Nature, properties and uses
Iron is the commonest, cheapest and most versatile of all metals. It is, in fact, the basis of the modern industrial complex, About 90 percent of the world’s iron ore is used in the making of steel. A host of secondary industries are based on iron and steel, including construction of automobiles, aircrafts, bridges, machines and other equipment. Its magnetic properties make it indispensable in electrical engineering, where it constitutes an essential part of the dynamo, the motor, telephone, telegraph, radio and other electrical appliances. It has a high ductility and can be drawn into bars or wires of varying sizes without snapping. Besides its great strength and toughness, it is also elastic and can withstand great stresses without any appreciable distortion. When alloyed with other metals, such as nickel and chromium, it has increased resistance to heat, shock and abrasion. These are useful properties in making tools, machine parts, springs and stainless steel.
Types of iron ores
Generally speaking, the world’s principal source of iron ores belong to one of the following kinds.
- Magnetite: It has the richest metallic iron content (55-72 percent) with high magnetic qualities, excellent for the electrical industry. It is mainly from igneous rocks and is black in colour. The Swedish iron fields at Kiruna have some of the world’s best magnetite iron ores, so also are the Bomi Hills and those on Mt. Nimba in the Bong Hills of Liberia, which are 65 percent iron.
- Haematite: Is another high-grade iron ore with a metallic content of 50 to 70 percent. It is mainly from sedimentary sources and is reddish in appearance. Most of the iron from the Lake Superior region is haematite. Haematite ores are also found in the metamorphosed Birrimian sediments around Marampa and Lunsar and in the Sula Mountains in Sierra Leone. They are also found near Fort Gouraud, Mauritania where the content is 64 percent iron.
- Limonite: This is common most of the commercially workable iron ores. Its metallic content is up to 60 percent but it is heavily charged with impurities. It is brown in colour and is formed by the decomposition of other iron-bearing minerals. It is sometimes called ‘bog iron ore’ as it occurs in lakes and swamps. Examples in West Africa include the deposits near Conakry, Guinea and those of Mt. Patti, Lokoja in Nigeria.
- Siderite: It is one of the low-grade iron ores with a metallic content of not more than 45 percent.Itis a residual ore deposited as a sediment when other rock materials have been eroded and carried away. There are important deposits of siderite ore in the Cleveland Hills and around Scunthorpe in England and in Lorraine, France, where the ore contains a high proportion of phosphorus.
Iron and steel processing
In the olden days, crude iron was made simply by heating iron ore in a charcoal fire. When the fire died down, lumps of compact iron were left behind and could be hammered into various shapes to make tools and weapons. Later on, bellows were used to speed up the heating process. By the fourteenth century, furnaces were used to smelt the iron on a large scale. This produced pig iron which could be used for making steel. The liquid iron could also be poured into moulds to make cast iron for shaping into pipes, bars and plates. The finished products were hard and tough but brittle. With the coming of the Industrial Revolution, when the demand for iron and steel products reached a new peak, modern blast furnaces were introduced. These smelt the iron at a very high temperature of 593°C (1100° F.). Apart from iron ore, raw materials such as coke and limestone are required. Water and air are used in prodigious quantities, and other metals are added to produce all kinds of alloyed steel, each with its own specific qualities.
With the march of time, improved methods such as the open-hearth process, the Gilchrist Thomas process (specially developed to smelt iron with very high phosphorus content) and the electric furnace have been developed.
Changing location in the world’s iron and steel industry: A comparison of the present distribution of the iron and steel industry and that of the last century or some centuries ago will reveal that many changes have taken place. In the early days of iron production, small scattered works were concentrated in areas where iron ore was found and where timber was available from the forests to provide charcoal for smelting the ore.
Nearness to water supply was an advantage as it helped to cool the bellows that were used to supply the ‘blast’ that smelted the iron. Such primitive methods of iron smelting could only produce a, few tonnes of iron to meet local demand and the industry was scattered in many places, especially in Europe, wherever ore deposits occurred near large forests.
By the end of the eighteenth century, when coal was found to be a much more efficient form of fuel than charcoal, blast furnaces began to be built on the major coalfields. Besides, many coalfields also produced coke, which is essential for fusing with the iron to make steel. Moreover, the traditional techniques in those days needed eight to ten times as much coal as iron to smelt a given quantity of steel. It was thus far more economical to bring iron ore to existing coalfields than to transport coal to the iron ore fields. Large-scale iron and steel works thus began to be concentrated around the world’s coalfields, and many of them owed their growth to industrial inertia, the inherited reservoir of skilled labour, technology, transport network and industrial establishments. They still persist today as industrial regions e.g. Midlands of England, Central Valley of Scotland, South Wales, the Ruhr region of Germany, the Franco-Belgian Coalfield area, the Appalachian-Pittsburg region of U.S.A. and the Donetz region of Ukraine.
By the late nineteenth century, improvement in the technology of iron and steel making made it possible for an equal amount of coal and coke (or even less) to smelt a given quantity of iron. The coalfields began to lose their pull on the siting of the iron and steel industry. Other more favourable locations were developed to house the modern blast furnaces. Many coastal locations were preferred for obvious reasons: ease of assembly of the raw materials for iron and steel making (coal, coke, iron ores, ferro-alloys, even oil) ease of disposal of the finished products and often nearness to the consumer market. Some steel works in older inland coalfields e.g. in South Wales, have been closed down in the face of the newer plants with coastal location like Margam and Newport. Similarly, many new steel plants have been established along the eastern coast of U.S.A. (e.g. Sparrows Points) or along the St. Lawrence-Great Lakes region (e.g. Chicago and Hamilton) at the expense of the more interior steel towns like Pittsburgh, and iron ore is imported from as far as the orefields at Schefferville, Labrador.
Malaysia’s iron and steel works is coastally located at Prai, importing coal and drawing iron from inland fields.
The location of the world’s iron and steel industry is still in a state of transition in the face of rapidly changing techniques of iron smelting and refining, which will have world-wide repercussions on the rise or decline of world industrial areas.
World production and distribution of iron and steel
Three countries, Russia, USA and Japan are the leading producers in both iron ore and steel. The USA used to be the leading producer in steel while the Russia led in iron ore. But, the Russia has overtaken the USA in steel production and increased its lead in iron ore production. The Russia now accounts for 29 percent of world iron ore production and 24 percent of the crude steel. Its greatest single iron field is at Krivoi Rog to the north of the Black Sea. Much smelting and steel production is done in the Donetz Basin. Iron ore is mined in the Kerch Peninsula, with steel works on the shores of the Sea of Azov. Other iron and steel producing areas are Magnitogorsk (magnetite iron) Nizhny Tagil and Ivdel of the Urals; and the Kuznetz basin in Siberia.
The USA used to account for 15 percent of world iron ore production and 12 percent of the crude steel (1967). But now it accounts for only 5 percent of world iron ore production and 12 percent of the crude steel. The iron ore deposits in the Mesabi Hills, south-west of Lake Superior, were once all important, but they are now almost exhausted. The major steel areas are in Pittsburgh, and the Great Lakes region stretching from Chicago to Detroit and Buffalo; the Eastern Atlantic States centred on Philadelphia and Baltimore; the south-east, centred on Birmingham, Alabama; and the west, in Fontana (Los Angeles) and San Francisco. Much ore is now imported from fields in Labrador, Canada and from Brazil, Venezuela, Liberia and Guinea Republic. Hence, the USA is able to account for 9 percent of world pig iron production.
Japan does not produce much iron ore but imports from other countries. It now accounts for 16 percent of world pig iron production and 15 percent of the crude steel. Japan’s own iron ore, mined at Kemaishi and Kutchen hardly supplies 10 percent of her industrial needs. Much scrap iron is used to supplement her deficiency in iron ore. The main sources of iron ore import to Japan are the Philippines and Australia.
China, like Japan, has also increased in importance as a world producer of iron and steel. It now accounts for 12 per cent (formerly 5%) of world iron ore; 8 per cent of pig iron and 6 per cent (formerly 2%) of crude steel production. China’s iron ore deposits are located at Aushan, Manchuria; Tayeh, Hupie, where Wuham (Wuchang, Hanyang and Hankow) is the leading iron and steel district. New areas are also increasing production e.g. Paotow in Inner Mongolia, Taiyuan in Shansi and Chungking in Szechwan.
India produces 5 percent of the world’s iron ore (mainly haematite) from her outcrops in Bihar and Orissa. These areas also contain India’s largescale iron and steel works at Jamshedpur, Dugapur, Rourkela and Bhilai. India accounts for 2 percent of world pig iron and nearly 2 percent of the crude steel.
Brazil produces nearly 17 percent of world iron ore but it accounts for only 2 percent of the pig iron and only 1 percent of the crude steel.
This means that Brazil exports most of its iron ore. However, it has steel works at Volta Redonda and Horizonte. Brazil’s iron ore comes mainly from the large iron ore deposits in Itabira, in the mineral-rich Minas Gerais district. The other iron and steel areas are mostly in Europe, including Germany, France, United Kingdom, Sweden, Italy, Belgium, Poland and Czech and Slovak Republics.
In Europe, there is far more coal than iron. The French iron and steel industry in the north-eastern industrial district depends on local Lorraine iron ore and coal from the Franco-Belgian coalfield. Some ore is available from Sweden and Mauritania and is used in the steelworks in Dunkirk.
The greatest iron and steel centre of Germany is in the Ruhr region, where the imported iron ore from Luxembourg and Sweden is smelted with excellent coking coals from the Ruhr Coalfields. In Scandinavia are high-quality haematite and magnetite iron ore deposits at Kiruna and Gallivare, Lapland and in the Swedish Lake Depression. Much of the iron is used locally at Stockholm and Eskilstuna, with imported coke from Germany and Britain for making steel. Of the major steel producers, Britain has least iron, mainly low-grade siderite ores of the Jurassic rocks from the Cleveland Hills, Lincolnshire and Northamptonshire. Much has to be imported from Sweden, Spain (from the Cantabrian Mountains) and France, to be smelted with local coking coal. There are iron and steel works in Northamptonshire, South Wales, Middlesborough and the Central Valley of Scotland.
The southern continents have rich deposits of iron ore but make little steel. Australia’s iron ore is at Mt. Tom Price, Iton Knob, Yampi Sound and there are steel works at Whyalla, Newcastle and Port Kembla. Australia is self-sufficient in iron and steel. There are also rich ore deposits in the south of Venezuela. Africa is rich in iron ore but has little coal. High-grade deposits are being exploited in Liberia and Mauritana. Vereeniging in South Africa is the centre of the iron and steel industry.
Environmental effects of mining
As useful as mining is to the economy of a country, it is also harmful to the environment in many ways. Mining involves the digging up of land thereby rendering many hectares of land derelict. In this regard, the small-scale type of mining known as quarrying is the most damaging to the environment because it is more widespread than large-scale mining which is localized in certain areas.
The hollows and ditches created in mining areas may be filled by runoff from rainfall to become stagnant pools of water. In some parts of the world e.g. Britain, such pools have been carefully managed and kept clean for use for recreational purposes (fishing, boating). But in most areas, the pools have become breeding grounds for insect pests, such as the mosquitoes which cause malaria. In other cases, the ditches are used as a dumping ground for solid wastes. Such waste dumps damage the aesthetic value of the land and may become breeding grounds for flies and germs which are harmful to man. Cholera and dysentery are two common epidemic diseases which may arise from food contamination by such flies and germs.
The clearing away of the vegetation, the exposure and the digging up of the land in mining areas often leads to accelerated soil erosion. Thus, mining areas are notorious for gully erosion, a typical example being the Jos Plateau tin mining areas. Huge volumes of sediments are generated in mining areas. The dumphills destroy the beauty of the landscape and then the sediments may be carried by runoff water into streams and lakes. The sediments silt-up and pollute these water bodies. Such polluted rivers and streams may lose their fish. Furthermore, water from them is not safe for drinking.
Pollution of water bodies and the landscape in general is very common in petroleum mining areas.
The pollution occurs through (a) blow-out or explosion of oil wells; (b)leakage or bursting of oil pipelines; (c) leakage of oil at oil terminals (ports); (d) leakage of oil from oil tankers at sea and (e) marine accidents involving the collision of an oil tanker with another ship. Oil pollution is a major environmental hazard in the Delta areas of Nigeria. The oil pollution has rendered many farmlands and fishing grounds unproductive. The white sandy beaches along the shore also have been contaminated, making them unsuitable for recreation.
Air pollution is another major hazard in mining areas. The most common cause of air pollution is the dust from the mines. The dust particles not only pollute the air, they cover up the plant leaves, thereby inhibiting the process of photosynthesis, respiration and transpiration. Other sources of pollution include smoke, soot and poisonous gases especially in coal mining areas. The breathing in of such dusts by man may ultimately lead to lung diseases.