Tungsten (ˈtʌŋstən/), also known as wolfram (play /ˈwʊlfrəm/ WOOL-frəm), is a chemical element with the chemical symbol W and atomic number 74. (more…)
Molybdenum is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores. (more…)
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Uranium mining is the process of extraction of uranium ore from the ground. As uranium ore is mostly present at relatively low concentrations, most uranium mining is very volume-intensive, and thus tends to be undertaken as open-pit mining. It is also undertaken in only a small number of countries of the world, as the resource is rare.
The worldwide production of uranium in 2008 amounted to 43,853 tonnes, of which 20% was mined in Canada. Canada, Kazakhstan, and Australia are the top three producers and together account for 59% of world uranium production. Other important uranium producing countries in excess of 1000 tonnes per year are Namibia, Russia, Niger, Uzbekistan, and the United States.
A prominent use of uranium from mining is as fuel for nuclear power plants. As of 2008, known uranium ore resources which can be mined at about current costs are estimated to be sufficient to produce fuel for about a century, based on current consumption rates.
After mining uranium ores, they are normally processed by grinding the ore materials to a uniform particle size and then treating the ore to extract the uranium by chemical leaching. The milling process commonly yields dry powder-form material consisting of natural uranium, “yellowcake,” which is sold on the uranium market as U3O8.
Uranium minerals were noticed by miners for a long time prior to the discovery of uranium in 1789. The uranium mineral pitchblende, also known as uraninite, was reported from the Erzgebirge Ore Mountains, Saxony, as early as 1565. Other early reports of pitchblende date from 1727 in Joachimsthal and 1763 in Schwarzwald.
In the early 1800s, uranium ore was recovered as a by-product of mining in Saxony, Bohemia, and Cornwall. The first deliberate mining of radioactive ores took place in Jáchymov, also known by its German name Joachimsthal, a silver-mining city in what is now the Czech Republic. Marie Curie used pitchblende ore from Jáchymov to isolate the element radium, a decay product of uranium; her death was from aplastic anemia, almost certainly due to exposure to radioactivity. Until World War II uranium mining was done primarily for the radium content. Sources for radium, contained in the uranium ore, were sought for use as luminous paint for watch dials and other instruments, as well as for health-related applications, some of which in retrospect were incredibly unhealthy. The byproduct uranium was used mostly as a yellow pigment.
In the United States, the first radium/uranium ore was discovered in 1871 in gold mines near Central City, Colorado. This district produced about 50 tons of high grade ore between 1871 and 1895. However, most American uranium ore before World War II came from vanadium deposits on the Colorado Plateau of Utah and Colorado.
In Cornwall, the South Terras Mine near St. Stephen opened for uranium production in 1873, and produced about 175 tons of ore before 1900. Other early uranium mining occurred in Autunois in France’s Massif Central, Oberpfalz in Bavaria, and Billingen in Sweden.
The Shinkolobwe deposit in Katanga, Belgian Congo now Shaba Province, Zaire was discovered in 1913, and exploited by the Union Minière du Haut Katanga. Other important early deposits include Port Radium, near Great Bear Lake, Canada discovered in 1931, along with Beira Province, Portugal; Tyuya Muyun, Uzbekistan, and Radium Hill, Australia.
Because of the need for the uranium for bomb research during World War II, the Manhattan Project used a variety of sources for the element. The Manhattan Project initially purchased uranium ore from the Belgian Congo, through the Union Minière du Haut Katanga. Later the project contracted with vanadium mining companies in the American Southwest. Purchases were also made from the Eldorado Mining and Refining Limited company in Canada. This company had large stocks of uranium as waste from its radium refining activities.
American uranium ores mined in Colorado were mixed ores of vanadium and uranium, but because of wartime secrecy the Manhattan Project would only publicly admit to purchasing the vanadium, and did not pay the uranium miners for the uranium content. In a much later lawsuit, many miners were able to reclaim lost profits from the U.S. government. American ores had much lower uranium concentrations than the ore from the Belgian Congo, but they were pursued vigorously to ensure nuclear self-sufficiency.
Similar efforts were undertaken in the Soviet Union, which did not have native stocks of uranium when it started developing its own atomic weapons program.
Intensive exploration for uranium started after the end of World War II as a result of the military and civilian demand for uranium. There were three separate periods of uranium exploration or “booms.” These were from 1956 to 1960, 1967 to 1971, and from 1976 to 1982
In the 20th century the United States was the world’s largest uranium producer. Grants Uranium District in northwestern New Mexico was the largest United States uranium producer. The Gas Hills Uranium District, was the second largest uranium producer. The famous Lucky Mc Mine is located in the Gas Hills near Riverton, Wyoming. Canada has since surpassed the United States as the cumulative largest producer in the world.
2007 uranium mining, by nationality.
Production in Australia rose significantly to 10,115 tU3O8 (22.3 million pounds) in 2007 from 19.7 million pounds in 2006, securing its position as the second largest uranium producing country, most of the production gain coming from increased operational performance and an increase in the grade of the ore mined.
Australia has the world’s largest uranium reserves – 24 percent of the planet’s known reserves. The majority of these reserves are located in South Australia with other important deposits in Queensland, Western Australia and the Northern Territory. Almost all the uranium is exported under strict International Atomic Energy Agency safeguards to satisfy the Australian people and government that none of the uranium is used in nuclear weapons. Australian uranium is used strictly for electricity production.
The Olympic Dam operation run by BHP Billiton in South Australia is combined with mining of copper, gold, and silver, and has reserves of global significance. There are currently three operating uranium mines in Australia, and several more have been proposed. The expansion of Australia’s uranium mines is supported by the Federal Australian Labor Party (ALP) Government headed by Prime Minister Kevin Rudd. The ALP abandoned its long-standing and controversial “no new uranium mines” policy in April 2007. One of the more controversial proposals was Jabiluka, to be built surrounded by the World Heritage listed Kakadu National Park. The existing Ranger Uranium Mine is also surrounded by the National Park as the mine area was not included in the original listing of the Park.
Uranium mining and export and related nuclear issues have often been the subject of public debate, and the anti-nuclear movement in Australia has a long history.
Canada is the largest exporter of uranium ore, with the largest mines located in Athabasca Basin in northern Saskatchewan.
Canada’s first uranium discovery was in the Alona Bay area, south of Lake Superior Provincial Park in Ontario, by Dr. John Le Conte in 1847. But the Canadian uranium industry really began with the 1932 discovery of pitchblende at Port Radium, Northwest Territories. The deposit was mined from 1933 to 1940, for radium, silver, copper, and cobalt. The mine shut down in 1940, but was reopened in 1942 by Eldorado Mining and Refining Limited to supply uranium to the Manhattan Project. The Canadian government expropriated the Port Radium mine and banned private claimstaking and mining of radioactive minerals.
In 1947 the government lifted the ban on private uranium mining, and the industry boomed through the 1950s, spurred by high prices due to the nuclear weapons programs. Production peaked in 1959, when 23 mines in five different districts made uranium Canada’s number-one export. That same year, however, Great Britain and the United States announced their intention to halt uranium purchases in 1963. By 1963, seven mines were left operating, a number that shrank to only three in 1972.
A price rise caused uranium to boom again in 1975 and 2005.
Despite overall country production falling some 4% to 11,158 t (24.6 million pounds) U3O8, Canada is again the world’s largest uranium producing country, accounting for 23% of world production in 2007. Production was led by Cameco’s majority-owned McArthur River/Key Lake JV which yielded a total of 8,482 t (18.7 million pounds) U3O8 in 2007, which was the same level as in 2006. Cameco’s 100%-owned Rabbit Lake mine produced 1,814 t (4.0 million pounds) U3O8, which was a 21.7% decline from production of 5.1 million pounds (2,300 t) in 2006.
In 1948, prospector Robert Campbell discovered pitchblende at Theano Point, in the area of Alona Bay, Ontario, and staked 30 claims. By November 1948 a rush had begun, and in the next three years, 5,000 claims would be staked in the area. A shaft and headframe were constructed, but abandoned before operations could begin; the mine proved unprofitable after uranium discoveries at Elliot Lake, Ontario.
The uranium-bearing pegmatite of Bancroft, Ontario began mining in 1952.
Uranium was discovered at Blind River-Elliot Lake area in 1949, and production began in 1955. The deposits are in Precambrian quartz-pebble conglomerates, similar to uranium deposits in Brazil and South Africa.
The headframe of the Gunnar mine, in Saskatchewan
Pitchblende veins were discovered near Beaverlodge Lake, Saskatchewan in 1935, and uranium mining started in 1953.
Today the Athabasca Basin in northern Saskatchewan hosts the largest high-grade uranium mines and deposits. Cameco, the world’s largest low-cost uranium producer, which accounts for 18% of the world’s uranium production, operates three mines and one dedicated mill in the region. Among the major mines are Cameco’s flagship McArthur River mine, the developing Cigar Lake mine, the Rabbit Lake mine and mill complex, and the world’s largest uranium mill at Key Lake. French-owned uranium syndicate Areva also operates the McClean Lake mill. Most of these mines are joint ventures between Cameco, Areva, and various other joint venture shareholders. Future mines currently in early development stages include Areva’s Midwest Project (near McClean Lake), and Cameco’s Millennium Project (near Key Lake). As of 2007, with uranium spot market prices well over the $100 USD/lb mark, Saskatchewan has become a hotbed of uranium exploration, with many junior exploration companies rushing to explore the highly valuable Athabasca basin.
Most uranium ore in the United States comes from deposits in sandstone, which tend to be of lower grade than those of Australia and Canada. Because of the lower grade, many uranium deposits in the United States became uneconomic when the price of uranium declined sharply in the 1980s.
Regular production of uranium-bearing ore in the United States began in 1898 with the mining of carnotite-bearing sandstones of the Colorado Plateau in Colorado and Utah, for their vanadium content. The discovery of radium by Marie Curie, also in 1898, soon made the ore also valuable for radium. Uranium was a by-product. By 1913, the Colorado Plateau uranium-vanadium province was supplying about half the world supply of radium. Production declined sharply after 1923, when low-cost competition from radium from the Belgian Congo and vanadium from Peru made the Colorado Plateau ores uneconomic.
Mining revived in the 1930s with higher prices for vanadium. American uranium ores were in very high demand by the Manhattan Project during World War II, although the mining companies did not know that the by-product uranium was suddenly valuable. The late 1940s and early 1950s saw a boom in uranium mining in the western US, spurred by the fortunes made by prospectors such as Charlie Steen.
Uranium mining declined with the last open pit mine (Shirley Basin, Wyoming) shutting down in 1992. United States production occurred in the following states (in descending order): New Mexico, Wyoming, Colorado, Utah, Texas, Arizona, Florida, Washington, and South Dakota. The collapse of uranium prices caused all conventional mining to cease by 1992. In-situ leach mining has continued primarily in Wyoming and adjacent Nebraska as well has recently restarted in Texas. Rising uranium prices since 2003 have increased interest in uranium mining in the United States.
On Wednesday 25 June 2008 the House Natural Resources Committee voted overwhelmingly to enact emergency protections from uranium mining for 1,000,000 acres (4,000 km2) of public lands around Grand Canyon National Park. This will mean the Secretary of the Interior has an obligation to protect public lands near the Grand Canyon from uranium extraction for three years. The Center for Biological Diversity, Sierra Club, and the Grand Canyon Trust recently won a court order against the Kaibab National Forest stopping uranium drilling near the national park until a thorough environmental analysis is conducted.
The Grand Canyon Watersheds Protection Act has been proposed. This is a bill that would permanently ban uranium mining in the area. The impacts of uranium development have raised concerns of scientists and government officials alike. Due to increasing demand, uranium projects have been on the increase posing a threat to water, public health, and fragile desert ecosystems.
Kazakhstan produced some 7847 tU3O8 (17.3 million pounds in 2007), much more than in 2006. Kazatomprom’s four 100%-owned ISR mining groups (LLP Kazatomprom) combined produced half of the total output.
The World Nuclear Association states that Russia has known uranium deposits of 500,000 tonnes and plans to mine 11,000 to 12,000 tonnes per year from deposits in the South Urals, Western Siberia, and Siberia east of Lake Baikal, by 2010.
The Russian nuclear industry has been undergoing an overall restructuring process during 2007. The production was high as almost 4 000 tU3O8 (8.8 million pounds) from three operating mines in 2007. Atomredmetzoloto reported that the Priargunsky mine yielded 7.8 million pounds in 2007, a slight decline from the 8.2 million pounds reported by TVEL in 2006. At the Dalur (Dolmatovskoye) and Khiagda ISR mines, production of 910 000 pounds and 68 000 pounds, respectively, was reached in 2007. Both ISR projects are expected to increase production steadily through 2015.
Ukraine’s VostGOK produced almost 1000 tU3O8 (2.2 million pounds) from the Zhovti Vody mill in 2007, which was similar to the 2.1 million pounds produced in 2006.
In Uzbekistan, the Navoi Mining & Metallurgy Combinat reportedly produced 2,721 tonnes U3O8 or tU3O8 (6 million pounds) from its Nurabad, Uchkuduk and Zafarabad in-situ recovery facilities.
Sources of uranium delivered to EU utilities in 2007, from the 2007 Annual report of the Euratom Supply Agency
European uranium mining supplied just below 3% of the total EU needs, coming from the Czech Republic and Romania (a total of 526 tU). Production in the Rožňa mine was to be terminated in 2008, but the Czech Government decided in May 2007 to continue mining and extended the lifetime without time limit as long as it remains profitable.
Bulgaria shut down its facilities for environmental reasons in 1992; terrains were recultivated but recently, there has been certain interest in resuming activities. Industrial mining first started in 1938 and was resumed after 1944 by a joint Soviet-Bulgarian mining company, reorganized in 1956 into the Redki Metali (Rare Metals) government-owned concern. At its peak, it had 13,000 employees, operated 48 uranium mines and two enrichment plants at Buhovo outside Sofia and Eleshnitsa near Bansko. Yearly production was estimated at 645 t that met about 55% of the needs of Kozloduy Nuclear Power Plant, which had six reactors with a total output of over 3600 MWe at its peak.
The Czech Republic is the birthplace of industrial scale uranium mining. Uranium mining at Jáchymov (at that time named Joachimsthal and belonging to Austria-Hungary) started in the 1890s on an industrial scale, after the silver and cobalt production of the deposit went down. Uranium was first used to produce mainly yellow colours for glass and porcelain manufacture. After the Curies in France discovered the Polonium and Radium in tailings from Jáchymov, the town became the first place in the world for commercial radium production from uranium ore. Radioactive water from the mines was also used to set up a health resort still exisiting today for radon-treatments. Pre-Cold War production is estimated to be around 1,000 t of uranium. From 1947 on the Czech Republic started producing uranium for the Soviet Union. Early mining sites like Jáchymov, Horní Slavkov and Příbram became infamously known as parts of the “Czech Gulag”. In the whole, the Czech Republic produced 110.000 t of uranium to 1992 from 64 uranium deposits. The largest deposit Příbram (vein style) produced about 50.000 t of uranium and was mined to a depth of over 1,800 m.
Today, the Rožná underground facility 55 km northwest of Brno is Europe’s only operating uranium mine, continuously operating since 1957. It produces about 300 t of uranium annualy. Since 2007, the Australian company Uran Ltd. is interested to participate in the operations at Rožná, as well as seeking permits with the Czech Ministry of Trade and Resources to open mines in the Czech Republic at other known locations, like Brzkov, Jamné, Polná and Věžnice, through its Czech partner Timex Zdice and since 2008 through its subsidiary Urania Mining.
During 1946–1952, the Dictyonema argillite (claystone) was mined and used for uranium production in Sillamäe.
In Uusimaa, Karelia and Lapland in Finland, presently (2009) uranium deposits are investigated
Search for uranium ore intensified during the cold war, but only in East Germany was an extensive uranium mining industry established. Uranium was mined from 1947 to 1990 from mines in Saxony and Thuringia by the SDAG Wismut. All the uranium mines were closed after the German reunification for economic and environmental reasons. Total production in East Germany was 230.400 t of uranium making it the third largest producer in history behind the USA and Canada. A minor production still takes place at the Königstein mine southeast of Dresden from cleaning of mine water. This production has been 38 t of uranium in 2007.
In Hungary uranium mining began in the 1950s around Pécs to supply the country’s first atomic plant in Paks. A whole district was built for the mining industry on the outskirt of Pécs, for which the name Uránváros (Uranium city) was given. After the fall of communism, uranium mining was gradually given up because of the high production costs. That caused serious economic problems and a rise of unemployment in Pécs. Recently an Australian company took up the challenge to search for uranium in the Mecsek.
Romania produced in 2008 around 250 tonnes of uranium.
A mine is proposed for near the towns of Jahodná and Košice
In Sweden, uranium production took place at Ranstadsverket between 1965 and 1969 by mining of alum shale (kind of oil shale) deposits. The goal was to make Sweden self-supplying with uranium. The high operating costs of the pilot plant (heap leaching) due to the low concentration of uranium in the shale and the, at that time, availability of comparatively cheap uranium on the world market, caused the mine to be closed, although a much cheaper and more efficient leaching process, using sulfur-consuming bacteria, had by then been developed. Since 2005 there have been investigations on opening new uranium mines in Sweden.
The South Terras Mine in Cornwall was mined for uranium from 1873 to 1903.
Substantial uranium deposits were found on Orkney in the 1970s, When Margaret Thatcher proposed a uranium mine on Orkney a campaign followed which successfully argued that uranium mining would mean irreversible environmental, social and psychological damage.
Namibia produces uranium at Rossing deposit, where an igneous deposit is mined from one of the world’s largest open pit mines. The mine is owned by a subsidiary of the Rio Tinto Group. The Langer Heinrich calcrete uranium deposit was discovered in 1973 and the open pit mine was officially opened in 2007.
Niger is Africa’s leading uranium-producing nation. Uranium is produced from mines at Arlit owned by Areva NC.
In 2007, production in Niger had a total output of 3720 tonnes U3O8 (8.2 million pounds) coming mainly from the Akouta (Cominak) and the Arlit (Somair) mines.
Niger’s uranium came to world attention before the US invasion of Iraq, when it was asserted that Iraq had attempted to buy uranium from Niger
South Africa produces uranium from deposits in Precambrian quartz-pebble conglomerates of the Witwatersrand Basin, at Brakpan and Krugersdorp, Gauteng.
China mined in 2007 636 tonnes of U3O8, a decrease of 17% of its production in 2006
In Nalgonda District, the Rajiv Gandhi Tiger Reserve (the only tiger project in Andhra Pradesh) has been forced to surrender over 1,000 sq. kilometres to uranium mining following a directive from the Central Ministry of Environment and Forests.
In 2007, India was able to extract 229 tonnes of U3O8 from its soil
Jordan, the only Middle East country with confirmed uranium, is estimated to have around 140,000 tonnes in its uranium reserves plus a further 59,000 tonnes in phosphate deposits. Although no uranium has been mined yet, it was announced in 2008 that the Jordanian Government signed an agreement with the French Company AREVA to explore for uranium. This will benefit them on building a future nuclear plant in Jordan.
Uranium prospecting is similar to other forms of mineral exploration with the exception of some specialized instruments for detecting the presence of radioactive isotopes.
The Geiger counter was the original radiation detector, recording the total count rate from all energy levels of radiation. Ionization chambers and Geiger counters were first adapted for field use in the 1930s. The first transportable Geiger–Müller counter (weighing 25 kg) was constructed at the University of British Columbia in 1932. H.V. Ellsworth of the GSC built a lighter weight, more practical unit in 1934. Subsequent models were the principal instruments used for uranium prospecting for many years, until geiger counters were replaced by scintillation counters.
The use of airborne detectors to prospect for radioactive minerals was first proposed by G.C. Ridland, a geophysicist working at Port Radium in 1943. In 1947, the earliest recorded trial of airborne radiation detectors (ionization chambers and Geiger counters) was conducted by Eldorado Mining and Refining Limited. (a Canadian Crown Corporation since sold to become Cameco Corporation). The first patent for a portable gamma-ray spectrometer was filed by Professors Pringle, Roulston & Brownell of the University of Manitoba in 1949, the same year as they tested the first portable scintillation counter on the ground and in the air in northern Saskatchewan.
Airborne gamma-ray spectrometry is now the accepted leading technique for uranium prospecting with worldwide applications for geological mapping, mineral exploration & environmental monitoring.
A deposit of uranium, discovered by geophysical techniques, is evaluated and sampled to determine the amounts of uranium materials that are extractable at specified costs from the deposit. Uranium reserves are the amounts of ore that are estimated to be recoverable at stated costs.
Types of uranium deposits
Many different types of uranium deposits have been discovered and mined.
Uranium deposits in sedimentary rock
A Uranium mine, near Moab, Utah. Note alternating red and white/green sandstone. This corresponds to oxidized and reduced conditions in groundwater redox chemistry. The rock forms in oxidizing conditions, and is then “bleached” to the white/green state when a reducing fluid passes through the rock. The reduced fluid can also carry Uranium-bearing minerals.
Uranium deposits in sedimentary rocks include those in sandstone (in Canada and the western US), Precambrian unconformities (in Canada),phosphate, Precambrian quartz-pebble conglomerate, collapse breccia pipes (see Arizona Breccia Pipe Uranium Mineralization), and calcrete.
Sandstone uranium deposits are generally of two types. Roll-front type deposits occur at the boundary between the up dip and oxidized part of a sandstone body and the deeper down dip reduced part of a sandstone body. Peneconcordant sandstone uranium deposits, also called Colorado Plateau-type deposits, most often occur within generally oxidized sandstone bodies, often in localized reduced zones, such as in association with carbonized wood in the sandstone.
Precambrian quartz-pebble conglomerate-type uranium deposits occur only in rocks older than two billion years old. The conglomerates also contain pyrite. These deposits have been mined in the Blind River-Elliot Lake district of Ontario, Canada, and from the gold-bearing Witwatersrand conglomerates of South Africa.
Igneous or hydrothermal uranium deposits
Hydrothermal uranium deposits encompass the vein-type uranium ores. Igneous deposits include nepheline syenite intrusives at Ilimaussaq, Greenland; the disseminated uranium deposit at Rossing, Namibia; and uranium-bearing pegmatites. Disseminated deposits are also found in the states of Washington and Alaska in the US.
As with other types of hard rock mining there are several methods of extraction. The main methods of mining are box cut mining, open pit mining and in situ leaching (ISL).
In open pit mining, overburden is removed by drilling and blasting to expose the ore body, which is then mined by blasting and excavation using loaders and dump trucks. Workers spend much time in enclosed cabins thus limiting exposure to radiation. Water is extensively used to suppress airborne dust levels.
Underground uranium mining
If the uranium is too far below the surface for open pit mining, an underground mine might be used with tunnels and shafts dug to access and remove uranium ore. There is less waste material removed from underground mines than open pit mines, however this type of mining exposes underground workers to the highest levels of radon gas.
Underground uranium mining is in principle no different to any other hard rock mining and other ores are often mined in association (eg copper, gold, silver). Once the ore body has been identified a shaft is sunk in the vicinity of the ore veins, and crosscuts are driven horizontally to the veins at various levels, usually every 100 to 150 metres. Similar tunnels, known as drifts, are driven along the ore veins from the crosscut. To extract the ore, the next step is to drive tunnels, known as raises when driven upwards and winzes when driven downwards through the deposit from level to level. Raises are subsequently used to develop the stopes where the ore is mined from the veins.
The stope, which is the workshop of the mine, is the excavation from which the ore is extracted. Two methods of stope mining are commonly used. In the “cut and fill” or open stoping method, the space remaining following removal of ore after blasting is filled with waste rock and cement. In the “shrinkage” method, only sufficient broken ore is removed via the chutes below to allow miners working from the top of the pile to drill and blast the next layer to be broken off, eventually leaving a large hole. Another method, known as room and pillar, is used for thinner, flatter ore bodies. In this method the ore body is first divided into blocks by intersecting drives, removing ore while so doing, and then systematically removing the blocks, leaving enough ore for roof support.
Waste rock is produced during open pit mining when overburden is removed, and during underground mining when driving tunnels through non-ore zones.
Piles of these tailings often contain elevated concentrations of radioisotopes compared to normal rock. Other waste piles consist of ore with too low a grade for processing. The difference between waste rock and ore depends on technical and economic feasibility criteria, principally market price for ore. All these piles threaten people and the environment after shut down of the mine due to their release of radon gas and seepage water containing radioactive and toxic materials.
In some cases uranium has been removed from this low-grade ore by heap leaching. This may be done if uranium content is too low for the ore to be economically processed in a uranium mill. The leaching liquid (often sulfuric acid) is introduced on the top of the pile and percolates down until it reaches a liner below the pile, where it is caught and pumped to a processing plant. Due to the potential for extreme damage to the surrounding environment, this practice is no longer in use.
Heap leaching using carbonate is seen as an environmentally responsible way to extract uranium because the only leaching reagent is sodium bicarbonate (baking soda) and is currently being tested for use at Ranger uranium in the Northern Territory of Australia, at Trekkopje in Namibia, at Wiluna in Western Australia, and at Letlhakane in Botswana.
In-situ leaching (ISL), sometimes referred to as in-situ recovery (ISR) or solution mining, is performed by pumping liquids (weak acid or weak alkaline depending on the calcium concentration in the ore) down through injection wells placed on one side of the deposit of uranium, through the deposit, and up through recovery wells on the opposing side of the deposit – recovering ore by leaching. ISL is also used on other types of metal extraction such as copper. ISL is often cost-effective because it avoids excavation costs, and may be implemented more quickly than conventional mining. However, it is not suitable to all uranium deposits, as the host rock must be permeable to the liquids (as is often the case in sandstone), making it possible to contaminate nearby aquifers with leaching chemicals. Evironmental impact studies are performed when evaluating ISL, because ground water can be affected. In-situ leaching is the only type of uranium mining currently being done in the United States (2006).
Recovery from seawater
The uranium concentration of sea water is low, approximately 3.3 mg per cubic meter of seawater (3.3 ppb). But the quantity of this resource is gigantic and some scientists believe this resource is practically limitless with respect to world-wide demand. That is to say, if even a portion of the uranium in seawater could be used the entire world’s nuclear power generation fuel could be provided over a long time period. Some anti-nuclear proponents claim this statistic is exaggerated. Although research and development for recovery of this low-concentration element by inorganic adsorbents such as titanium oxide compounds, has occurred since the 1960s in the United Kingdom, France, Germany, and Japan, this research was halted due to low recovery efficiency.
At the Takasaki Radiation Chemistry Research Establishment of the Japan Atomic Energy Research Institute (JAERI Takasaki Research Establishment), research and development has continued culminating in the production of adsorbent by irradiation of polymer fiber. Adsorbents have been synthesized that have a functional group (amidoxime group) that selectively adsorbs heavy metals, and the performance of such adsorbents has been improved. Uranium adsorption capacity of the polymer fiber adsorbent is high, approximately tenfold greater in comparison to the conventional titanium oxide adsorbent.
One method of extracting uranium from seawater is using a uranium-specific nonwoven fabric as an absorbent. The total amount of uranium recovered from three collection boxes containing 350 kg of fabric was >1 kg of yellowcake after 240 days of submersion in the ocean. According to the OECD, uranium may be extracted from seawater using this method for about $300/kg-U. The experiment by Seko et al. was repeated by Tamada et al. in 2006. They found that the cost varied from ¥15,000 to ¥88,000 (Yen) depending on assumptions and “The lowest cost attainable now is ¥25,000 with 4g-U/kg-adsorbent used in the sea area of Okinawa, with 18 repetitionuses [sic].” With the May, 2008 exchange rate, this was about $240/kg-U.
Rise, stagnation, renaissance and opposition to uranium mining
In the beginning of the Cold War, to ensure adequate supplies of uranium for national defense, the United States Congress passed the U.S. Atomic Energy Act of 1946, creating the Atomic Energy Commission (AEC) which had the power to withdraw prospective uranium mining land from public purchase, and also to manipulate the price of uranium to meet national needs. By setting a high price for uranium ore, the AEC created a uranium “boom” in the early 1950s, which attracted many prospectors to the four corners region of the country. Moab, Utah became known as the Uranium-capital of the world, when geologist Charles Steen discovered such an ore in 1952, even though American ore sources were considerably less potent than those in the Belgian Congo or South Africa.
At the height of the nuclear energy euphoria in the 1950s methods for extracting diluted uranium and thorium, found in abundance in granite or seawater, were pursued. Scientists promised that, used in a breeder reactor, these materials would potentially provide limitless source of energy.
American military requirements declined in the 1960s, and the government completed its uranium procurement program by the end of 1970. Simultaneously, a new market emerged: commercial nuclear power plants. However, in the U.S. this market virtually collapsed by the end of the 1970s as a result of industrial strains caused by the energy crisis, popular opposition, and finally the Three Mile Island nuclear accident in 1979, all of which led to a de facto moratorium on the development of new nuclear reactor power stations.
In Europe a mixed situation exists. Considerable nuclear power capacities have been developed, notably in Belgium, France, Germany, Spain, Sweden, Switzerland and the UK. In many countries development of nuclear power has been stopped and phased out by legal actions. In Italy the use of nuclear power was barred by a referendum in 1987, however this is now under revision. Ireland also has no plans to change its non-nuclear stance and pursue nuclear power in the future.
Opposition to uranium mining has been considerable in Australia, where notable anti-uranium activists have included Kevin Buzzacott, Jacqui Katona, Yvonne Margarula, and Jillian Marsh. Other notable anti-uranium activists include Manuel Pinto (USA), JoAnn Tall (USA), and Sun Xiaodi (China).
Since 1981 uranium prices and quantities in the US are reported by the Department of Energy. The import price dropped from 32.90 US$/lb-U3O8 in 1981 down to 12.55 in 1990 and to below 10 US$/lb-U3O8 in the year 2000. Prices paid for uranium during the 1970s were higher, 43 US$/lb-U3O8 is reported as the selling price for Australian uranium in 1978 by the Nuclear Information Centre.
Uranium prices reached an all-time low in 2001, costing US$7/lb, but has since rebounded strongly. In April 2007 the price of Uranium on the spot market rose to US$113.00/lb, This is very close to the all time high (adjusted for inflation) in 1977. a high point of the uranium bubble of 2007. The higher price has spurred expansion of current mines, construction of new mines and reopening of old mines as well as new prospecting.
Health risks of uranium mining
Because uranium ore emits radon gas, uranium mining can be more dangerous than other underground mining, unless adequate ventilation systems are installed. During the 1950s, many Navajos in the U.S. became uranium miners, as many uranium deposits were discovered on Navajo reservations. A statistically significant subset of these early miners later developed small cell carcinoma after exposure to uranium ore. Radon-222, a natural decay product of uranium, has been shown to be the cancer-causing agent. Some American survivors and their descendants received compensation under the Radiation Exposure Compensation Act in 1990.
In January 2008 Areva was nominated for an Anti Oscar Award. The French state-owned company mines uranium in northern Niger where mine workers are not informed about health risks, and analysis shows radioactive contamination of air, water and soil. The local organization that represents the mine workers, spoke of “suspicious deaths among the workers, caused by radioactive dust and contaminated groundwater.”
Despite efforts made in cleaning up uranium sites, significant problems stemming from the legacy of uranium development still exist today on the Navajo Nation and in the states of Utah, Colorado, New Mexico, and Arizona. Hundreds of abandoned mines have not been cleaned up and present environmental and health risks in many communities. At the request of the U.S. House Committee on Oversight and Government Reform in October 2007, and in consultation with the Navajo Nation, the Environmental Protection Agency (EPA), along with the Bureau of Indian Affairs (BIA), the Nuclear Regulatory Commission (NRC), the Department of Energy (DOE), and the Indian Health Service (IHS), developed a coordinated Five-Year Plan to address uranium contamination. Similar interagency coordination efforts are beginning in the State of New Mexico as well.
Hubbert’s Peak and Uranium
The peak uranium concept follows from M. King Hubbert’s peak theory, most commonly associated with Peak oil. Hubbert saw oil as a resource which would soon run out, and believed uranium had much more promise as an energy source. Hubbert believed that breeder reactors and nuclear reprocessing, which were new technologies at the time, would allow uranium to be a power source for a very long time. The technologies Hubbert envisioned are not economically feasible or widely deployed to date. As a result, the vast majority of uranium is now used in a “once-through” cycle. As for any finite resource, the Hubbert peak theory still applies.
According to the Hubbert Peak Theory, Hubbert’s peaks are the points where production of a resource, has reached its maximum, and from then on, the rate of resource production enters a terminal decline. After a Hubbert’s peak, the rate of supply of a resource no longer fulfills the previous demand rate. As a result of the law of supply and demand, at this point the market shifts from a buyer’s market to a seller’s market.
Many countries have hit peak uranium and are not able to supply their own uranium demands any longer and have to import uranium from other countries or abandon nuclear power. Thirteen countries have hit peak and exhausted their uranium resources.
World consumption of primary energy by energy type in terawatts (TW), 1965-2005.
(Green-Oil; Black-Coal; Red-Gas; Purple- Nuclear; Blue-Hydro)
The world demand for uranium in 1996 was over 68 kilotonnes (150×10^6 lb) per year, and that number is expected to increase to 80 kilotonnes (180×10^6 lb) to 100 kilotonnes (220×10^6 lb) per year by 2025 due to the number of new nuclear power plants coming on line.
According to Cameco Corporation, the demand for uranium is directly linked to the amount of electricity generated by nuclear power plants. Reactor capacity is growing slowly, reactors are being run more productively, with higher capacity factors, and reactor power levels. Improved reactor performance translates into greater uranium consumption.
Nuclear power stations of 1000 megawatt electrical generation capacity (1000 MWe or 1 gigawatt electrical = 1GWe) require around 200 tonnes (440×10^3 lb) of uranium per year. For example, the United States has 103 operating reactors with an average generation capacity of 950 MWe demanded over 22 kilotonnes (49×10^6 lb) of uranium in 2005. As population and industrialization increases, more nuclear power plants will be built. As the number of nuclear power plants increase, so does the demand for uranium.
Note the vertical axis is logarithmic & is millions of people.
Another factor to consider is population growth. Electricity consumption is determined in part by economic and population growth. According to data from the CIA’s 2007 World Factbook, the world human population currently is more than 6.6 Billion (July 2007 est.) and it is increasing by 1.167% per year. This means a growth of about 211,000 persons every day.According to the UN, by 2050 it is estimated that the Earth’s human population will be 9.07 billion. That’s 37% increase from today. 62% of the people will live in Africa, Southern Asia and Eastern Asia.The largest energy-consuming class in the history of earth is being produced in world’s most populated countries, China and India. Both plan massive nuclear energy expansion programs. China intends to build 32 nuclear plants with 40,000 MWe capacity by 2020. By 2050, will deploy 300 or more additional plants. India plans on bringing 20,000 MWe nuclear capacity on line by 2020. By 2050, India will supply 25% of electricity from nuclear power. This is being repeated in dozens of lesser developed countries to meet the needs of their burgeoning middle classes.
As countries get more industrialized and their economy grows, so does the demand for electricity. Nearly 2 billion people across the planet have no electricity. The World Nuclear Association (WNA) believes nuclear energy could reduce the fossil fuel burden of generating the new demand for electricity. The WNA forecasts a 40-percent jump in worldwide electricity demand over the next five years. As countries get more industrialized, the higher their Human Development Index (HDI). The higher the HDI, the higher the electric consumption.
As more fossil fuels are used to supply the growing energy needs of an increasing population, the more greenhouse gases are produced. Some proponents of nuclear power believe that building more nuclear power plants can reduce greenhouse emissions. For example, the Swedish utility Vattenfall studied the full life cycle emissions of different ways to produce electricity, and concluded that nuclear power produced 3.3 g/kWh of carbon dioxide, compared to 400.0 for natural gas and 700.0 for coal. However, more recent studies have shown amounts in the range of 60 to 65g/kWh.
As world oil is expected to peak early this century, alternatives for gasoline and diesel for powering transportation are being sought. One of the promising solutions are hybrid and electric vehicles. Some experts believe that these vehicles will require 160 new power plants. Others believe none. The true figure lies somewhere between.
As countries are not able to supply their own needs economically from their own mines have resorted to importing better grades of uranium from elsewhere. For example, owners of U.S. nuclear power reactors bought 67 million pounds (30 kt) of uranium in 2006. Out of that 84%, or 56 million pounds (25 kt), were imported from foreign suppliers, according to the Energy Department.
Uranium occurs naturally in many rocks, and even in seawater. However, like other metals, it is seldom sufficiently concentrated to be economically recoverable. Like any resource, uranium cannot be mined at any desired concentration. No matter the technology, at some point it is too costly to mine lower grade ores. One life cycle study argues that below 0.01–0.02% (100-200 ppm) in ore, the energy required to extract and process the ore to supply the fuel, operate reactors and dispose properly comes close to the energy gained by burning the uranium in the reactor. Mining companies consider concentrations greater than 0.075% (750 ppm) as ore, or rock economical to mine.
|Very high-grade ore – 20% U||200,000 ppm U|
|High-grade ore – 2% U||20,000 ppm U|
|Low-grade ore – 0.1% U||1,000 ppm U|
|Very low-grade ore – 0.01% U||100 ppm U|
|Granite||4-5 ppm U|
|Sedimentary rock||2 ppm U|
|Earth’s continental crust (av)||2.8 ppm U|
|Seawater||0.003 ppm U|
According to the OECD redbook, the world consumed 67 kilotonnes (150×10^6 lb) of uranium in 2002. Of that 36 kilotonnes (79×10^6 lb) of was produced from primary sources, with the balance coming from secondary sources, in particular stockpiles of natural and enriched uranium, decommissioned nuclear weapons, the reprocessing of natural and enriched uranium and the re-enrichment of depleted uranium tails.
Platinum as an investment
Platinum has a much shorter history in the financial sector than either gold or silver, which were known to ancient civilizations.
Platinum is relatively scarce even among the precious metals. New mine production totals approximately only 5 million troy ounces (150 Mg) a year. In contrast, gold mine production runs approximately 82 million ounces (2550 Mg) a year, and silver production is approximately 547 million ounces (17000 Mg). As such, it tends to trade at higher per-unit prices.
Platinum is traded on the New York Mercantile Exchange (NYMEX) and the London Platinum and Palladium Market. To be saleable on most commodity markets, platinum ingots must be assayed and hallmarked in a manner similar to the way gold and silver are.
The price of platinum changes along with its supply and demand. During periods of sustained economic stability and growth, the price of platinum tends to be as much as twice the price of gold, whereas, during periods of economic uncertainty, the price of platinum tends to decrease because of reduced demand, falling below the price of gold, partly due to increased gold prices. Platinum price peaked near US$2,300 per troy ounce ($74/g) in March 2008 driven on production concerns (brought about partly due to power delivery problems to South African mines). It subsequently fell to US$780 per troy ounce ($25/g) in November 2008.
Platinum is traded on the London Stock Exchange as an exchange-traded fund under the ticker symbol LSE: PHPT.
Platinum coins are another way to invest in platinum, although relatively few varieties of platinum coins have been minted, due to its cost and difficulty in working.
Most Swiss banks offer platinum accounts where platinum can be instantly bought or sold just like any foreign currency. Unlike physical platinum, the customer does not own the actual metal but rather has a claim against the bank for a certain quantity of metal. Since July 2009 GoldMoney has offered platinum as an alternative to gold and works on a similar principle.
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into “little silver of the Pinto River.” It is in Group 10 of the periodic table of elements. A dense, malleable, ductile, precious, gray-white transition metal, platinum is resistant to corrosion and occurs in some nickel and copper ores along with some native deposits. Platinum is used in jewelry, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and catalytic converters. Platinum bullion has the ISO currency code of XPT. Platinum is a commodity with a value that fluctuates according to market forces. As of 30 October 2009 (2009 -10-30)[update], platinum was worth US$1,324.00 per troy ounce (approximately US$42.57 per gram).
As a pure metal, platinum is silvery-white in appearance, lustrous, ductile, and malleable. It does not oxidize at any temperature, although it is corroded by halogens, cyanides, sulfur, and caustic alkalis. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in aqua regia to form chloroplatinic acid, H2PtCl6.
Platinum’s wear- and tarnish-resistance characteristics are well suited for making fine jewelry. Platinum is more precious than gold or silver. Platinum possesses high resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All of these properties have been exploited for industrial applications.
Platinum has six naturally occurring isotopes: 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt. The most abundant of these is 195Pt, comprising 33.83% of all platinum. 190Pt is the least abundant at only .01%. Of the naturally occurring isotopes, only 190Pt is unstable, though it decays with a half-life of 6.5 × 1011 years. 198Pt undergoes alpha decay, but because its half-life is estimated as being greater than 3.2 × 1014 years, it is considered stable. Platinum also has 31 synthetic isotopes ranging in atomic mass from 166 to 202, making the total number of known isotopes 37. The least stable of these is 166Pt with a half-life of 300 µs, while the most stable is 193Pt with a half-life of 50 years. Most of platinum’s isotopes decay by some combination of beta decay and alpha decay. 188Pt, 191Pt, and 193Pt decay primarily by electron capture. 190Pt and 198Pt have double beta decay paths.
Chemistry and compounds
Platinum’s most common oxidation states are +2, and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species. As is expected, tetracoordinate platinum(II) compounds tend to adopt a square planar geometry. While elemental platinum is generally unreactive, it dissolves in aqua regia to give soluble hexachloroplatinic acid (“H2PtCl6“, formally (H3O)2PtCl6·nH2O ):
- Pt + 4 HNO3 + 6 HCl → H2PtCl6 + 4 NO2 + 4 H2O
This compound has various applications in photography, zinc etchings, indelible ink, plating, mirrors, porcelain coloring, and as a catalyst.
Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate,which is very insoluble in ammonium solutions. Heating the ammonium salt in the presence of hydrogen reduces it to elemental platinum. Platinum is often isolated from ores and recycled thus.Potassium hexachloroplatinate is similarly insoluble, such that the acid has been used in the determination of potassium ions by gravimetry.
When hexachloroplatinic acid is heated, it decomposes through platinum(IV) chloride and platinum(II) chloride to elemental platinum, although the reactions do not occur stepwise, cleanly:
- (H3O)2PtCl6·n H2O PtCl4 + 2 HCl + (n + 2) H2O
- PtCl4 PtCl2 + Cl2
- PtCl2 Pt + Cl2
All three reactions are reversible. Platinum(II) and platinum(IV) bromides are known as well. Platinum hexafluoride is a strong oxidizer capable of oxidising oxygen.
Platinum(IV) oxide, PtO2, also known as Adams’ Catalyst, is a black powder which is soluble in KOH solutions and concentrated acids. PtO2 and the less common PtO both decompose upon heating. Platinum(II,IV) oxide, Pt3O4, is formed in the following reaction:
- 2 Pt2+ + Pt4+ + 4 O2− → Pt3O4
Platinum also forms a trioxide, which is actually in the +4 oxidation state.
Unlike palladium acetate, platinum(II) acetate is not commercially available. Where a base is desired, the halides have been used in conjunction with sodium acetate. The use of platinum(II) acetylacetonate has also been reported.
Zeise’s salt, containing an ethylene ligand, was one of the first organometallic compounds discovered. Dichloro(cycloocta-1,5-diene)platinum(II) is a commercially available olefin complex, which contains easily displaceable cod ligands (“cod” being an abbreviation of 1,5-cyclooctadiene). The cod complex and the halides are convenient starting points to platinum chemistry. As a soft acid, platinum has a great affinity for sulfur, such as on DMSO; numerous DMSO complexes have been reported and care should be taken in the choice of reaction solvent.
Cisplatin, or cis-diamminedichloroplatinum(II) is the first of a series of square planar platinum(II)-containing chemotherapy drugs, including carboplatin and oxaliplatin. These compounds are capable of crosslinking DNA and kill cells by similar pathways to alkylating chemotherapeutic agents.
The hexachloroplatinate ion
The anion of Zeise’s salt
Several barium platinides have been synthesized, in which platinum exhibits negative oxidation states ranging from −1 to −2. These include BaPt, Ba3Pt2, and Ba2Pt. Caesium platinide, Cs2Pt, has been shown to contain Pt2− anions. Platinum is also shown to exhibit negative oxidation states at surfaces reduced electrochemically. The negative oxidation states exhibited by platinum, which are unusual for metallic elements, are believed to be due to the relativistic stabilization of the 6s orbitals.
Platinum output in 2005
Platinum is an extremely rare metal, occurring as only 0.003 ppb in the Earth’s crust. It is sometimes mistaken for silver (Ag).
Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium. Most often the native platinum is found in secondary deposits; platinum is combined with the other platinum group metals in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum group metals. Another large alluvial deposit was found in the Ural Mountains, Russia, which is still mined.
In nickel and copper deposits platinum group metals occur as sulfides (i.e. (Pt,Pd)S)), tellurides (i.e. PtBiTe), antimonides (PdSb), and arsenides (i.e. PtAs2), and as end alloys with nickel or copper. Platinum arsenide, sperrylite (PtAs2), is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. The rare sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with palladium and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex, Gauteng, South Africa.
The largest known primary reserves are in the Bushveld complex in South Africa. The large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin, Canada, are the two other large deposits. In the Sudbury Basin the huge quantities of nickel ore processed makes up for the fact that platinum is present as only 0.5 ppm in the ore. Smaller reserves can be found in the United States, for example in the Absaroka Range in Montana. This is also shown in the production of 2005. In 2005, South Africa was the top producer of platinum with an almost 80% share followed by Russia and Canada.
Platinum exists in higher abundances on the Moon and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on the Earth that are associated with resulting post-impact volcanism, and can be mined economically; the Sudbury Basin is one such example.
Platinum together with the rest of the platinum metals is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper, noble metals such as silver, gold and the platinum group metals as well as selenium and tellurium settle to the bottom of the cell as anode mud, which forms the starting point for the extraction of the platinum group metals.
If pure platinum is found in placer deposits or other ores, it is isolated from them by various methods of subtracting impurities. Because platinum is significantly denser than many of its impurities, the lighter impurities can be removed by simply floating them away in a water bath. Platinum is also non-magnetic, while nickel and iron are both magnetic. These two impurities are thus removed by running an electromagnet over the mixture. Because platinum has a higher melting point than most other substances, many impurities can be burned or melted away without melting the platinum. Finally, platinum is resistant to hydrochloric and sulfuric acids, while other substances are readily attacked by them. Metal impurities can be removed by stirring the mixture in either of the two acids and recovering the remaining platinum.
One suitable method for purification for the raw platinum, which contains platinum, gold, and the other platinum group metals, is to process it with aqua regia, in which palladium, gold and platinum are dissolved, while osmium, iridium, ruthenium and rhodium stay unreacted. The gold is precipitated by the addition of iron(III) chloride and after filtering of the gold, the platinum is precipitated by the addition of ammonium chloride as ammonium chloroplatinate. Ammonium chloroplatinate can be converted to the metal by heating.
Of the 239 tonnes of platinum sold in 2006, 130 tonnes were used for automobile emissions control devices, 49 tonnes were used for jewelry, 13.3 tonnes were used in electronics, and 11.2 tonnes were used by the chemical industry as a catalyst. The remaining 35.5 tonnes produced were used in various other minor applications, such as electrodes, anticancer drugs, oxygen sensors, spark plugs and turbine engines.
The most common use of platinum is as a catalyst in chemical reactions. It has been employed in this application since the early 1800s, when platinum powder was used to catalyze the ignition of hydrogen. The most important application of platinum is in automobiles as a catalytic converter, which allows the complete combustion of low concentrations of unburned hydrocarbon from the exhaust into carbon dioxide and water vapor. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, but especially in catalytic reforming of straight run naphthas into higher-octane gasoline which becomes rich in aromatic compounds. PtO2, also known as Adams’ catalyst, is used as a hydrogenation catalyst, specifically for vegetable oils. Platinum metal also strongly catalyzes the decomposition of hydrogen peroxide into water and oxygen gas.
From 1889 to 1960, the meter was defined as the length of a platinum-iridium (90:10) alloy bar, known as the International Prototype Meter bar. The previous bar was made of platinum in 1799. The International Prototype Kilogram remains defined by a cylinder of the same platinum-iridium alloy made in 1879.
The standard hydrogen electrode also utilizes a platinized platinum electrode due to its corrosion resistance, and other attributes.
Platinum is a precious metal commodity; its bullion has the ISO currency code of XPT. Coins, bars, and ingots are traded or collected. Platinum finds use in jewelry, usually as a 90-95% alloy, due to its inertness and shine. In watchmaking, Vacheron Constantin, Patek Philippe, Rolex, Breitling and other companies use platinum for producing their limited edition watch series. Watchmakers highly appreciate the unique properties of platinum as it neither tarnishes nor wears out.
Average price of platinum from 1991 to 2007 in US$ per troy ounce (~$40/g).
The price of platinum, like other industrial commodities, is more volatile than that of gold. In 2008 the price of platinum ranged from $774 to $2,252 per oz.
During periods of sustained economic stability and growth, the price of platinum tends to be as much as twice the price of gold, whereas during periods of economic uncertainty, the price of platinum tends to decrease due to reduced industrial demand, falling below the price of gold. Gold prices are more stable in slow economic times, as gold is considered a safe haven and gold demand is not driven by industrial uses. In the 18th century, platinum’s rarity made King Louis XV of France declare it the only metal fit for a king.
In the laboratory, platinum wire is used for electrodes; platinum pans are used in thermogravimetric analysis. Platinum is used as an alloying agent for various metal products, including fine wires, noncorrosive laboratory containers, medical instruments, dental prostheses, electrical contacts, and thermocouples. Platinum-cobalt, an alloy of roughly three parts platinum and one part cobalt, is used to make relatively strong permanent magnets.Platinum-based anodes are used in ships, pipelines, and steel piers.
Symbol of prestige
Platinum’s rarity as a metal has caused advertisers to associate it with exclusivity and wealth. “Platinum” debit cards have greater privileges than do “gold” ones. “Platinum awards” are the second highest possible, ranking above “gold”, “silver” and “bronze”, but below diamond. For example, in the United States a musical album that has sold more than 1 million copies, will be credited as “platinum”, whereas an album that sold more than 10 million copies will be certified as “diamond”. Some products, such as blenders and vehicles, with a silvery-white color are identified as “platinum”. Platinum is considered a precious metal, although its use is not as common as the use of gold or silver. The frame of the Crown of Queen Elizabeth the Queen Mother, manufactured for her Coronation as Consort of King George VI, is made of platinum. It was the first British crown to be made of this particular metal.
Platinum occurs naturally in the alluvial sands of various rivers, though there is little evidence of its use by ancient peoples. However, the metal was used by pre-Columbian Americans near modern-day Esmeraldas, Ecuador to produce artifacts of a white gold-platinum alloy. The first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger as a description of an unknown noble metal found between Darién and Mexico, “which no fire nor any Spanish artifice has yet been able to liquefy.”
In 1741, Charles Wood, a British metallurgist, found various samples of Columbian platinum in Jamaica, which he sent to William Brownrigg for further investigation. Antonio de Ulloa, also credited with the discovery of platinum, returned to Spain from the French Geodesic Mission in 1746 after having been there for eight years. His historical account of the expedition included a description of platinum as being neither separable nor calcinable. Ulloa also anticipated the discovery of platinum mines. After publishing the report in 1748, Ulloa did not continue to investigate the new metal. In 1758, he was sent to superintend mercury mining operations in Huancavelica.
In 1750, after studying the platinum sent to him by Wood, Brownrigg presented a detailed account of the metal to the Royal Society, mentioning that he had seen no mention of it in any previous accounts of known minerals. Brownrigg also made note of platinum’s extremely high melting point and refractoriness toward borax. Other chemists across Europe soon began studying platinum, including Torbern Bergman, Jöns Jakob Berzelius, William Lewis, and Pierre Macquer. In 1752, Henrik Scheffer published a detailed scientific description of the metal, which he referred to as “white gold”, including an account of how he succeeded in fusing platinum ore with the aid of arsenic. Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosion.
Carl von Sickingen researched platinum extensively in 1772. He succeeded in making malleable platinum by alloying it with gold, dissolving the alloy in aqua regia, precipitating the platinum with ammonium chloride, igniting the ammonium chloroplatinate, and hammering the resulting finely divided platinum to make it cohere. Franz Karl Achard made the first platinum crucible in 1784. He worked with the platinum by fusing it with arsenic, then later volatilizing the arsenic.
In 1786, Charles III of Spain provided a library and laboratory to Pierre-François Chabaneau to aid in his research of platinum. Chabaneau succeeded in removing various impurities from the ore, including gold, mercury, lead, copper, and iron. This led him to believe that he was working with a single metal, but in truth the ore still contained the yet-undiscovered platinum group metals. This led to inconsistent results in his experiments. At times the platinum seemed malleable, but when it was alloyed with iridium, it would be much more brittle. Sometimes the metal was entirely incombustible, but when alloyed with osmium, it would volatilize. After several months, Chabaneau succeeded in producing 23 kilograms of pure, malleable platinum by hammering and compressing the sponge form while white-hot. Chabeneau realized that the infusibility of platinum would lend value to objects made of it, and so started a business with Joaquín Cabezas producing platinum ingots and utensils. This started what is known as the “platinum age” in Spain.
From 1875 to 1960 the SI unit of length (the standard meter) was defined as the distance between two lines on a standard bar of an alloy of ninety percent platinum and ten percent iridium, measured at 0 degrees Celsius.
In 2007 Gerhard Ertl won the Nobel Prize in Chemistry for determining the detailed molecular mechanisms of the catalytic oxidation of carbon monoxide over platinum (catalytic converter).
Nickel (pronounced /ˈnɪkəl/) is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium. Its use has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite and garnierite, and pentlandite. Major production sites include Sudbury region in Canada, New Caledonia and Norilsk in Russia. The metal is corrosion-resistant, finding many uses in alloys, as a plating, in the manufacture of coins, magnets and common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Enzymes of certain life-forms contain nickel as an active center making the metal essential for them.
Nickel(II) sulfate is produced in large quantities by dissolving nickel metal or oxides in sulfuric acid. This compound is useful for electroplating nickel.
The most common oxidation state of nickel is +2 with several Ni complexes known. It is also thought that a +6 oxidation state may exist, however, this has not been demonstrated conclusively.
Four halides are known to form nickel compounds, these are nickel(II) fluoride, chloride, bromide, and iodide. Nickel(II) chloride is produced analogously by dissolving nickel residues in hydrochloric acid. Tetracarbonylnickel (Ni(CO)4), discovered by Ludwig Mond, is a homoleptic complex of nickel with carbon monoxide. Having no net dipole moment, intermolecular forces are relatively weak, allowing this compound to be liquid at room temperature. Carbon monoxide reacts with nickel metal readily to give this compound; on heating, the complex decomposes back to nickel and carbon monoxide. This behavior is exploited in the Mond process for generating high-purity nickel.
Tetracoordinate nickel(II) takes both tetrahedral and square planar geometries. This is in contrast with the other group 10 elements, which tend to exist as square planar complexes. Bis(cyclooctadiene)nickel(0) is a useful intermediate in organometallic chemistry due to the easily displaced cod ligands. Nickel(III) oxide is used as the cathode in many rechargeable batteries, including nickel-cadmium, nickel-iron, nickel hydrogen, and nickel-metal hydride, and used by certain manufacturers in Li-ion batteries.
Because the ores of nickel are easily mistaken for ores of silver, understanding of this metal and its use dates to relatively recent times. However, the unintentional use of nickel is ancient, and can be traced back as far as 3500 BC. Bronzes from what is now Syria had contained up to 2% nickel. Further, there are Chinese manuscripts suggesting that “white copper” (cupronickel, known as baitung) was used there between 1700 and 1400 BC. This Paktong white copper was exported to Britain as early as the 17th century, but the nickel content of this alloy was not discovered until 1822.
In medieval Germany, a red mineral was found in the Erzgebirge (Ore Mountains) which resembled copper ore. However, when miners were unable to extract any copper from it they blamed a mischievous sprite of German mythology, Nickel (similar to Old Nick) for besetting the copper. They called this ore Kupfernickel from the German Kupfer for copper. This ore is now known to be nickeline or niccolite, a nickel arsenide. In 1751, Baron Axel Fredrik Cronstedt was attempting to extract copper from kupfernickel and obtained instead a white metal that he named after the spirit which had given its name to the mineral, nickel.In modern German, Kupfernickel or Kupfer-Nickel designates the alloy cupronickel.
In the United States, the term “nickel” or “nick” was originally applied to the copper-nickel Indian cent coin introduced in 1859. Later, the name designated the three-cent coin introduced in 1865, and the following year the five-cent shield nickel appropriated the designation, which has remained ever since. Coins of pure nickel were first used in 1881 in Switzerland.
After its discovery the only source for nickel was the rare Kupfernickel, but from 1824 on the nickel was obtained as byproduct of cobalt blue production. The first large scale producer of nickel was Norway, which exploited nickel rich pyrrhotite from 1848 on. The introduction of nickel in steel production in 1889 increased the demand for nickel and the nickel deposits of New Caledonia, which were discovered in 1865, provided most of the world’s supply between 1875 and 1915. The discovery of the large deposits in the Sudbury Basin, Canada in 1883, in Norilsk-Talnakh , Russia in 1920 and in the Merensky Reef, South Africa in 1924 made large-scale production of nickel possible.
The bulk of the nickel mined comes from two types of ore deposits. The first are laterites where the principal ore minerals are nickeliferous limonite: (Fe, Ni)O(OH) and garnierite (a hydrous nickel silicate): (Ni, Mg)3Si2O5(OH). The second are magmatic sulfide deposits where the principal ore mineral is pentlandite: (Ni, Fe)9S8.
In terms of supply, the Sudbury region of Ontario, Canada, produces about 30% of the world’s supply of nickel. The Sudbury Basin deposit is theorized to have been created by a meteorite impact event early in the geologic history of Earth. Russia contains about 40% of the world’s known resources at the Norilsk deposit in Siberia. The Russian mining company MMC Norilsk Nickel obtains the nickel and the associated palladium for world distribution. Other major deposits of nickel are found in New Caledonia, France, Australia, Cuba, and Indonesia. Deposits found in tropical areas typically consist of laterites which are produced by the intense weathering of ultramafic igneous rocks and the resulting secondary concentration of nickel bearing oxide and silicate minerals. Recently, a nickel deposit in western Turkey had been exploited, with this location being especially convenient for European smelters, steelmakers and factories. The one locality in the United States where nickel was commercially mined is Riddle, Oregon, where several square miles of nickel-bearing garnierite surface deposits are located. The mine closed in 1987. In 2005, Russia was the largest producer of nickel with about one-fifth world share closely followed by Canada, Australia and Indonesia, as reported by the British Geological Survey.
Based on geophysical evidence, most of the nickel on Earth is postulated to be concentrated in the Earth’s core. Kamacite and taenite are naturally occurring alloys of iron and nickel. For kamacite the alloy is usually in the proportion of 90:10 to 95:5 although impurities such as cobalt or carbon may be present, while for taenite the nickel content is between 20% and 65%. Kamacite and taenite occur in nickel-iron meteorites.
Extraction and purification
Nickel is recovered through extractive metallurgy. Most sulfide ores have traditionally been processed using pyrometallurgical techniques to produce a matte for further refining. Recent advances in hydrometallurgy have resulted in recent nickel processing operations being developed using these processes. Most sulfide deposits have traditionally been processed by concentration through a froth flotation process followed by pyrometallurgical extraction.
Nickel is extracted from its ores by conventional roasting and reduction processes which yield a metal of greater than 75% purity. Final purification of nickel oxides is performed via the Mond process, which increases the nickel concentrate to greater than 99.99% purity. This process was patented by L. Mond and was used in South Wales in the 20th century. Nickel is reacted with carbon monoxide at around 50 °C to form volatile nickel carbonyl. Any impurities remain solid while the nickel carbonyl gas passes into a large chamber at high temperatures in which tens of thousands of nickel spheres, called pellets, are constantly stirred. The nickel carbonyl decomposes, depositing pure nickel onto the nickel spheres. Alternatively, the nickel carbonyl may be decomposed in a smaller chamber at 230 °C to create fine nickel powder. The resultant carbon monoxide is re-circulated through the process. The highly pure nickel produced by this process is known as carbonyl nickel. A second common form of refining involves the leaching of the metal matte followed by the electro-winning of the nickel from solution by plating it onto a cathode. In many stainless steel applications, 75% pure nickel can be used without further purification depending on the composition of the impurities.
Nickel sulfide ores undergo flotation (differential flotation if Ni/Fe ratio is too low) and then are smelted. After producing the nickel matte, further processing is done via the Sherritt-Gordon process. First copper is removed by adding hydrogen sulfide, leaving a concentrate of only cobalt and nickel. Solvent extraction then efficiently separates the cobalt and nickel, with the final nickel concentration greater than 99%.
The market price of nickel surged throughout 2006 and the early months of 2007; as of April 5, 2007, the metal was trading at 52,300 USD/tonne or 1.47 USD/oz. The price subsequently fell dramatically from these peaks, and as of 19 January 2009 the metal was trading at 10,880 USD/tonne.
The US nickel coin contains 0.04 oz (1.25 g) of nickel, which at the April 2007 price was worth 6.5 cents, along with 3.75 grams of copper worth about 3 cents, making the metal value over 9 cents. Since the face value of a nickel is 5 cents, this made it an attractive target for melting by people wanting to sell the metals at a profit. However, the United States Mint, in anticipation of this practice, implemented new interim rules on December 14, 2006, subject to public comment for 30 days, which criminalize the melting and export of cents and nickels. Violators can be punished with a fine of up to $10,000 and/or imprisoned for a maximum of five years.
As of June 24, 2009 the melt value of a U.S. nickel is $0.0363145 which is less than the face value.
Nickel is used in many industrial and consumer products, including stainless steel, magnets, coinage, rechargeable batteries, electric guitar strings and special alloys. It is also used for plating and as a green tint in glass. Nickel is pre-eminently an alloy metal, and its chief use is in the nickel steels and nickel cast irons, of which there are many varieties. It is also widely used in many other alloys, such as nickel brasses and bronzes, and alloys with copper, chromium, aluminium, lead, cobalt, silver, and gold.
The amounts of nickel used for various applications are 60% used for making nickel steels, 14% used in nickel-copper alloys and nickel silver, 9% used to make malleable nickel, nickel clad, Inconel and other superalloys, 6% used in plating, 3% use for nickel cast irons, 3% in heat and electric resistance alloys, such as Nichrome, 2% used for nickel brasses and bronzes with the remaining 3% of the nickel consumption in all other applications combined. In the laboratory, nickel is frequently used as a catalyst for hydrogenation, most often using Raney nickel, a finely divided form of the metal alloyed with aluminium which adsorbs hydrogen gas. Nickel is often used in coins, or occasionally as a substitute for decorative silver. The American ‘nickel’ five-cent coin is 75% copper and 25% nickel. The Canadian nickel minted at various periods between 1922-81 was 99.9% nickel, and was magnetic. Various other nations have historically used and still use nickel in their coinage.
Nickel is also used in fire assay as a collector of platinum group elements, as it is capable of full collection of all 6 elements, in addition to partial collection of gold. This is seen through the nature of nickel as a metal, as high throughput nickel mines may run PGE recovery (primarily platinum and palladium), such as Norilsk in Russia and the Sudbury Basin in Canada.
Nickel plays numerous roles in the biology of microorganisms and plants, though they were not recognized until the 1970s. In fact urease (an enzyme which assists in the hydrolysis of urea) contains nickel. The NiFe-hydrogenases contain nickel in addition to iron-sulfur clusters. Such [NiFe]-hydrogenases characteristically oxidise H2. A nickel-tetrapyrrole coenzyme, F430, is present in the methyl coenzyme M reductase which powers methanogenic archaea. One of the carbon monoxide dehydrogenase enzymes consists of an Fe-Ni-S cluster. Other nickel-containing enzymes include a class of superoxide dismutase and a glyoxalase.
Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour work week. Nickel sulfide fume and dust is believed to be carcinogenic, and various other nickel compounds may be as well. Nickel carbonyl, [Ni(CO)4], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of the metal as well as the carbonyl’s ability to give off highly toxic carbon monoxide gas, and this one is no exception. It is explosive in air.
Sensitized individuals may show an allergy to nickel affecting their skin, also known as dermatitis. Sensitivity to nickel may also be present in patients with pompholyx. Nickel is an important cause of contact allergy, partly due to its use in jewellery intended for pierced ears. Nickel allergies affecting pierced ears are often marked by itchy, red skin. Many earrings are now made nickel-free due to this problem. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the European Union. In 2002 researchers found amounts of nickel being emitted by 1 and 2 Euro coins far in excess of those standards. This is believed to be due to a galvanic reaction.
It was voted Allergen of the Year in 2008 by the American Contact Dermatitis Society.
Silver, like other precious metals, may be used as an investment. For more than four thousand years, silver has been regarded as a form of money and store of value. However, since the end of the silver standard, silver has lost its role as legal tender in the United States. (It continued to be used in coinage until 1964, when the intrinsic value of the silver overtook the coins’ face values.) (more…)
Copper metal and alloys have been used for thousands of years. In the Roman era, copper was principally mined on Cyprus, hence the origin of the name of the metal as Cyprium, “metal of Cyprus”, later shortened to Cuprum. There may be insufficient reserves to sustain current high rates of copper consumption.Some countries, such as Chile and the United States, still have sizable reserves of the metal which are extracted through large open pit mines.