Canada and Northern Sweden. Magnetite-bearing banded iron formation is currently mined extensively in Brazil, 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 (DSO) deposits (typically composed of hematite) 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 rarely igneous accumulations.
DSO deposits are typically rarer than the magnetite-bearing BIF or other rocks which form its main 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 (especially pisolite sedimentary accumulations) and aluminium (clays within pisolites). Export-grade DSO ores are generally in the 62–64% Fe range.
Magmatic magnetite ore deposits
Occasionally granite and ultrapotassic igneous rocks 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. Chilean magnetite iron ore deposits within the Atacama Desert have also formed alluvial accumulations of magnetite in streams leading from these volcanic formations.
Some magnetite skarn and hydrothermal deposits have been worked in the past as high-grade iron ore deposits requiring little beneficiation. There are several granite-associated deposits of this nature in Malaysia and Indonesia.
Other sources of magnetite iron ore include metamorphic accumulations of massive magnetite ore such as at Savage River, Tasmania, formed by shearing of ophiolite ultramafics.
Another, minor, source of iron ores are magmatic accumulations in layered intrusions which contain a typically titanium-bearing magnetite often with vanadium. These ores form a niche market, with specialty smelters used to recover the iron, titanium and vanadium. These ores are beneficiated essentially similar to banded iron formation ores, but usually are more easily upgraded via crushing and screening. The typical titanomagnetite concentrate grades 57% Fe, 12% Ti and 0.5% V
For every 1 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 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 don’t have to be mined. Because of this companies such as Magnetation, Inc., 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 700 and 900 °C for a time of under 1 hour to produce an iron concentrate (Fe3O4) 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 1000 °C and longer times of 2–5 hours. Direct reduction is used to produce sponge iron (Fe) 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.
Iron ore distribution in China is mainly concentrated in Liaoning, Sichuan, Hebei, Beijing, Shanxi, Inner Mongolia, Shandong, Henan, Hubei, Yunnan, Anhui, Fujian, Jiangxi, Hainan, Guizhou, Shaanxi, Gansu, Qinghai and Xinjiang.
Large iron ore distribution area abroad
National mine name reserves / 100 million tons of Fe% of reserves in the country
Hamesley, Australia 3205791
Brazilian iron corner 3003565
Caracas, Brazil 1806035
Traffic inconvenience not developed in wurukum (Brazil) of Matong (glass) of Bolivia and Brazil 58050.53
Orissa 676029, Bihar, India
Labrador, Canada 206 3851
Sulpiril 1633194, USA
Kursk 4354638, Russia
Russian kaczkarner 14012
Ukraine, rivorog 1943617
Lorraine 773395, France
Kiruna, Sweden 345866
Bolivar, Venezuela 24599
Ningba mining area, Liberia and Guinea 2060
Distribution of stone source
There are two characteristics of iron ore resources in China: first, there are many poor ores, and the reserves of poor resources account for 80% of the total; Second, there are many complex ores with multi element symbiosis. In addition, the ore body is complex; Some iron poor deposits are hematite at the upper part and magnetite at the lower part.
The iron ore deposits in Northeast China are mainly Anshan mining area, which is the largest mining area in China. Large ore bodies are mainly distributed in Anshan (including DAARC mountain, yingtaoyuan, east-west Anshan, etc.), Benxi (Nanfen, Waitoushan, tongyuanbao, etc.), Liaoyang (Gongchangling), and some of the deposits are distributed near Tonghua in Jilin Province. Anshan mining area is the main raw material base of Angang and Bengang.
The main characteristics of Anshan mining area are: except for few rich ores, 98% of the reserves are poor, with 20-40% iron content and an average of 30%. It must be processed by beneficiation, and the iron content can reach more than 60% after the selection.
2) The ore minerals are magnetite and hematite, and some are pseudo hematite and semi pseudo hematite. The structure is compact and hard, gangue is distributed evenly and compact, and it is difficult to beneficiation and the ore reduction is poor.
3) Most gangue minerals are composed of quartz, SiO2 is 40-50%. But tongyuanbao iron mine is a self-soluble ore with a alkalinity of more than 1. The results show that 1.29-7.5% of manganese can be used instead of manganese ore.
4) The ore contains few impurities of S and P, and Benxi Nanfen Iron Mine has a low P content, which is a good raw material for smelting high quality pig iron.
It is mainly distributed in the Wuan and Fengfeng mining areas in Xuanhua, Qian’an and Handan areas of Hebei Province. Mining villages and other areas, as well as Inner Mongolia and Shanxi. It is the raw material base of Shougang, Baogang, Taigang and Handan, Xuanhua and Yangquan steel plants.
Qianluan mine is Anshan type magnetite, which contains acid gangue, less s and P impurities, and has good ore selectivity.
The ore in Hanxing mining area is mainly hematite and magnetite, the iron content of ore is between 40% and 55%, and the gangue contains some alkaline oxides, and some ores are high s.
Central South Region
The iron ore in central and southern China is mainly Daye iron ore in Hubei Province. Other places, such as Xiangtan in Hunan, Anyang and Wuyang in Henan Province, Hainan Island in Jiangxi and Guangdong Province, have considerable reserves. These mining areas are the raw material supply bases of WISCO, Xianggang and various large and medium blast furnaces in the region.
Daye mining area is one of the earliest mining areas in China, mainly including Tieshan, Jinshandian, Chengchao, Lingxiang and other mines, with abundant reserves. The ore is mainly iron copper co-occurrence ore, iron ore is magnetite, followed by hematite, and other chalcopyrite and pyrite. The iron content of ore is 40-50%, and the highest is 54-60%. Gangue minerals include calcite, quartz, etc., and the gangue contains about 28% SiO2, with a certain solvability (cao/sio2 is about 0.3), and the ore contains low P (generally 0.027%), high s content and great fluctuation (0.01-1.2%), and contains Cu (0.2-1.0%) and CO (0.013-0.025%) and other non-ferrous metals. The ore has poor reducibility, and the ore is sintered and pelletized and then smelted in blast furnace.
The iron ore producing areas in East China are mainly from Wuhu in Anhui Province to concave mountain in Nanjing, Jiangsu Province, Nanshan, Gushan, Taochong, Meishan, Fenghuang Mountain and other mines. In addition, Jinling town in Shandong Province also has abundant iron ore resources storage, which is the raw material supply base of Ma’anshan Iron and steel company and other iron and steel enterprises.
The iron ore in Wuning mining area is mainly hematite, followed by magnetite, and some sulfide ores such as chalcopyrite and pyrite. The iron ore has a high grade, and some rich ores (including fe50% – 60%) can be smelted directly in the furnace. Some of the poor ores should be selected by beneficiation and sintered to make blocks for blast furnace. The ore has better reducibility. Gangue minerals are quartz, calcite, apatite and rutile, etc. the ore contains high s and P impurities (P is generally 0.5%, the highest is 1.6%, and the average s content of Meishan Iron Mine can reach 2% – 3%), the ore has a certain solvability (for example, the average alkalinity of the rich ores in Youshan and Meishan can reach 0.7-0.9), and some ores contain non-ferrous metals such as V, Ti and Cu.
In addition to the above areas, there are abundant iron ore resources in Southwest China and Northwest China, such as Sichuan, Yunnan, Guizhou, Gansu, Xinjiang and other places.