Ore

Last updated
Iron ore (banded iron formation) Banded iron formation.png
Iron ore (banded iron formation)
Iron ore (Banded iron formation, Minnesota) consisting of magnetite as main ore mineral (silver-grey bands) and quartz as main gangue mineral (light and red bands). The red bands contain also hematite; most of it, otherwise a valuable iron ore mineral, cannot be recovered economically because it is finely intergrown with quartz Jaspilite banded iron formation (Soudan Iron-Formation, Neoarchean, ~2.69 Ga; Stuntz Bay Road outcrop, Soudan Underground State Park, Soudan, Minnesota, USA) 20 (19219005412).jpg
Iron ore (Banded iron formation, Minnesota) consisting of magnetite as main ore mineral (silver-grey bands) and quartz as main gangue mineral (light and red bands). The red bands contain also hematite; most of it, otherwise a valuable iron ore mineral, cannot be recovered economically because it is finely intergrown with quartz
Manganese ore - psilomelane (size: 6.7 x 5.8 x 5.1 cm) Psilomelane-167850.jpg
Manganese ore psilomelane (size: 6.7 × 5.8 × 5.1 cm)
Lead ore - galena and anglesite (size: 4.8 x 4.0 x 3.0 cm) Anglesite-Galena-249200.jpg
Lead ore galena and anglesite (size: 4.8 × 4.0 × 3.0 cm)
Gold ore (size: 7.5 x 6.1 x 4.1 cm) Gold-Quartz-273364.jpg
Gold ore (size: 7.5 × 6.1 × 4.1 cm)
Minecart on display at the Historic Archive and Museum of Mining in Pachuca, Mexico OreCartPachuca.JPG
Minecart on display at the Historic Archive and Museum of Mining in Pachuca, Mexico

Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit. [1] [2] Ore is extracted from the earth through mining and treated or refined, often via smelting, to extract the valuable metals or minerals. [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. [3]

Contents

Minerals of interest are generally oxides, sulfides, silicates, or native metals such as copper or gold. Ores must be processed to extract the elements of interest from the waste rock. Ore bodies are formed by a variety of geological processes generally referred to as ore genesis.

Ore, gangue, ore minerals, gangue minerals

In most cases, an ore does not consist entirely of a single ore 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 can not be avoided in mining is known as gangue. [1] [2] The valuable ore minerals are separated from the gangue minerals by froth flotation, gravity concentration, and other operations known collectively as mineral processing, or ore dressing.

Ore deposits

An ore deposit is an economically significant accumulation of minerals within a host rock. This is distinct from a mineral resource as defined by the mineral resource classification criteria. An ore deposit is one occurrence of a particular ore type. Most ore deposits are named according to their location (for example, the Witwatersrand, South Africa), or after a discoverer (e.g. the Kambalda nickel shoots are named after drillers), or after some whimsy, a historical figure, a prominent person, something from mythology (phoenix, kraken, serepentleopard, etc.) 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).

Classification

Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis. The classifications below are typical.

Hydrothermal epigenetic deposits

Magmatic deposits

A cross-section of a typical volcanogenic massive sulfide (VMS) ore deposit Classic VMS Deposit2.png
A cross-section of a typical volcanogenic massive sulfide (VMS) ore deposit

Metamorphically reworked deposits

Sedimentary deposits

Magnified view of banded iron formation specimen from Upper Michigan. Scale bar is 5.0 mm. MichiganBIF.jpg
Magnified view of banded iron formation specimen from Upper Michigan. Scale bar is 5.0 mm.

Hydrothermal deposits formed largely from basinal brines

Hydrothermal deposits formed by basinal saline fluids, include the following main groups: [4]

Extraction

Some ore deposits in the world Simplified world mining map 1.png
Some ore deposits in the world
Some additional ore deposits in the world Simplified world mining map 2.png
Some additional ore deposits in the world

The basic extraction of ore deposits follows these steps:

  1. Prospecting or exploration to find and then define the extent and value of ore where it is located ("ore body").
  2. Conduct resource estimation to mathematically estimate the size and grade of the deposit.
  3. Conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work.
  4. Conduct a feasibility study to evaluate the financial viability, technical and financial risks and robustness of the project and make a decision as whether to develop or walk away from a proposed mine project. This includes mine planning to evaluate the economically recoverable portion of the deposit, the metallurgy and ore recoverability, marketability and payability of the ore concentrates, engineering, milling and infrastructure costs, finance and equity requirements and a cradle to grave analysis of the possible mine, from the initial excavation all the way through to reclamation.
  5. Development of access to an ore body and building of mine plant and equipment.
  6. The operation of the mine in an active sense.
  7. Reclamation to make land where a mine had been suitable for future use.

Trade

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.

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. The London Metal Exchange aims to add uranium to its list of metals on warrant.

The World Bank reports that China was the top importer of ores and metals in 2005 followed by the US and Japan. [7] [ citation needed ]

Important ore minerals

See also

Related Research Articles

Bioleaching is the extraction of metals from their ores through the use of living organisms. This is much cleaner than the traditional heap leaching using cyanide. Bioleaching is one of several applications within biohydrometallurgy and several methods are used to recover copper, zinc, lead, arsenic, antimony, nickel, molybdenum, gold, silver, and cobalt.

Iron ore Ore rich in iron or the element Fe

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(H2O), 55% Fe) or siderite (FeCO3, 48.2% Fe).

Chalcopyrite Copper iron sulfide mineral

Chalcopyrite ( KAL-ko-PY-ryt) 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

Sphalerite ( S) is a mineral and ore of zinc. When the iron content is high, sphalerite is an opaque black variety called marmatite. It was discovered in 1847 by Ernst Friedrich Glocker, who named it based on the Greek work "sphaleros" meaning deceiving due to sphalerite being hard to identify. Sphalerite is found in association with galena, chalcopyrite, pyrite, calcite, dolomite, quartz, rhodochrosite and fluorite. Miners have been known to refer to sphalerite as zinc blende, black-jack and ruby blende. 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 used for zinc, brass, bronze, gemstones, galvanization, pharmaceuticals and cosmetics.

Skarn Hard, coarse-grained, hydrothermally altered metamorphic rocks

Skarns or tactites are hard, coarse-grained metamorphic rocks that form by a process called metasomatism. 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 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 either 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 the original composition of both the hydrothermal fluid and the original composition of the protolith.

Chromite

Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of FeCr2O4. It is an oxide mineral belonging to the spinel group. The element magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite (MgCr2O4). A substitution of the element aluminium can also occur, leading to hercynite (FeAl2O4). Chromite today is mined particularly to make stainless steel through the production of ferrochrome (FeCr), which is an iron-chromium alloy.

Copper extraction

Copper extraction refers to the methods used to obtain copper from its ores. The conversion of copper consists of a series of physical and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors.

Adamite

Adamite is a zinc arsenate hydroxide mineral, Zn2AsO4OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds admixture. Tints of green also occur and are connected with copper substitutions in the mineral structure. Olivenite is a copper arsenate that is isostructural with adamite and there is considerable substitution between zinc and copper resulting in an intermediate called cuproadamite. Zincolivenite is a recently discovered mineral being an intermediate mineral with formula CuZn(AsO4)(OH). Manganese, cobalt, and nickel also substitute in the structure. An analogous zinc phosphate, tarbuttite, is known.

Bushveld Igneous Complex Large early layered igneous intrusion

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 2 billion years old and is divided into four different limbs: the northern, southern, eastern, and western limbs. The Bushveld Complex comprises the Rustenburg Layered suite, the Lebowa Granites and the Rooiberg Felsics, that are overlain by the Karoo sediments. The site was first discovered around 1897 by Gustaaf Molengraaff.

Great Dyke

The Great Dyke 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.

Ore genesis How the various types of mineral deposits form within the Earths crust

Various theories of ore genesis explain how the various types of mineral deposits form within the Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.

The Yilgarn Craton is a large craton that constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have been dated at ~4.27 Ga, with one detrital zircon dated as old as 4.4 Ga.

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.

In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary (hypogene) sulfide ore minerals and redistribute the metallic ore elements. Supergene enrichment occurs at the base of the oxidized portion of an ore deposit. Metals that have been leached from the oxidized ore are carried downward by percolating groundwater, and react with hypogene sulfides at the supergene-hypogene boundary. The reaction produces secondary sulfides with metal contents higher than those of the primary ore. This is particularly noted in copper ore deposits where the copper sulfide minerals chalcocite Cu2S, covellite CuS, digenite Cu18S10, and djurleite Cu31S16 are deposited by the descending surface waters.

Browns polymetallic ore deposit

The Browns polymetallic ore deposit is a large ore deposit located at Mount Fitch, near Batchelor, 64 kilometres south of Darwin, Northern Territory, Australia.

The mineral industry of Kazakhstan is one of the most competitive and fastest growing sectors of the country. Kazakhstan ranks second to Russia among the countries of the CIS in its quantity of mineral production. It is endowed with large reserves of a wide range of metallic ores, industrial minerals, and fuels, and its metallurgical sector is a major producer of a large number of metals from domestic and imported raw materials. In 2005, its metal mining sector produced bauxite, chromite, copper, iron, lead, manganese, and zinc ores, and its metallurgical sector produced such metals as beryllium, bismuth, cadmium, copper, ferroalloys, lead, magnesium, rhenium, steel, titanium, and zinc. The country produced significant amounts of other nonferrous and industrial mineral products, such as alumina, arsenic, barite, gold, molybdenum, phosphate rock, and tungsten. The country was a large producer of mineral fuels, including coal, natural gas, oil, and uranium. The country's economy is heavily dependent on the production of minerals. Output from Kazakhstan's mineral and natural resources sector for 2004 accounted for 74.1% of the value of industrial production, of which 43.1% came from the oil and gas condensate extraction. In 2004, the mineral extraction sector accounted for 32% of the GDP, employed 191,000 employees, and accounted for 33.1% of capital investment and 64.5% of direct foreign investment, of which 63.5% was in the oil sector. Kazakhstan's mining industry is estimated at US$29.5 billion by 2017.

Resources are classified as either biotic or abiotic on the basis of their origin. The Indian landmass contains a multitude of both types of pineapple and its economy, especially in rural areas, is heavily dependent on their consumption or export. Due to overconsumption, they are rapidly being depleted.

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.

Field (mineral deposit)

A field is a mineral deposit containing a metal or other valuable resources in a cost-competitive concentration. It is usually used in the context of a mineral deposit from which it is convenient to extract its metallic component. The deposits are exploited by mining in the case of solid mineral deposits and extraction wells in case of fluids.

References

  1. 1 2 Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April 2021
  2. 1 2 Neuendorf, K.K.E., Mehl, J.P., Jr., and Jackson, J.A., eds., 2011, Glossary of Geology: American Geological Institute, 799 p.
  3. 1 2 Hustrulid, William A.; Kuchta, Mark; Martin, Randall K. (2013). Open Pit Mine Planning and Design. Boca Raton, Florida: CRC Press. p. 1. ISBN   9781482221176 . Retrieved 5 May 2020.
  4. Arndt, N. and others (2017) Future mineral resources, Chap. 2, Formation of mineral resources, Geochemical Perspectives, v6-1, p. 18-51.
  5. 1 2 Leach, D. and others (2010) Sediment-hosted lead-zinc deposits in Earth history. Economic Geology, v. 105, p. 593-625.
  6. Sillitoe, R.H., Perello, J., Creaser, R.A., Wilton, J., Wilson, A.J., and Dawborn, T., 2017, Reply to discussions of “Age of the Zambian Copperbelt” by Hitzman and Broughton and Muchez et al.:, p. 1–5, doi: 10.1007/s00126-017-0769-x.
  7. "Background Paper - The Outlook for Metals Markets Prepared for G20 Deputies Meeting Sydney 2006" (PDF). The China Growth Story. WorldBank.org. Washington. September 2006. p. 4. Retrieved 2019-07-19.

Further reading

Commons-logo.svg Media related to Ores at Wikimedia Commons