Argyle diamond mine 563896 223960729 2008-07-06T18:33:07Z Omphacite 1590117 add sentence with link to lamproite in Arkansas (Crater of Diamonds) {{Unreferenced|date=March 2008}} The '''Argyle [[diamond mine]]''' ({{coor at dms|16|42|44|S|128|23|51|E|type:landmark_region:AU}}) is a [[diamond]] [[mining|mine]] located in the [[Kimberley]] region of [[Western Australia]]. The [[Argyle]] mine is the largest diamond producer in the world by volume, although due to the low proportion of gem-quality diamonds, is not the leader by value. It is the only known significant source of pink diamonds, producing 90 to 95% of the world's supply. The Argyle diamond mine is also notable for being the first successful commercial diamond mine exploiting a [[volcanic pipe]] of [[lamproite]], rather than the more usual [[kimberlite]] pipe. Much earlier commercial attempts to mine diamonds from a lamproite pipe in Arkansas in the southern United States were unsuccessful; the lamproite pipe there is now contained within the [[Crater of Diamonds State Park]]. The Argyle mine is owned by the [[Rio Tinto Group]], a diversified mining company which also owns the [[Diavik Diamond Mine]] in [[Canada]] and the [[Murowa diamond mine]] in [[Zimbabwe]]. ==Description== [[Image:Argyle mine false color.jpg|thumb|350px|A false-color [[NASA]] image of the Argyle mine. Blue colours show the location of the mine and its depressed elevation as a result of the open pit mining technique.]] The mine covers about 450,000 [[square metre]]s (110 acres), stretching in a mostly linear shape about 1600 [[metre]]s (5,200 ft) long and 150 to 600 metres (500 to 2,000 ft) wide. The mine is of [[open pit mine|open pit]] construction, and reaches about 600 metres (1,900 ft) deep at its deepest point. ===Location=== The Argyle diamond mine is located in the [[Kimberley region of Western Australia|Kimberley]] [[Regions of Western Australia|region]] in the far northeast of the [[Australia]]n [[states of Australia|state]] of [[Western Australia]]. It is located to the southwest of [[Lake Argyle, Western Australia|Lake Argyle]] in the [[Matsu Ranges]], about 550 kilometres (340 miles) southwest of [[Darwin, Northern Territory|Darwin]]. Because the mine is located about 120 kilometres (75 miles) from the nearest settlement ([[Kununurra, Western Australia|Kununurra]]), a complete residential camp has been constructed on site. Most of the 520 workers commute from [[Perth, Western Australia|Perth]] (over 2,000 kilometres, or 1,200 miles, away) for alternating two week shifts at the mine. The mine has encouraged local employment and has a large number of indigenous local people working within the mine. ===Geology=== The mine is the first successful commercial diamond mine (except [[alluvium|alluvial]] mining operations) not located on a [[kimberlite]] pipe. The pipe is named "AK-1", although it is commonly simply called the "Argyle pipe". The volcanic pipe is a [[diatreme]], composed of [[olivine]] [[lamproite]], present as tuff and lava. Peripheral volcanic facies suggest the lamproite eruption formed a [[maar]]. At the margins of the volcanic pipe the lamproite is mixed with a volcanic [[breccia]] containing shattered wall rock fragments mixed and milled by the eruption. Minerals in the marginal facies include [[zeolite]] minerals, [[mica]]s, [[kaolinite]] and clays, typical of post-eruption [[hydrothermal]] circulation. Diamonds are found within the intact core of the volcanic pipe, as well as within some of the marginal breccia facies and maar facies. However, some diamonds are considered to have been resorbed during the post-eruption cooling of the pipe and converted to [[graphite]]. The diatreme pipe formed by explosive eruption of the lamproite magma through a zone of weakness in the [[continental crust]]. The diamonds found at the Argyle pipe have been dated to about 1.58 billion years of age, while the volcano which created the pipe is aged between 1.1 and 1.2 billion years old. This represents a relatively short period during which diamond formation could have taken place (around 400 million years), which may explain the small average size and unusual physical characteristics of Argyle diamonds. Diamonds found in the Argyle pipe are predominantly ''[[eclogite|eclogitic]]'', meaning that the carbon is of organic origin (see [[Diamond#Natural history|Natural history of diamonds]]). In addition to the pipe itself, there are a number of semi-permanent streams that have eroded away portions of the pipe and created significant alluvial deposits of diamonds. These deposits are also actively mined. ==Production== The Argyle diamond mine leads the world in volume production of diamond, averaging annual production of 35 million [[Carat (mass)|carat]]s (7,000 [[kilogram|kg]]), or about one third of global production of natural diamonds. Production peaked in 1994, when 42 million carats (8,400 kg) were produced. Of this quantity only 5% is considered gem-quality, with the rest being either near-gem quality or industrial grade; this is somewhat below world averages of about 20% of mined diamonds qualifying as gem-grade. Since the mine's opening in 1985, it has produced over 600 million carats (120,000 kg) of diamonds. Most of Argyle's gem quality production is in brown diamonds. These diamonds are usually difficult to sell, although Rio Tinto has seen some success in a decade-long marketing campaign to promote brown diamonds as [[champagne (color)|champagne]] and [[cognac]] toned. In contrast, the company has no problems selling pink and red diamonds, which are very rare and in high demand, therefore commanding premium prices. The pink diamonds are processed and sold as polished diamonds by a specialised team based in Perth to customers world wide. The highlight of the coloured diamond industry calendar is the annual Pink Diamond Tender. Access to its collector's edition catalogue and website access in itself is highly sought after. The mine has ore processing and diamond sorting facilities on site. Once diamonds are removed from the ore and acid washed, they are sorted and shipped to Perth for further sorting and sale. A significant quantity of diamonds are cut in [[India]], where low costs of labor allow small diamonds to be cut for a profit; this is especially relevant to the Argyle mine, which on average produces smaller rough diamonds than other mines do. ===Diamond characteristics=== The diamonds produced at the Argyle diamond mine are of an average low quality. Only 5% of mined diamonds are of gem quality, compared to a worldwide average of 20%; of the remaining 95%, they are about evenly split between classifications of "near gem quality" and industrial grade. 80% of Argyle diamonds are brown, followed by 16% yellow, 2% white, 2% grey, and less than 1% pink and green. Despite the low production volume of pink and red diamonds, the Argyle mine is the only reliable source in the world, producing 90 to 95% of all pink and red diamonds. Most Argyle diamonds are classified as type 1a (see [[material properties of diamond]]), and have low levels of [[nitrogen]] impurities, their colour resulting instead from structural defects of the [[crystal lattice]]. Argyle diamonds tend to [[fluorescence|fluoresce]] blue or dull green under [[ultraviolet light]], and blue-white under [[X-ray]] radiation. The most common inclusion is unconverted [[graphite]], followed by crystalline inclusions of orange [[garnet]], [[pyroxene]], and [[olivine]]. ===Reserves=== Initial proven reserves of the Argyle mine were 61 million [[metric ton|tonne]]s of ore, with an average [[ore grade]] of 6.8 carats (1.36 g) ''per'' or tonne, about 400 million carats (80,000 kg). Further estimated reserves of 14 million tonnes of ore, at a grade of 6.1 carats (1.22 g) ''per'' tonne (85 million carats, 17,000 kg), also existed. [[As of 2001]], reserves and resources in the open-pit mined area contain 220 million tonnes of 2.5 to 3.0 carat (500 to 600 mg) per tonne graded ore, sufficient to sustain current production rates until 2007. The ore grades at the Argyle mine are unusually high, with most commercial diamond mines averaging grades of 0.3 to 1.0 carats (60 to 200 mg) per metric ton. Alluvial deposits of diamonds are believed to have been exhausted. In 1995, drilling samples taken from about 300 metres below the floor of the pit indicated the possible presence of about 100 million tons of ore, with an estimated grade of 3.7 carats (740 mg) per ton. In 1998, it was decided to instead move mining operations toward the west ridge of the mine, where 64 million tons of ore graded at 2.6 carats (520 mg) per ton are located. An exploration decline was constructed at a cost of [[Australian dollar|A$]]70 million to evaluate the economics of mining [[diamond]]s from the diamoniferous pipes below the floor of the open pit; these reserves would be mined underground (''via'' block caving), rather than the open pit method currently used. In late-2005 Rio Tinto Ltd concluded that the operation was economically feasible. Pre-production construction of the underground mine commenced in early to mid 2006 === Economics === The Argyle diamond mine is economically feasible because its large reserves and high grade ore offsets a low average diamond weight value. The estimated value of Argyle diamond production is only [[USD|US$]]7 ''per'' carat (US$35/g); this compares to values of 70 USD per carat ($350/g) for diamonds produced at the [[Diavik Diamond Mine|Diavik mine]] and US$170 ''per'' carat (US$850/g) at the [[Ekati Diamond Mine|Ekati mine]], both in [[Canada]].[http://www.goldismoney.info/forums/showpost.php?p=6226&postcount=3] However, Argyle has two to four times the concentration of diamonds (ore grade) of these mines. This makes extraction economically feasible, as mine costs are mostly related to the amount of ore processed, not the amount of diamond extracted. ==[[Block Caving]]== Project In 2005 [[Rio Tinto]] given the go ahead to a future expantion project of the Argyle Mine moving it from an open pit to an underground mine. The project is predominantly an underground construction project requiring high quality development and engineering excellence. The Bock Cave is expected to operate until [[2018]] using the latest in mining technology, including [[Sandvik]]'s auto mining technology. The project to date has experienced managerial issues resulting in the change of contractor from [[Roch]] to [[Macmahon_Holdings_Ltd|Macmahon]] and is now due to be completed by [[2010]]. ==History== Small quantities of alluvially deposited diamonds have been known in Australia since the late 19th century, first found by prospectors searching for [[gold]]. However, no source volcanic pipe deposit was apparent. A systematic search of Western Australia for the source of these diamonds began in 1969, and on [[October 2]], [[1979]], the Argyle pipe was discovered. Over the following three years, the deposit was assessed for economic viability, and in 1983 the decision was made to commence mining operations. Alluvial mining operations commenced immediately, while the open pit mine was constructed over a period of 18 months at a cost of A$450 million. The mine was commissioned in December 1985. ==References== <!-- ---------------------------------------------------------- See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for a discussion of different citation methods and how to generate footnotes using the <ref>, </ref> and <reference /> tags ----------------------------------------------------------- --> <div class="references-small"> <references /> * Chapman, J. et al. (1996). [http://www.gem.org.au/gallery/diamond.htm "The Argyle Mine and Its Diamonds"] (adapted from Chapman). Australian Gemmologist 19, pp. 339-346. * Earth Observatory, NASA (2002). [http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16466 "New Images: Argyle Diamond Mine, Australia"]. Retrieved March 17, 2005. * Mining-technology.com. [http://www.mining-technology.com/projects/argyle/ "Rio Tinto: Argyle Diamond Mine, Kimberley, Australia"]. Retrieved March 17, 2005. * Shigley, James E; Chapman, John; and Ellison, Robyn K. [http://www.argylediamonds.com.au/pdfs/gems_and_gemology.pdf "Discovery and Mining of the Argyle Mine Deposit, Australia"]. ''Gems & Gemology'': Spring 2001. * [http://www.riotintodiamonds.com Rio Tinto Diamonds] Retrieved March 17, 2005. * [http://www.costellos.com.au/diamonds/industry.html "The Australian Diamond Industry"] Retrieved March 17, 2005. * [http://www.goldismoney.info/forums/showpost.php?p=6226&postcount=3 "Gold and Silver Forum".] Retrieved March 22, 2005. * [http://volcano.und.edu/vwdocs/volc_images/australia/argyle/argyle.html "Argyle Diamond Pipe, Western Australia"] Retrieved June 1st, 2008. </div> ==External links== *[http://www.infomine.com/minesite/minesite.asp?site=argyle Argyle Minesite on Infomine] *[http://www.argylediamonds.com.au Argyle Diamonds homepage] ''Several of this article's references contain excellent maps and photographs of the mine and examples of diamonds produced there, which cannot be placed in this article due to [[copyright]] limitations. The reader is especially directed to Shigley, Chapman, and Ellison's article, ''[http://www.argylediamonds.com.au/pdfs/gems_and_gemology.pdf Gems & Gemology]'' [[Category:Diamond mines in Australia]] [[Category:Geography of Western Australia]] [[Category:Geology of Western Australia]] [[Category:Companies based in Perth]]