Karjääri toodangumaht ja mõõtmed on suhteliselt suured.
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|  | Basic technological pelletizing operations are as follows:
Blasthole drilling in the open pit is executed by roller-bit drilling rigs. Blast holes are drilled with roller-drill bits 250mm in diameter. In greatly fissured or broken rocks for increasing steadiness the blasthole wellheads are cased with metal pipes 700mm in height. In area of Kostomuksha deposit all rocks need prior explosive preparation before ore excavation. At present time the following types of explosives are used:
 In connection with that the share of explosive operations comes to about 30% of production cost, the company looks for the ways of cost reduction for these operations. The share of explosive domestic manufacture runs 90% and it is not a limit. Continuous work on cost reduction goes on. At present time the company is coming to an end of release testing of low-granulotol "Aquatol T-8M", one of the most expensive components. Now the company is obtaining the authorization for test operation with explosive of type of "Aquaporit" in which granulotol content is zero.The blast holes are charged with:
Blast initiation is executed according to:
The overburden rocks prepared for excavation are loaded by front acting shovels on motor or rail transports and transported to outward bulldozer and steam shovel dumps, halleflinta is conveyed to the special stock house. According to mining-and-transportation segment of Project for the first stage of Kostomuksha mine reconstruction on the basis of new technology (approved in 1995), the system of quarrying with the following transportation operations is developed: external stacking for the overburden rocks and combined ore transportation through equalizing transfer sites.  The volume of lode rock (about 98%) is loaded by steam shovels on motor transport in pit-face and transported to intra-pit equalizing transfer sites and only small part of lode rock (2%) is loaded by steam shovels from pit-face directly on rail transport and transported to crushing-and-concentrating mill. In intra-pit equalizing transfer sites the lode rock is loaded by steam shovels on rail transport and transported to crushing-and-concentrating mill. The volume of friable deposits is loaded by steam shovels on motor transport, transported to external bulldozer dumps and stored along with the overburden rocks.During summer and fall the peat is loaded by walking excavator on motor transport for delivering to customers. According to mining-and-transportation segment of Project for the first stage of Kostomuksha mine reconstruction on the basis of new technology (approved in 1995), the system of quarrying with the following transportation operations is developed: external stacking for the overburden rocks and combined ore transportation through equalizing transfer sites. Ore crushing has three stages with:
 Concentration involves three stages of grinding, four operations of sizing, three stages of magnetic separation, three operations of desliming and one operation of fine screening. Basic manufacturing equipment includes:
 The refuse of magnetic separation and deslimer sinks go to sumps of sludge pump station and from where they are transferred to the tailing dump with use of soil pumps along sludge lines of 1200 mm across diameter.Tailing dump capacity is 460 million m3, square is 33.7 km2. Finished concentrate is directed to the thickening body where on the radial thickeners of 30m in diameter the concentrate is thickened to thickness of 50-60% of solid and moved to the workshop of pelletizing. Technological operations in pelletizing workshop covers concentrate filtering, damp pelletizing, and pellet roasting. Filtering Thickened concentrate comes in mixers and then is directed for filtering. Concentrate filtering is executed in vacuum filters. Mixing Filtering product (filter cake) is directed to the surge bin where then it is mixed with comminuted limestone and bentonite in proportions in accordance with the requirements of customers for their blast furnace process.
Roasting Finished pellets of +8mm in size are moved into traveling grate furnace where the pellets go through zones of drying and preheating, hard-heating (in large kiln) where they are heat-hardened at 1350 0C, recuperation, and cooling. High-temperature oxidizing roasting allows to reduce the content of sulfur in pellets and to run up to their high strength  Roasted pellets are graded to size of +5mm in fine screens. Fine pellets are directed to the pellet stockpile and then are delivered to customers for agglomeration.Finished products (fluxed and unfluxed pellets) are directed to the stock or to the loading hopper for forwarding them to the metallurgical plants. | ||||||||||||||||||||
Karelsky Okatysh
Karelsky Okatysh is the most modern iron ore mining complex in Russia. It produces a third part of iron ore pellets in Russia.
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ReservesReserves and resources 1.269 billion metric tonnes (2008, JORC)Sites
Indicative annual output
Indicative annual capacity
 Karelsky Okatysh produces
Who buys productsThe main consumer of Karelsky Okatysh products is Severstal Russian Steel (Cherepovets, Russia). Among other main consumers are Severstal International (Lucchini Piombino, Italy) and Corus (Netherlands).
Severstal is the second largest producer of iron ore pellets in Russia. Karelsky Okatysh produces about 30% of iron ore pellets in Russia. |
Iron ore
From Wikipedia, the free encyclopedia
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, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3). Hematite is also known as "natural ore". The name refers to the early years of mining, when certain hematite ores contained 66% iron and could 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.[1]
[edit]Sources
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. 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 utilisation of taconite in the United States, after World War II, and goethite orbog 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 bentonite 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, titanomagnetite, massive hematite andpisolitic ironstone deposits.
[edit]Banded iron deposits
Banded iron formations (BIF) are metamorphosed sedimentary rocks composed predominantly of thinly bedded iron minerals and silica (as quartz). The iron mineral present may be the carbonate siderite, but those used as iron ores contain the oxides magnetite or hematite.[2] Banded Iron formations are known as taconite within North America. Mining of BIF formations involves coarse crushing and screening, followed by rough crushing and fine grinding to comminute the ore to the point where the crystallised magnetite and quartz are fine enough that the quartz is left behind when the resultant powder is passed under a magnetic separator.
The mining involves moving tremendous amounts of ore and waste. The waste comes in two forms, bedrock in the mine (mullock) that isn't ore, 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.
The key economic parameters for magnetite ore being economic are the crystallinity of the magnetite, the grade of the iron within the BIF host rock, and the contaminant elements which exist within the magnetite concentrate. The size and strip ratio of most magnetite resources is irrelevant as BIF formations can be hundreds of metres thick, with hundreds of kilometres of strike, and can easily come to more than 2,500 million or more, tonnes of contained ore.
The typical grade of iron at which a magnetite-bearing banded iron formation becomes economic is roughly 25% Fe, which can generally yield a 33% to 40% recovery of magnetite by weight, to produce a concentrate grading in excess of 64% Fe by weight. The typical magnetite iron ore concentrate has less than 0.1% phosphorus, 3–7% silica and less than 3% aluminium.
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. Generally most magnetite BIF deposits must be ground to between 32 and 45 micrometres in order to provide a low-silica magnetite concentrate. Magnetite concentrate grades are generally in excess of 63% Fe by weight and usually are low phosphorus, low aluminium, low titanium and low silica and demand a premium price.
Currently magnetite iron ore is mined in Minnesota and Michigan in the U.S., and Eastern Canada mine taconite. Magnetite bearing BIF 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.
[edit]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% V2O5.[citation needed]
[edit]Hematite ore
Hematite iron ore deposits are currently exploited on all continents, with the largest intensity in South America, Australia and Asia. Most large hematite iron ore deposits are sourced from metasomatically altered banded iron formations and rarely igneous accumulations.
Hematite iron is typically rarer than magnetite bearing BIF or other rocks which form its main source or protolith rock, but it is considerably cheaper to process as it generally does not require beneficiation due to its higher iron content. However, Hematite ores are harder than magnetite ores and therefore require considerably more energy to crush and grind if benefication is required. Hematite ores can also 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 Hematite ores are generally in the 62–64% Fe range[citation needed].
[edit]Production and consumption
| Country | Production |
|---|---|
| China | 520 |
| Australia | 270 |
| Brazil | 250 |
| India | 150 |
| Russia | 105 |
| Ukraine | 73 |
| United States | 54 |
| South Africa | 40 |
| Iran | 35 [4] |
| Canada | 33 |
| Sweden | 24 |
| Venezuela | 20 |
| Kazakhstan | 15 |
| Mauritania | 11 |
| Other countries | 43 |
| Total world | 1690 |
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 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 exist. The main constraint is the position of the iron ore relative to market, the cost of rail infrastructure to get it to market and the energy cost required to do so.
World production averages one billion metric tons of raw ore annually. The world's largest producer of iron ore is the Brazilian mining corporation Vale, followed by Anglo-Australian companies BHP Billiton and Rio Tinto Group. A further Australian supplier, Fortescue Metals Group Ltd may eventually bring Australia's production to second in the world.
In Australia iron ore is won from three main sources: pisolite "channel iron deposit" ore derived by mechanical erosion of primary banded-iron formations and accumulated in alluvial channels such as at Pannawonica, Western Australia; 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 9,602 million tones of hematite and 3,408 million tones of magnetite. Madhya Pradesh, Karnataka, Bihar, Orissa, 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 annum[citation needed] 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 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. In 2006, China produced 588 million tons of iron ore, with an annual growth of 38%.
[edit]Depletion
Iron ore reserves at present seem quite vast, but some are starting to suggest that the maths of continual exponential increase in consumption can even make this resource seem quite finite. For instance, Lester Brown of theWorldwatch Institute has suggested iron ore could run out within 64 years based on an extremely conservative extrapolation of 2% growth per year.[5]
[edit]Smelting
Iron ores consists of oxygen and iron atoms bonded together into molecules. To convert it to metallic iron it must be smelted or sent through a direct reduction process to remove the oxygen. Oxygen-iron bonds are strong, and to remove the iron from the oxygen, a stronger elemental bond must be presented to attach to the oxygen. Carbon is used because the strength of a carbon-oxygen bond is greater than that of the iron-oxygen bond, at high temperatures. Thus, the iron ore must be powdered and mixed with coke, to be burnt in the smelting process.
However, it is not entirely as simple as that; carbon monoxide is the primary ingredient of chemically stripping oxygen from iron. Thus, the iron and carbon smelting must be kept at an oxygen deficient (reducing) state to promote burning of carbon to produce CO not CO2.
- Air blast and charcoal (coke): 2 C + O2
2 CO. - Carbon monoxide (CO) is the principal reduction agent.
- Stage One: 3 Fe2O3 + CO 2 Fe3O4 + CO2
- Stage Two: Fe3O4 + CO 3 FeO + CO2
- Stage Three: FeO + CO Fe + CO2
- Stage One: 3 Fe2O3 + CO
- Limestone fluxing chemistry: CaCO3 CaO + CO2
[edit]Trace elements
The inclusion of even small amounts of some elements can have profound effects on the behavioral characteristics of a batch of iron or the operation of a smelter. These effects can be both good and bad, some catastrophically bad. Some chemicals are deliberately added such as flux which makes a blast furnace more efficient. Others are added because they make the iron more fluid, harder, or give it some other desirable quality. The choice of ore, fuel, and flux determine how the slag behaves and the operational characteristics of the iron produced. Ideally iron ore contains only iron and oxygen. In reality this is rarely the case. Typically, iron ore contains a host of elements which are often unwanted in modern steel.
[edit]Silicon
Silica (SiO2) is almost always present in iron ore. Most of it is slagged off during the smelting process. At temperatures above 1300 °C some will be reduced and form an alloy with the iron. The hotter the furnace, the more silicon will be present in the iron. It is not uncommon to find up to 1.5% Si in European cast iron from the 16th to 18th centuries.
The major effect of silicon is to promote the formation of gray iron. Gray iron is less brittle and easier to finish than white iron. It is preferred for casting purposes for this reason. Turner (1900, pp. 192–197) reported that silicon also reduces shrinkage and the formation of blowholes, lowering the number of bad castings.
[edit]Phosphorus
Phosphorus (P) has four major effects on iron: increased hardness and strength, lower solidus temperature, increased fluidity, and cold shortness. Depending on the use intended for the iron, these effects are either good or bad. Bog ore often has a high Phosphorus content (Gordon 1996, p. 57).
The strength and hardness of iron increases with the concentration of phosphorus. 0.05% phosphorus in wrought iron makes it as hard as medium carbon steel. High phosphorus iron can also be hardened by cold hammering. The hardening effect is true for any concentration of phosphorus. The more phosphorus, the harder the iron becomes and the more it can be hardened by hammering. Modern steel makers can increase hardness by as much as 30%, without sacrificing shock resistance by maintaining phosphorus levels between 0.07 and 0.12%. It also increases the depth of hardening due to quenching, but at the same time also decreases the solubility of carbon in iron at high temperatures. This would decrease its usefulness in making blister steel (cementation), where the speed and amount of carbon absorption is the overriding consideration.
The addition of phosphorus has a down side. At concentrations higher than 0.2% iron becomes increasingly cold short, or brittle at low temperatures. Cold short is especially important for bar iron. Although, bar iron is usually worked hot, its uses often require it to be tough, bendable, and resistant to shock at room temperature. A nail that shattered when hit with a hammer or a carriage wheel that broke when it hit a rock would not sell well. High enough concentrations of phosphorus render any iron unusable (Rostoker & Bronson 1990, p. 22). The effects of cold shortness are magnified by temperature. Thus, a piece of iron that is perfectly serviceable in summer, might become extremely brittle in winter. There is some evidence that during the Middle Ages the very wealthy may have had a high phosphorus sword for summer and a low phosphorus sword for winter (Rostoker & Bronson 1990, p. 22).
Careful control of phosphorus can be of great benefit in casting operations. Phosphorus depresses the liquidus temperature, allowing the iron to remain molten for longer and increases fluidity. The addition of 1% can double the distance molten iron will flow (Rostoker & Bronson 1990, p. 22). The maximum effect, about 500 °C, is achieved at a concentration of 10.2% (Rostocker & Bronson 1990, p. 194). For foundry work Turner felt the ideal iron had 0.2–0.55% phosphorus. The resulting iron filled molds with fewer voids and also shrank less. In the 19th century some producers of decorative cast iron used iron with up to 5% phosphorus. The extreme fluidity allowed them to make very complex and delicate castings. But, they could not be weight bearing, as they had no strength (Turner 1900, pp. 202–204).
There are two remedies for high phosphorus iron. The oldest, and easiest, is avoidance. If the iron your ore produced was cold short, one would search for a new source of iron ore. The second method involves oxidizing the phosphorus during the fining process by adding iron oxide. This technique is usually associated with puddling in the 19th century, and may not have been understood earlier. For instance Isaac Zane, the owner of Marlboro Iron Works did not appear to know about it in 1772. Given Zane's reputation for keeping abreast of the latest developments, the technique was probably unknown to the ironmasters of Virginia and Pennsylvania.
Phosphorus is a deleterious contaminant because it makes steel brittle, even at concentrations of as little as 0.6%. Phosphorus cannot be easily removed by fluxing or smelting, and so iron ores must generally be low in phosphorus to begin with. The iron pillar of India which does not rust is protected by a phosphoric composition. Phosphoric acid is used as a rust converter because phosphoric iron is less susceptible to oxidation.
[edit]Aluminium
Small amounts of aluminium (Al) are present in many ores (often as clay) and some limestone. The former can be removed by washing the ore prior to smelting. Until the introduction of brick lined furnaces, the amount of aluminum contamination was small enough that it did not have an effect on either the iron or slag. However, when brick began to be used for hearths and the interior of blast furnaces, the amount of aluminium contamination increased dramatically. This was due to the erosion of the furnace lining by the liquid slag.
Aluminium is very hard to reduce. As a result aluminium contamination of the iron is not a problem. However, it does increase the viscosity of the slag (Kato & Minowa 1969, p. 37 and Rosenqvist 1983, p. 311). This will have a number of adverse effects on furnace operation. The thicker slag will slow the descent of the charge, prolonging the process. High aluminium will also make it more difficult to tap off the liquid slag. At the extreme this could lead to a frozen furnace.
There are a number of solutions to a high aluminium slag. The first is avoidance; don't use ore or a lime source with a high aluminium content. Increasing the ratio of lime flux will decrease the viscosity (Rosenqvist 1983, p. 311).
[edit]Sulfur
Sulfur (S) is a frequent contaminant in coal. It is also present in small quantities in many ores, but can be removed by calcining. Sulfur dissolves readily in both liquid and solid iron at the temperatures present in iron smelting. The effects of even small amounts of sulfur are immediate and serious. They were one of the first worked out by iron makers. Sulfur causes iron to be red or hot short (Gordon 1996, p. 7).
Hot short iron is brittle when hot. This was a serious problem as most iron used during the 17th and 18th century was bar or wrought iron. Wrought iron is shaped by repeated blows with a hammer while hot. A piece of hot short iron will crack if worked with a hammer. When a piece of hot iron or steel cracks the exposed surface immediately oxidizes. This layer of oxide prevents the mending of the crack by welding. Large cracks cause the iron or steel to break up. Smaller cracks can cause the object to fail during use. The degree of hot shortness is in direct proportion to the amount of sulfur present. Today iron with over 0.03% sulfur is avoided.
Hot short iron can be worked, but it has to be worked at low temperatures. Working at lower temperatures requires more physical effort from the smith or forgeman. The metal must be struck more often and harder to achieve the same result. A mildly sulfur contaminated bar can be worked, but it requires a great deal more time and effort.
In cast iron sulfur promotes the formation of white iron. As little as 0.5% can counteract the effects of slow cooling and a high silicon content (Rostoker & Bronson 1990, p. 21). White cast iron is more brittle, but also harder. It is generally avoided, because it is difficult to work, except in China where high sulfur cast iron, some as high as 0.57%, made with coal and coke, was used to make bells and chimes (Rostoker, Bronson & Dvorak 1984, p. 760). According to Turner (1900, pp. 200), good foundry iron should have less than 0.15% sulfur. In the rest of the world a high sulfur cast iron can be used for making castings, but will make poor wrought iron.
There are a number of remedies for sulfur contamination. The first, and the one most used in historic and prehistoric operations, is avoidance. Coal was not used in Europe (unlike China) as a fuel for smelting because it contains sulfur and therefore causes hot short iron. If an ore resulted in hot short metal, ironmasters looked for another ore. When mineral coal was first used in European blast furnaces in 1709 (or perhaps earlier), it was coked. Only with the introduction of hot blast from 1829 was raw coal used.
Sulfur can be removed from ores by roasting and washing. Roasting oxidizes sulfur to form sulfur dioxide which either escapes into the atmosphere or can be washed out. In warm climates it is possible to leave pyritic ore out in the rain. The combined action of rain, bacteria, and heat oxidize the sulfides to sulfates, which are water soluble (Turner 1900, pp. 77). However, historically (at least), iron sulfide (iron pyrite FeS2), though a common iron mineral, has not been used as an ore for the production of iron metal. Natural weathering was also used in Sweden. The same process, at geological speed, results in the gossan limonite ores.
The importance attached to low sulfur iron is demonstrated by the consistently higher prices paid for the iron of Sweden, Russia, and Spain from the 16th to 18th centuries. Today sulfur is no longer a problem. The modern remedy is the addition ofmanganese. But, the operator must know how much sulfur is in the iron because at least five times as much manganese must be added to neutralize it. Some historic irons display manganese levels, but most are well below the level needed to neutralize sulfur (Rostoker & Bronson 1990, p. 21).
[edit]References
 | This article includes a list of references or external links, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations where appropriate. (April 2009) |
- ^ "IRON ORE - Hematite, Magnetite & Taconite". Mineral Information Institute. Retrieved 7 April 2006.
- ^ Harry Klemic, Harold L. James, and G. Donald Eberlein, (1973) "Iron," in United States Mineral Resources, US Geological Survey, Professional Paper 820, p.298-299.
- ^ "U.S. Geological Survey". Retrieved 2008-01-29.
- ^ http://www.bgs.ac.uk/mineralsuk/commodity/world/home.html
- ^ Brown, Lester Plan B 2.0, New York: W.W. Norton, 2006. p. 109
- Gordon, Robert B. (1996), American Iron 1607-1900, The Johns Hopkins University Press
- Rostoker, William; Bronson, Bennet (1990), Pre-Industrial Iron: Its Technology and Ethnology, Archeomaterials Monograph No. 1
- Turner, Thomas (1900), The Metallurgy of Iron (2nd ed.), Charles Griffin & Company, Limited
- Kato, Makoto and Susumu Minowa (1969), "Viscosity Measurement of Molten Slag- Properties of Slag at Elevated Temperature (Part 1)", Transactions of the Iron and Steel Institute of Japan (Tokyo: Nihon Tekko Kyokai) 9: 31–38
- Rosenqvist, Terkel (1983), Principles of Extractive Metallurgy, McGraw-Hill Book Company
- Rostoker, William; Bronson, Bennet; Dvorak, James (1984), "The Cast-Iron Bells of China", Technology and Culture (The Society for the History of Technology) 25 (4): 750–767
[edit]External links
Rauamaak
Allikas: Vikipeedia
Rauamaak on kivim või mineraal, mis sisaldab piisavalt rauda ning on piisavalt hõlpsalt ligipääsetav, et tema kaevandamine oleks majanduslikult tasuv.
Raud esineb enamasti oksiidsete mineraalide koosseisus, näiteks hematiit (Fe2O3), magnetiit (Fe3O4) või götiit (Fe3+O(OH)). Peale oksiidide võivad rauamaagiks olla ka näiteks püriit (FeS) ja sideriit (FeCO3).
Vahest nimetatakse rauamaagiks ka rauda sisaldavat kivimkeha, mille kaevandamine ei ole majanduslikult tasuv. Näiteks leidub Eesti maapõues ligi 500 miljonit tonni magnetiiti, mis suure lasumussügavuse tõttu esialgu kasutamist ei leia, mida aga siiski mõnikord rauamaagiks nimetatakse.
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