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86-697: 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 3 O 4 , 72.4% Fe), hematite ( Fe 2 O 3 , 69.9% Fe), goethite ( FeO(OH) , 62.9% Fe), limonite ( FeO(OH)·n(H 2 O) , 55% Fe), or siderite ( FeCO 3 , 48.2% Fe). Ores containing very high quantities of hematite or magnetite, typically greater than about 60% iron, are known as natural ore or direct shipping ore , and can be fed directly into iron-making blast furnaces . Iron ore

172-420: A laboratory or factory . Mining in a wider sense comprises extraction of any resource (e.g. petroleum , natural gas , salt or even water ) from the earth. Mining of rock and metals has been done since prehistoric times. Modern mining processes involve prospecting for mineral deposits, analysis of the profit potential of a proposed mine, extraction of the desired materials, and finally reclamation of

258-515: 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 . 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

344-497: 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 determines 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. Rock (geology) In geology , rock (or stone )

430-402: A fourth class of rocks alongside igneous, sedimentary, and metamorphic. Rock varies greatly in strength, from quartzites having a tensile strength in excess of 300 MPa to sedimentary rock so soft it can be crumbled with bare fingers (that is, it is friable ). (For comparison, structural steel has a tensile strength of around 350 MPa. ) Relatively soft, easily worked sedimentary rock

516-433: A huge impact on the cultural and technological development of the human race. Rock has been used by humans and other hominids for at least 2.5 million years . Lithic technology marks some of the oldest and continuously used technologies. The mining of rock for its metal content has been one of the most important factors of human advancement, and has progressed at different rates in different places, in part because of

602-424: A premium price. 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 properly calibrated, the hematite will sink and

688-452: 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 700 and 900 °C (1,292 and 1,652 °F) for

774-562: A source area and then transported to the place of deposition by water , wind , ice , mass movement or glaciers (agents of denudation ). About 7.9% of the crust by volume is composed of sedimentary rocks, with 82% of those being shales, while the remainder consists of 6% limestone and 12% sandstone and arkoses . Sedimentary rocks often contain fossils . Sedimentary rocks form under the influence of gravity and typically are deposited in horizontal or near horizontal layers or strata , and may be referred to as stratified rocks. Sediment and

860-600: A source of iron ore. 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 . 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

946-594: A switch to index-based quarterly pricing by the world's three largest iron ore miners— Vale , Rio Tinto , and BHP —in early 2010, breaking a 40-year tradition of benchmark annual pricing. Iron is the most abundant element on earth but not in the crust. The extent of the accessible iron ore reserves is not known, though Lester Brown of the Worldwatch Institute suggested in 2006 that iron ore could run out within 64 years (that is, by 2070), based on 2% growth in demand per year. Geoscience Australia calculates that

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1032-713: A texture are referred to as foliated ; the remainders are termed non-foliated. The name of the rock is then determined based on the types of minerals present. Schists are foliated rocks that are primarily composed of lamellar minerals such as micas . A gneiss has visible bands of differing lightness , with a common example being the granite gneiss. Other varieties of foliated rock include slates , phyllites , and mylonite . Familiar examples of non-foliated metamorphic rocks include marble , soapstone , and serpentine . This branch contains quartzite —a metamorphosed form of sandstone —and hornfels . Though most understanding of rocks comes from those of Earth, rocks make up many of

1118-588: A three-chambered concentric roasting furnace, before passing the ore to a separate reducing furnace for smelting. Details of this mill were the invention of Charles Sanderson, a steel maker of Sheffield, who held the patent for it. These differences between spathic ore and haematite have led to the failure of a number of mining concerns, notably the Brendon Hills Iron Ore Company . Spathic iron ores are rich in manganese and have negligible phosphorus. This led to their one major benefit, connected with

1204-416: A time of under 1 hour to produce an iron concentrate (Fe 3 O 4 ) to be used for iron smelting. For magnetizing roasting, it is important to have a reducing atmosphere to prevent oxidization and the formation of Fe 2 O 3 because it is harder to separate as it is less magnetic. Direct reduction uses hotter temperatures of over 1,000 °C (1,830 °F) and longer times of 2–5 hours. Direct reduction

1290-461: A typical European high-phosphorus ore in Bessemer's converter gave a poor quality steel. To produce high quality steel from a high-phosphorus ore, Mushet realised that he could operate the Bessemer converter for longer, burning off all the steel's impurities including the unwanted phosphorus but also the carbon (which is an essential ingredient in steel), and then re-adding carbon, along with manganese, in

1376-654: 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 similarly 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 2 O 5 . 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,

1462-628: A value of $ 2.3 billion. 46% of Canada's iron ore comes from the Iron Ore Company of Canada mine, in Labrador City , Newfoundland , with secondary sources including the Mary River Mine in Nunavut . According to the U.S. Geological Survey's 2021 Report on iron ore, India is estimated to produce 59,000,000 t (58,000,000 long tons; 65,000,000 short tons) of iron ore in 2020, placing it as

1548-507: Is a high-volume, low-margin business, as the value of iron is significantly lower than base metals. It is highly capital intensive, and requires significant investment in infrastructure such as rail in order 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 2,000,000,000 t (2.0 × 10 long tons; 2.2 × 10 short tons) of raw ore annually. The world's largest producer of iron ore

1634-604: Is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition , and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust , and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere . The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy . It may be limited to rocks found on Earth, or it may include planetary geology that studies

1720-426: Is expected to rise by a CAGR of 2% between 2023 and 2027, and industry analyst Fitch Solutions forecasted in 2021 that Brazil's annual production will reach 592,000,000 t (583,000,000 long tons; 653,000,000 short tons) by 2030. In 2017, Canadian iron ore mines produced 49,000,000 t (48,000,000 long tons; 54,000,000 short tons) of iron ore in concentrate pellets and 13.6 million tons of crude steel. Of

1806-510: Is followed by Japan and Korea, which consume a significant amount of raw iron ore and metallurgical coal . In 2006, China produced 588,000,000 t (579,000,000 long tons; 648,000,000 short tons) of iron ore, with an annual growth of 38%. Over the last 40 years, iron ore prices have been decided in closed-door negotiations between the small handful of miners and steelmakers which dominate both spot and contract markets. Until 2006, prices were determined in annual benchmark negotiations between

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1892-458: Is formed through the cooling and solidification of magma or lava . This magma may be derived from partial melts of pre-existing rocks in either a planet 's mantle or crust . Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Igneous rocks are divided into two main categories: Magmas tend to become richer in silica as they rise towards

1978-586: Is in the iron ranges around Lake Superior . These iron ranges occur in Minnesota and Michigan, which combined accounted for 93% of the usable iron ore produced in the United States in 2014. Seven of the nine operational open pit mines in the United States are located in Minnesota as well as two of the three tailings reclamation operations. The other two active open pit mines were located in Michigan . In 2016, one of

2064-693: 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 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

2150-488: Is more difficult to smelt than a haematite or other oxide ore. Driving off the carbonate as carbon dioxide requires more energy and so the ore 'kills' the blast furnace if added directly. Instead the ore must be given a preliminary roasting step. Developments of specific techniques to deal with these ores began in the early 19th century, largely with the work of Sir Thomas Lethbridge in Somerset . His 'Iron Mill' of 1838 used

2236-442: Is next in importance. About 65% of the Earth's crust by volume consists of igneous rocks. Of these, 66% are basalt and gabbro , 16% are granite, and 17% granodiorite and diorite . Only 0.6% are syenite and 0.3% are ultramafic . The oceanic crust is 99% basalt, which is an igneous rock of mafic composition. Granite and similar rocks, known as granitoids , dominate the continental crust . Sedimentary rocks are formed at

2322-645: Is often related to the depositional environment of the enclosing sediments. In addition, a number of recent studies have used the oxygen isotopic composition of sphaerosiderite (a type associated with soils ) as a proxy for the isotopic composition of meteoric water shortly after deposition. Although carbonate iron ores, such as siderite, have been economically important for steel production, they are far from ideal as an ore. Their hydrothermal mineralisation tends to form them as small ore lenses , often following steeply dipping bedding planes . This makes them not amenable to opencast working , and increases

2408-634: 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. 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 ". Metallic iron is virtually unknown on the Earth 's surface except as iron-nickel alloys from meteorites and very rare forms of deep mantle xenoliths . Although iron

2494-475: Is the Brazilian mining corporation Vale , followed by Australian companies Rio Tinto Group and BHP . A further Australian supplier, Fortescue Metals Group Ltd, 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 849,000,000 t (836,000,000 long tons; 936,000,000 short tons) in 2004. Australia and Brazil dominate

2580-418: 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, and smelting pure iron from these minerals would require a prohibitive amount of energy. Therefore, all sources of iron used by human industry exploit comparatively rarer iron oxide minerals, primarily hematite . Prehistoric societies used laterite as

2666-453: Is the study of Earth and its components, including the study of rock formations. Petrology is the study of the character and origin of rocks. Mineralogy is the study of the mineral components that create rocks. The study of rocks and their components has contributed to the geological understanding of Earth's history, the archaeological understanding of human history, and the development of engineering and technology in human society. While

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2752-422: 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. 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

2838-501: The Bessemer steel-making process . Although the first demonstrations by Bessemer in 1856 were successful, others' initial attempts to replicate his method infamously failed to produce good steel. Work by the metallurgist Robert Forester Mushet showed that the reason for the discrepancy was the nature of the Swedish ores that Bessemer had innocently used; they were very low in phosphorus. Using

2924-872: 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 9,602,000,000 t (9.450 × 10 long tons; 1.0584 × 10 short tons) of hematite and 3,408,000,000 t (3.354 × 10 long tons; 3.757 × 10 short tons) of magnetite . Chhattisgarh , Madhya Pradesh , Karnataka , Jharkhand , Odisha , Goa , Maharashtra , Andhra Pradesh , Kerala , Rajasthan , and Tamil Nadu are

3010-553: The Pilbara region of Western Australia is approximately 844,000,000 t (831,000,000 long tons; 930,000,000 short tons) per year and rising. Gavin Mudd ( RMIT University ) and Jonathon Law ( CSIRO ) expect it to be gone within 30–50 years and 56 years, respectively. These 2010 estimates require ongoing review to take into account shifting demand for lower-grade iron ore and improving mining and recovery techniques (allowing deeper mining below

3096-417: The history of geology includes many theories of rocks and their origins that have persisted throughout human history, the study of rocks was developed as a formal science during the 19th century. Plutonism was developed as a theory during this time, and the discovery of radioactive decay in 1896 allowed for the radiocarbon dating of rocks. Understanding of plate tectonics developed in the second half of

3182-405: The silicate mineral fragments will float and can be removed. Iron is the world's most commonly used metal—steel, of which iron ore is the key ingredient, represents almost 95% of all metal used per year. It is used primarily in structures, ships, automobiles, and machinery. Iron-rich rocks are common worldwide, but ore-grade commercial mining operations are dominated by the countries listed in

3268-420: The 13,600,000 t (13,400,000 long tons; 15,000,000 short tons) of steel 7,000,000 t (6,900,000 long tons; 7,700,000 short tons) was exported, and 43,100,000 t (42,400,000 long tons; 47,500,000 short tons) of iron ore was exported at a value of $ 4.6 billion. Of the iron ore exported, 38.5% of the volume was iron ore pellets with a value of $ 2.3 billion, and 61.5% was iron ore concentrates with

3354-399: The 20th century. Rocks are composed primarily of grains of minerals, which are crystalline solids formed from atoms chemically bonded into an orderly structure. Some rocks also contain mineraloids , which are rigid, mineral-like substances, such as volcanic glass , that lack crystalline structure. The types and abundance of minerals in a rock are determined by the manner in which it

3440-677: The 62–64% Fe range. Granite 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 . 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

3526-467: The Earth's surface, a process called magma differentiation . This occurs both because minerals low in silica crystallize out of the magma as it begins to cool ( Bowen's reaction series ) and because the magma assimilates some of the crustal rock through which it ascends ( country rock ), and crustal rock tends to be high in silica. Silica content is thus the most important chemical criterion for classifying igneous rock. The content of alkali metal oxides

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3612-503: The Earth's surface: temperatures greater than 150 to 200 °C and pressures greater than 1500 bars. This occurs, for example, when continental plates collide. Metamorphic rocks compose 27.4% of the crust by volume. The three major classes of metamorphic rock are based upon the formation mechanism. An intrusion of magma that heats the surrounding rock causes contact metamorphism—a temperature-dominated transformation. Pressure metamorphism occurs when sediments are buried deep under

3698-428: The United States is estimated to have accounted for 2% of the world's iron ore output. In the United States there are twelve iron ore mines, with nine being open pit mines and three being reclamation operations. There were also ten pelletizing plants, nine concentration plants, two direct-reduced iron (DRI) plants, and one iron nugget plant that were operating in 2014. In the United States the majority of iron ore mining

3784-411: 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

3870-523: The constituent particles, and particle size . These physical properties are the result of the processes that formed the rocks. Over the course of time, rocks can be transformed from one type into another, as described by a geological model called the rock cycle . This transformation produces three general classes of rock: igneous , sedimentary and metamorphic . Those three classes are subdivided into many groups. There are, however, no hard-and-fast boundaries between allied rocks. By increase or decrease in

3956-424: The cost of working them by mining with horizontal stopes . As the individual ore bodies are small, it may also be necessary to duplicate or relocate the pit head machinery, winding engine and pumping engine, between these bodies as each is worked out. This makes mining the ore an expensive proposition compared to typical ironstone or haematite opencasts. The recovered ore also has drawbacks. The carbonate ore

4042-523: The country's " economic demonstrated resources " of iron currently amount to 24 gigatonnes , or 24,000,000,000 t (2.4 × 10 long tons; 2.6 × 10 short tons). Another estimate places Australia's reserves of iron ore at 52,000,000,000 t (5.1 × 10 long tons; 5.7 × 10 short tons), or 30% of the world's estimated 170,000,000,000 t (1.7 × 10 long tons; 1.9 × 10 short tons), of which Western Australia accounts for 28,000,000,000 t (2.8 × 10 long tons; 3.1 × 10 short tons). The current production rate from

4128-584: The depletion of high-grade hematite ores in the United States, led after World War II to the development of lower-grade iron ore sources, principally the use of magnetite and taconite . 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 origin of iron can be ultimately traced to its formation through nuclear fusion in stars, and most of

4214-521: The development of metallurgy . Siderite Siderite has Mohs hardness of 3.75 to 4.25, a specific gravity of 3.96, a white streak and a vitreous lustre or pearly luster . Siderite is antiferromagnetic below its Néel temperature of 37 K (−236 °C) which can assist in its identification. It crystallizes in the trigonal crystal system , and are rhombohedral in shape, typically with curved and striated faces. It also occurs in masses. Color ranges from yellow to dark brown or black,

4300-491: The earliest humans. This early period, called the Stone Age , saw the development of many stone tools. Stone was then used as a major component in the construction of buildings and early infrastructure . Mining developed to extract rocks from the Earth and obtain the minerals within them, including metals . Modern technology has allowed the development of new human-made rocks and rock-like substances, such as concrete . Geology

4386-606: The earth's surface by the accumulation and cementation of fragments of earlier rocks, minerals, and organisms or as chemical precipitates and organic growths in water ( sedimentation ). This process causes clastic sediments (pieces of rock) or organic particles ( detritus ) to settle and accumulate or for minerals to chemically precipitate ( evaporite ) from a solution . The particulate matter then undergoes compaction and cementation at moderate temperatures and pressures ( diagenesis ). Before being deposited, sediments are formed by weathering of earlier rocks by erosion in

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4472-427: The earth, from an ore body, vein or seam . The term also includes the removal of soil. Materials recovered by mining include base metals , precious metals , iron , uranium , coal , diamonds , limestone , oil shale , rock salt , potash , construction aggregate and dimension stone . Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in

4558-474: The form of a previously obscure ferromanganese ore with no phosphorus, spiegeleisen . This created a sudden demand for spiegeleisen. Although it was not available in sufficient quantity as a mineral, steelworks such as that at Ebbw Vale in South Wales soon learned to make it from the spathic siderite ores. For a few decades, spathic ores were therefore in demand and this encouraged their mining. In time though,

4644-442: 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 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

4730-402: The ground; pressure is dominant, and temperature plays a smaller role. This is termed burial metamorphism, and it can result in rocks such as jade . Where both heat and pressure play a role, the mechanism is termed regional metamorphism. This is typically found in mountain-building regions. Depending on the structure, metamorphic rocks are divided into two general categories. Those that possess

4816-788: The groundwater table). Brazil is the second-largest producer of iron ore after Australia, accounting for 16% of the world's iron ore production. After a somewhat sluggish production volume 2010-2020, partly due to the Mariana dam disaster in 2015 and the Brumadinho dam disaster in 2019, which halted the production at the two involved mines, production has increased steadily since 2021, when Brazil produced 431,000,000 t (424,000,000 long tons; 475,000,000 short tons). In 2022 it increased to 435,000,000 t (428,000,000 long tons; 480,000,000 short tons) and in 2023 to 440,000,000 t (430,000,000 long tons; 490,000,000 short tons). The Brazilian production

4902-450: The iron and carbon smelting must be kept in an oxygen-deficient (reducing) state to promote the burning of carbon to produce CO and not CO 2 . 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

4988-413: 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. Carbon monoxide is the primary ingredient of chemically stripping oxygen from iron. Thus,

5074-887: The iron is thought to have originated in dying stars that are large enough to explode as supernovae . The Earth's core is thought to consist mainly of iron, but this is inaccessible from the surface. Some iron meteorites are thought to have originated from asteroids 1,000 km (620 mi) in diameter or larger. 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

5160-491: The kind of metals available from the rock of a region. Anthropic rock is synthetic or restructured rock formed by human activity. Concrete is recognized as a human-made rock constituted of natural and processed rock and having been developed since Ancient Rome . Rock can also be modified with other substances to develop new forms, such as epoxy granite . Artificial stone has also been developed, such as Coade stone . Geologist James R. Underwood has proposed anthropic rock as

5246-431: The land to prepare it for other uses once mining ceases. Mining processes may create negative impacts on the environment both during the mining operations and for years after mining has ceased. These potential impacts have led to most of the world's nations adopting regulations to manage negative effects of mining operations. Stone tools have been used for millions of years by humans and earlier hominids . The Stone Age

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5332-446: The latter being due to the presence of manganese. Siderite is commonly found in hydrothermal veins , and is associated with barite , fluorite , galena , and others. It is also a common diagenetic mineral in shales and sandstones , where it sometimes forms concretions , which can encase three-dimensionally preserved fossils . In sedimentary rocks , siderite commonly forms at shallow burial depths and its elemental composition

5418-423: 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

5504-476: 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

5590-423: The main iron ore producers ( BHP Billiton , Rio Tinto , and Vale S.A. ) and Japanese importers. In 2006, Chinese company Baosteel began handling negotiations for the importer side. The Chinese government replaced Baosteel with China Iron and Steel Association as lead negotiator in 2009. Traditionally, the first deal reached between these the major producers and the major importers sets a benchmark to be followed by

5676-405: 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

5762-399: The original 'acidic' liner of the Bessemer converter, made from siliceous sandstone or ganister , was replaced by a 'basic' liner in the newer Gilchrist Thomas process . This removed the phosphorus impurities as slag produced by chemical reaction with the liner, and no longer required spiegeleisen. From the 1880s demand for the ores fell once again and many of their mines, including those of

5848-418: The original rock was formed. This process is called metamorphism , meaning to "change in form". The result is a profound change in physical properties and chemistry of the stone. The original rock, known as the protolith , transforms into other mineral types or other forms of the same minerals, by recrystallization . The temperatures and pressures required for this process are always higher than those found at

5934-425: The particles of clastic sedimentary rocks can be further classified by grain size . The smallest sediments are clay , followed by silt , sand , and gravel . Some systems include cobbles and boulders as measurements. Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which

6020-504: 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

6106-471: 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 be 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

6192-473: 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

6278-462: The proportions of their minerals, they pass through gradations from one to the other; the distinctive structures of one kind of rock may thus be traced, gradually merging into those of another. Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series. Igneous rock (derived from the Latin word igneus, meaning of fire, from ignis meaning fire)

6364-429: 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 32 and 45 μm (0.0013 and 0.0018 in) in order to produce a low-silica magnetite concentrate. Magnetite concentrate grades are generally in excess of 70% iron by weight and usually are low in phosphorus, aluminium, titanium, and silica and demand

6450-651: The rest of the industry. Singapore Mercantile Exchange (SMX) has launched the world's first global iron ore futures contract, based on the Metal Bulletin Iron Ore Index (MBIOI) which uses daily price data from a broad spectrum of industry participants and independent Chinese steel consultancy and data provider Shanghai Steelhome's widespread contact base of steel producers and iron ore traders across China. The futures contract has seen monthly volumes over 1,500,000 t (1,500,000 long tons; 1,700,000 short tons) after eight months of trading. This move follows

6536-407: 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

6622-641: The rocks of other celestial objects. Rocks are usually grouped into three main groups: igneous rocks , sedimentary rocks and metamorphic rocks . Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis and lithification of sediments , which in turn are formed by the weathering , transport, and deposition of existing rocks. Metamorphic rocks are formed when existing rocks are subjected to such high pressures and temperatures that they are transformed without significant melting. Humanity has made use of rocks since

6708-444: 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 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 ,

6794-458: The seventh largest global center of iron ore production, behind Australia, Brazil, China, India, Russia, and South Africa. Producers of iron ore in Ukraine include Ferrexpo , Metinvest , and ArcelorMittal Kryvyi Rih . In 2014, mines in the United States produced 57,500,000 t (56,600,000 long tons; 63,400,000 short tons) of iron ore with an estimated value of $ 5.1 billion. Iron mining in

6880-449: The seventh-largest global center of iron ore production, behind Australia, Brazil, China, Russia, South Africa, and Ukraine. India's iron ore production in 2023 was 285,000,000 metric tonnes and was the fourth largest producer in the world. According to the U.S. Geological Survey's 2021 Report on iron ore, Ukraine is estimated to have produced 62,000,000 t (61,000,000 long tons; 68,000,000 short tons) of iron ore in 2020, placing it as

6966-401: 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. Mining iron ore

7052-586: The two mines shut down. There have also been iron ore mines in Utah and Alabama ; however, the last iron ore mine in Utah shut down in 2014 and the last iron ore mine in Alabama shut down in 1975. Iron ores consist 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

7138-610: The universe's celestial bodies. In the Solar System , Mars , Venus , and Mercury are composed of rock, as are many natural satellites , asteroids , and meteoroids . Meteorites that fall to Earth provide evidence of extraterrestrial rocks and their composition. They are typically heavier than rocks on Earth. Asteroid rocks can also be brought to Earth through space missions, such as the Hayabusa mission. Lunar rocks and Martian rocks have also been studied. The use of rock has had

7224-408: Was a period of widespread stone tool usage. Early Stone Age tools were simple implements, such as hammerstones and sharp flakes. Middle Stone Age tools featured sharpened points to be used as projectile points , awls, or scrapers . Late Stone Age tools were developed with craftsmanship and distinct cultural identities. Stone tools were largely superseded by copper and bronze tools following

7310-456: Was formed. Most rocks contain silicate minerals , compounds that include silica tetrahedra in their crystal lattice , and account for about one-third of all known mineral species and about 95% of the earth's crust . The proportion of silica in rocks and minerals is a major factor in determining their names and properties. Rocks are classified according to characteristics such as mineral and chemical composition, permeability , texture of

7396-760: Was quarried for construction as early as 4000 BCE in Egypt, and stone was used to build fortifications in Inner Mongolia as early as 2800 BCE. The soft rock, tuff , is common in Italy, and the Romans used it for many buildings and bridges. Limestone was widely used in construction in the Middle Ages in Europe and remained popular into the 20th century. Mining is the extraction of valuable minerals or other geological materials from

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