Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. [1] [2] [3] The grade of ore refers to the concentration of the desired material it contains. The value of the metals or minerals a rock contains must be weighed against the cost of extraction to determine whether it is of sufficiently high grade to be worth mining and is therefore considered an ore. [4] A complex ore is one containing more than one valuable mineral. [5]
Minerals of interest are generally oxides, sulfides, silicates, or native metals such as copper or gold. [5] Ore bodies are formed by a variety of geological processes generally referred to as ore genesis and can be classified based on their deposit type. Ore is extracted from the earth through mining and treated or refined, often via smelting, to extract the valuable metals or minerals. [4] Some ores, depending on their composition, may pose threats to health or surrounding ecosystems.
The word ore is of Anglo-Saxon origin, meaning lump of metal. [6]
In most cases, an ore does not consist entirely of a single mineral, but it is mixed with other valuable minerals and with unwanted or valueless rocks and minerals. The part of an ore that is not economically desirable and that cannot be avoided in mining is known as gangue. [2] [3] The valuable ore minerals are separated from the gangue minerals by froth flotation, gravity concentration, electric or magnetic methods, and other operations known collectively as mineral processing [5] [7] or ore dressing. [8]
Mineral processing consists of first liberation, to free the ore from the gangue, and concentration to separate the desired mineral(s) from it. [5] Once processed, the gangue is known as tailings, which are useless but potentially harmful materials produced in great quantity, especially from lower grade deposits. [5]
An ore deposit is an economically significant accumulation of minerals within a host rock. [9] This is distinct from a mineral resource in that it is a mineral deposit occurring in high enough concentration to be economically viable. [4] An ore deposit is one occurrence of a particular ore type. [10] Most ore deposits are named according to their location, or after a discoverer (e.g. the Kambalda nickel shoots are named after drillers), [11] or after some whimsy, a historical figure, a prominent person, a city or town from which the owner came, something from mythology (such as the name of a god or goddess) [12] or the code name of the resource company which found it (e.g. MKD-5 was the in-house name for the Mount Keith nickel sulphide deposit). [13]
Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis. The following is a general categorization of the main ore deposit types:
Magmatic deposits are ones who originate directly from magma
These are ore deposits which form as a direct result of metamorphism.
These are the leading source of copper ore. [27] [28] Porphyry copper deposits form along convergent boundaries and are thought to originate from the partial melting of subducted oceanic plates and subsequent concentration of Cu, driven by oxidation. [28] [29] These are large, round, disseminated deposits containing on average 0.8% copper by weight. [5]
Hydrothermal
Hydrothermal deposits are a large source of ore. They form as a result of the precipitation of dissolved ore constituents out of fluids. [1] [30]
Laterites form from the weathering of highly mafic rock near the equator. They can form in as little as one million years and are a source of iron (Fe), manganese (Mn), and aluminum (Al). [35] They may also be a source of nickel and cobalt when the parent rock is enriched in these elements. [36]
Banded iron formations (BIFs) are the highest concentration of any single metal available. [1] They are composed of chert beds alternating between high and low iron concentrations. [37] Their deposition occurred early in Earth's history when the atmospheric composition was significantly different from today. Iron rich water is thought to have upwelled where it oxidized to Fe (III) in the presence of early photosynthetic plankton producing oxygen. This iron then precipitated out and deposited on the ocean floor. The banding is thought to be a result of changing plankton population. [38] [39]
Sediment Hosted Copper forms from the precipitation of a copper rich oxidized brine into sedimentary rocks. These are a source of copper primarily in the form of copper-sulfide minerals. [40] [41]
Placer deposits are the result of weathering, transport, and subsequent concentration of a valuable mineral via water or wind. They are typically sources of gold (Au), platinum group elements (PGE), sulfide minerals, tin (Sn), tungsten (W), and rare-earth elements (REEs). A placer deposit is considered alluvial if formed via river, colluvial if by gravity, and eluvial when close to their parent rock. [42] [43]
Polymetallic nodules, also called manganese nodules, are mineral concretions on the sea floor formed of concentric layers of iron and manganese hydroxides around a core. [44] They are formed by a combination of diagenetic and sedimentary precipitation at the estimated rate of about a centimeter over several million years. [45] The average diameter of a polymetallic nodule is between 3 and 10 cm (1 and 4 in) in diameter and are characterized by enrichment in iron, manganese, heavy metals, and rare earth element content when compared to the Earth's crust and surrounding sediment. The proposed mining of these nodules via remotely operated ocean floor trawling robots has raised a number of ecological concerns. [46]
The extraction of ore deposits generally follows these steps. [4] Progression from stages 1–3 will see a continuous disqualification of potential ore bodies as more information is obtained on their viability: [47]
With rates of ore discovery in a steady decline since the mid 20th century, it is thought that most surface level, easily accessible sources have been exhausted. This means progressively lower grade deposits must be turned to, and new methods of extraction must be developed. [1]
Some ores contain heavy metals, toxins, radioactive isotopes and other potentially negative compounds which may pose a risk to the environment or health. The exact effects an ore and its tailings have is dependent on the minerals present. Tailings of particular concern are those of older mines, as containment and remediation methods in the past were next to non-existent, leading to high levels of leaching into the surrounding environment. [5] Mercury and arsenic are two ore related elements of particular concern. [51] Additional elements found in ore which may have adverse health affects in organisms include iron, lead, uranium, zinc, silicon, titanium, sulfur, nitrogen, platinum, and chromium. [52] Exposure to these elements may result in respiratory and cardiovascular problems and neurological issues. [52] These are of particular danger to aquatic life if dissolved in water. [5] Ores such as those of sulphide minerals may severely increase the acidity of their immediate surroundings and of water, with numerous, long lasting impacts on ecosystems. [5] [53] When water becomes contaminated it may transport these compounds far from the tailings site, greatly increasing the affected range. [52]
Uranium ores and those containing other radioactive elements may pose a significant threat if leaving occurs and isotope concentration increases above background levels. Radiation can have severe, long lasting environmental impacts and cause irreversible damage to living organisms. [54]
Metallurgy began with the direct working of native metals such as gold, lead and copper. [55] Placer deposits, for example, would have been the first source of native gold. [6] The first exploited ores were copper oxides such as malachite and azurite, over 7000 years ago at Çatalhöyük . [56] [57] [58] These were the easiest to work, with relatively limited mining and basic requirements for smelting. [55] [58] It is believed they were once much more abundant on the surface than today. [58] After this, copper sulphides would have been turned to as oxide resources depleted and the Bronze Age progressed. [55] [59] Lead production from galena smelting may have been occurring at this time as well. [6]
The smelting of arsenic-copper sulphides would have produced the first bronze alloys. [56] The majority of bronze creation however required tin, and thus the exploitation of cassiterite, the main tin source, began. [56] Some 3000 years ago, the smelting of iron ores began in Mesopotamia. Iron oxide is quite abundant on the surface and forms from a variety of processes. [6]
Until the 18th century gold, copper, lead, iron, silver, tin, arsenic and mercury were the only metals mined and used. [6] In recent decades, Rare Earth Elements have been increasingly exploited for various high-tech applications. [60] This has led to an ever-growing search for REE ore and novel ways of extracting said elements. [60] [61]
Ores (metals) are traded internationally and comprise a sizeable portion of international trade in raw materials both in value and volume. This is because the worldwide distribution of ores is unequal and dislocated from locations of peak demand and from smelting infrastructure.
Most base metals (copper, lead, zinc, nickel) are traded internationally on the London Metal Exchange, with smaller stockpiles and metals exchanges monitored by the COMEX and NYMEX exchanges in the United States and the Shanghai Futures Exchange in China. The global Chromium market is currently dominated by the United States and China. [62]
Iron ore is traded between customer and producer, though various benchmark prices are set quarterly between the major mining conglomerates and the major consumers, and this sets the stage for smaller participants.
Other, lesser, commodities do not have international clearing houses and benchmark prices, with most prices negotiated between suppliers and customers one-on-one. This generally makes determining the price of ores of this nature opaque and difficult. Such metals include lithium, niobium-tantalum, bismuth, antimony and rare earths. Most of these commodities are also dominated by one or two major suppliers with >60% of the world's reserves. China is currently leading in world production of Rare Earth Elements. [63]
The World Bank reports that China was the top importer of ores and metals in 2005 followed by the US and Japan. [64]
For detailed petrographic descriptions of ore minerals see Tables for the Determination of Common Opaque Minerals by Spry and Gedlinske (1987). [65] Below are the major economic ore minerals and their deposits, grouped by primary elements.
Type | Mineral | Symbol/formula | Uses | Source(s) | Ref |
---|---|---|---|---|---|
Metal ore minerals | Aluminum | Al | Alloys, conductive materials, lightweight applications | Gibbsite (Al(OH)3) and aluminium hydroxide oxide, which are found in laterites. Also Bauxite and Barite | [5] ' |
Antimony | Sb | Alloys, flame retardation | Stibnite (Sb2S3) | [5] | |
Beryllium | Be | Metal alloys, in the nuclear industry, in electronics | Beryl (Be3Al2Si6O18), found in granitic pegmatites | [5] | |
Bismuth | Bi | Alloys, pharmeceuticals | Native bismuth and bismuthinite (Bi2S3) with sulphide ores | [5] | |
Cesium | Cs | Photoelectrics, pharmaceuticals | Lepidolite (K(Li, Al)3 (Si, Al)4O10 (OH,F)2) from pegmatites | [5] | |
Chromium | Cr | Alloys, electroplating, colouring agents | Chromite (FeCr2O4) from stratiform and podiform chromitites | [5] [19] [21] | |
Cobalt | Co | Alloys, chemical catalysts, cemented carbide | Smaltite (CoAs2) in veins with cobaltite; silver, nickel and calcite; cobaltite (CoAsS) in veins with smaltite, silver, nickel and calcite; carrollite (CuCo2S4) and linnaeite (Co3S4) as constituents of copper ore; and linnaeite | ||
Copper | Cu | Alloys, high conductivity, corrosion resistance | Sulphide minerals, including chalcopyrite (CuFeS2; primary ore mineral) in sulphide deposits, or porphyry copper deposits; covellite (CuS); chalcocite (Cu2S; secondary with other sulphide minerals) with native copper and cuprite deposits and bornite (Cu5FeS4; secondary with other sulphide minerals) Oxidized minerals, including malachite (Cu2CO3(OH)2) in the oxidized zone of copper deposits; cuprite (Cu2O; secondary mineral ); and azurite (Cu3(CO3)2(OH)2; secondary) | [5] [6] [28] [55] | |
Gold | Au | Electronics, jewellery, dentistry | Placer deposits, quartz grains | [5] [42] [1] [66] [33] [43] | |
Iron | Fe | Industry use, construction, steel | Hematite (Fe2O3; primary source) in banded iron formations, veins, and igneous rock; magnetite (Fe3O4) in igneous and metamorphic rocks; goethite (FeO(OH); secondary to hematite); limonite (FeO(OH)nH2O; secondary to hematite) | [5] [1] [67] | |
Lead | Pb | Alloys, pigmentation, batteries, corrosion resistance, radiation shielding | Galena (PbS) in veins with other sulphide materials and in pegmatites; cerussite (PbCO3) in oxidized lead zones along with galena | [5] [6] [31] | |
Lithium | Li | Metal production, batteries, ceramics | Spodumene (LiAlSi2O6) in pegmatites | [5] | |
Manganese | Mn | Steel alloys, chemical manufacturing | Pyrolusite (MnO2) in oxidized manganese zones like laterites and skarns; manganite (MnO(OH)) and braunite (3Mn2O3 MnSiO3) with pyrolusite | [5] [23] [35] | |
Mercury | Hg | Scientific instruments, electrical applications, paint, solvent, pharmeceuticals | Cinnabar (HgS) in sedimentary fractures with other sulphide minerals | [5] [6] | |
Molybdenum | Mo | Alloys, electronics, industry | Molybdenite (MoS2) in porphyry deposits, powellite (CaMoO4) in hydrothermal deposits | [5] | |
Nickel | Ni | Alloys, food and pharmaceutical applications, corrosion resistance | Pentlandite (Fe,Ni)9S8 with other sulphide minerals; garnierite (NiMg) with chromite and in laterites; niccolite (NiAs) in magmatic sulphide deposits | [5] [16] | |
Niobium | Nb | Alloys, corrosion resistance | Pyrochlore (Na,Ca)2Nb2O6(OH,F) and columbite ((Fe II,Mn II)Nb 2 O 6) in granitic pegmatites | [5] | |
Platinum Group | Pt | Dentistry, jewelry, chemical applications, corrosion resistance, electronics | With chromite and copper ore, in placer deposits; sperrylite (PtAs2) in sulphide deposits and gold veins | [5] [68] | |
Rare-earth elements | La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y | Permanent magnets, batteries, glass treatment, petroleum industry, micro-electronics, alloys, nuclear applications, corrosion protection (La and Ce are the most widely applicable) | Bastnäsite (REECO3F; for Ce, La, Pr, Nd) in carbonatites; monazite (REEPO4; for La, Ce, Pr, Nd) in placer deposits; xenotime (YPO4; for Y) in pegmatites; eudialyte (Na15Ca6(Fe,Mn)3Zr3SiO(O,OH,H2O)3 (Si3O9)2(Si9O27)2(OH,Cl)2) in igneous rocks; allanite ((REE,Ca,Y)2(Al,Fe2+,Fe3+)3(SiO4)3(OH)) in pegmatites and carbonatites | [5] [15] [60] [69] [63] | |
Rhenium | Re | Catalyst, temperature applications | Molybdenite (MoS2) in porphyry deposits | [5] [70] | |
Silver | Ag | Jewellery, glass, photo-electric applications, batteries | Sulfide deposits; Argentite (Ag2S; secondary to copper, lead and zinc ores) | [5] [71] | |
Tin | Sn | Solder, bronze, cans, pewter | Cassiterite (SnO2) in placer and magmatic deposits | [5] [56] | |
Titanium | Ti | Aerospace, industrial tubing | Ilmenite (FeTiO3) and rutile (TiO2) economically sourced from placer deposits with REEs | [5] [72] | |
Tungsten | W | Filaments, electronics, lighting | Wolframite ((Fe,Mn)WO4) and scheelite (CaWO4) in skarns and in porphyry along with sulphide minerals | [5] [73] | |
Uranium | U | Nuclear fuel, ammunition, radiation shielding | Pitchblende (UO2) in uraninite placer deposits; carnotite (K2(UO2)2(VO4)2 3H2O) in placer deposits | [5] [74] | |
Vanadium | V | Alloys, catalysts, glass colouring, batteries | Patronite (VS4) with sulphide minerals; roscoelite (K(V,Al,Mg)2 AlSi3O10(OH)2) in epithermal gold deposits | [5] [75] | |
Zinc | Zn | Corrosion protection, alloys, various industrial compounds | Sphalerite ((Zn,Fe)S) with other sulphide minerals in vein deposits; smithsonite (ZnCO3) in oxidized zone of zinc bearing sulphide deposits | [5] [6] [31] | |
Zirconium | Zr | Alloys, nuclear reactors, corrosion resistance | Zircon (ZrSiO4) in igneous rocks and in placers | [5] [76] | |
Non-metal ore minerals | Fluorospar | CaF2 | Steelmaking, optical equipment | Hydrothermal veins and pegmatites | [5] [77] |
Graphite | C | Lubricant, industrial molds, paint | Pegmatites and metamorphic rocks | [5] | |
Gypsum | CaSO42H2O | Fertilizer, filler, cement, pharmaceuticals, textiles | Evaporites; VMS | [5] [78] | |
Diamond | C | Cutting, jewelry | Kimberlites | [5] [22] | |
Feldspar | Fsp | Ceramics, glassmaking, glazes | Orthoclase (KAlSi3O8) and albite (NaAlSi3O8) are ubiquitous throughout Earth's crust | [5] |
Bioleaching is the extraction or liberation of metals from their ores through the use of living organisms. Bioleaching is one of several applications within biohydrometallurgy and several methods are used to treat ores or concentrates containing copper, zinc, lead, arsenic, antimony, nickel, molybdenum, gold, silver, and cobalt.
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 (Fe
2O
3, 69.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH)·n(H2O), 55% Fe), or siderite (FeCO3, 48.2% Fe).
Pentlandite is an iron–nickel sulfide with the chemical formula (Fe,Ni)9S8. Pentlandite has a narrow variation range in nickel to iron ratios (Ni:Fe), but it is usually described as 1:1. In some cases, this ratio is skewed by the presence of pyrrhotite inclusions. It also contains minor cobalt, usually at low levels as a fraction of weight.
Chalcopyrite ( KAL-kə-PY-ryte, -koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.
Sphalerite is a sulfide mineral with the chemical formula (Zn, Fe)S. It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Valley type, and volcanogenic massive sulfide deposits. It is found in association with galena, chalcopyrite, pyrite, calcite, dolomite, quartz, rhodochrosite, and fluorite.
The platinum-group metals (PGMs), also known as the platinoids, platinides, platidises, platinum group, platinum metals, platinum family or platinum-group elements (PGEs), are six noble, precious metallic elements clustered together in the periodic table. These elements are all transition metals in the d-block.
Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, bimetasomatic reaction of different lithologies, and infiltration metasomatism by magmatic-hydrothermal fluids. Skarns tend to be rich in calcium-magnesium-iron-manganese-aluminium silicate minerals, which are also referred to as calc-silicate minerals. These minerals form as a result of alteration which occurs when hydrothermal fluids interact with a protolith of either igneous or sedimentary origin. In many cases, skarns are associated with the intrusion of a granitic pluton found in and around faults or shear zones that commonly intrude into a carbonate layer composed of either dolomite or limestone. Skarns can form by regional or contact metamorphism and therefore form in relatively high temperature environments. The hydrothermal fluids associated with the metasomatic processes can originate from a variety of sources; magmatic, metamorphic, meteoric, marine, or even a mix of these. The resulting skarn may consist of a variety of different minerals which are highly dependent on both the original composition of the hydrothermal fluid and the original composition of the protolith.
Copper extraction refers to the methods used to obtain copper from its ores. The conversion of copper ores consists of a series of physical, chemical, and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors.
The Río Tinto is a highly toxic river in southwestern Spain that rises in the Sierra Morena mountains of Andalusia. It flows generally south-southwest, reaching the Gulf of Cádiz at Huelva. The Rio Tinto river has a unique red and orange colour derived from its chemical makeup that is extremely acidic and with very high levels of iron and heavy metals.
The Bushveld Igneous Complex (BIC) is the largest layered igneous intrusion within the Earth's crust. It has been tilted and eroded forming the outcrops around what appears to be the edge of a great geological basin: the Transvaal Basin. It is approximately two billion years old and is divided into four limbs: northern, eastern, southern and western. It comprises the Rustenburg Layered suite, the Lebowa Granites and the Rooiberg Felsics, that are overlain by the Karoo sediments. The site was first publicised around 1897 by Gustaaf Molengraaff who found the native South African tribes residing in and around the area.
The Great Dyke or Dike is a linear geological feature that trends nearly north-south through the centre of Zimbabwe passing just to the west of the capital, Harare. It consists of a band of short, narrow ridges and hills spanning for approximately 550 kilometres (340 mi). The hills become taller as the range goes north, and reach up to 460 metres (1,510 ft) above the Mvurwi Range. The range is host to vast ore deposits, including gold, silver, chromium, platinum, nickel and asbestos.
Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
A layered intrusion is a large sill-like body of igneous rock which exhibits vertical layering or differences in composition and texture. These intrusions can be many kilometres in area covering from around 100 km2 (39 sq mi) to over 50,000 km2 (19,000 sq mi) and several hundred metres to over one kilometre (3,300 ft) in thickness. While most layered intrusions are Archean to Proterozoic in age, they may be any age such as the Cenozoic Skaergaard intrusion of east Greenland or the Rum layered intrusion in Scotland. Although most are ultramafic to mafic in composition, the Ilimaussaq intrusive complex of Greenland is an alkalic intrusion.
Kambalda type komatiitic nickel ore deposits are a class of magmatic iron-nickel-copper-platinum-group element ore deposit in which the physical processes of komatiite volcanology serve to deposit, concentrate and enrich a Fe-Ni-Cu-(PGE) sulfide melt within the lava flow environment of an erupting komatiite volcano.
Creighton Mine is an underground nickel, copper, and platinum-group elements (PGE) mine. It is presently owned and operated by Vale Limited in the city of Greater Sudbury, Ontario, Canada. Open pit mining began in 1901, and underground mining began in 1906. The mine is situated in the Sudbury Igneous Complex (SIC) in its South Range geologic unit. The mine is the source of many excavation-related seismic events, such as earthquakes and rock burst events. It is home to SNOLAB, and is currently the deepest nickel mine in Canada. Expansion projects to deepen the Creighton Mine are currently underway.
Cubanite is a copper iron sulfide mineral that commonly occurs as a minor alteration mineral in magmatic sulfide deposits. It has the chemical formula CuFe2S3 and when found, it has a bronze to brass-yellow appearance. On the Mohs hardness scale, cubanite falls between 3.5 and 4 and has a orthorhombic crystal system. Cubanite is chemically similar to chalcopyrite; however, it is the less common copper iron sulfide mineral due to crystallization requirements.
Iron oxide copper gold ore deposits (IOCG) are important and highly valuable concentrations of copper, gold and uranium ores hosted within iron oxide dominant gangue assemblages which share a common genetic origin.
Carl Michael Lesher is an American geologist. He is an authority on the geology and origin of nickel-copper-platinum group element deposits, especially those associated with komatiites, their physical volcanology and localization, the geochemistry and petrology of associated rocks, and controls on their composition.
Hydrothermal mineral deposits are accumulations of valuable minerals which formed from hot waters circulating in Earth's crust through fractures. They eventually produce metallic-rich fluids concentrated in a selected volume of rock, which become supersaturated and then precipitate ore minerals. In some occurrences, minerals can be extracted for a profit by mining. Discovery of mineral deposits consumes considerable time and resources and only about one in every one thousand prospects explored by companies are eventually developed into a mine. A mineral deposit is any geologically significant concentration of an economically useful rock or mineral present in a specified area. The presence of a known but unexploited mineral deposit implies a lack of evidence for profitable extraction.
An orogenic gold deposit is a type of hydrothermal mineral deposit. More than 75% of the gold recovered by humans through history belongs to the class of orogenic gold deposits. Rock structure is the primary control of orogenic gold mineralization at all scales, as it controls both the transport and deposition processes of the mineralized fluids, creating structural pathways of high permeability and focusing deposition to structurally controlled locations.
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