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51-493: The Argyle Diamond Mine was a diamond mine located in the East Kimberley region in the remote north of Western Australia . Argyle was at times the largest diamond producer in the world by volume (14 million carats in 2018), although the proportion of gem-quality diamonds was low. It was the only known significant source of pink and red diamonds (producing over 90% of the world's supply), and additionally provided

102-582: A body of mantle rocks on Zabargad Island in the Red Sea . Olivine occurs in both mafic and ultramafic igneous rocks and as a primary mineral in certain metamorphic rocks . Mg-rich olivine crystallizes from magma that is rich in magnesium and low in silica . That magma crystallizes to mafic rocks such as gabbro and basalt . Ultramafic rocks usually contain substantial olivine, and those with an olivine content of over 40% are described as peridotites . Dunite has an olivine content of over 90% and

153-495: A cheap way to sequester CO 2 . The presence of iddingsite on Mars would suggest that liquid water once existed there, and might enable scientists to determine when there was last liquid water on the planet. Because of its rapid weathering, olivine is rarely found in sedimentary rock . Norway is the main source of olivine in Europe, particularly in an area stretching from Åheim to Tafjord , and from Hornindal to Flemsøy in

204-535: A decade-long marketing campaign to promote brown diamonds as champagne and cognac toned. In contrast, the company has no problems selling diamonds in pink, purple and red tones, which are very rare and in high demand, therefore commanding premium prices. The pink diamonds were processed and sold as polished diamonds by a specialised team based in Perth to customers worldwide. The mine had ore processing and diamond sorting facilities on site. Once diamonds were removed from

255-618: A depth of about 410 km (250 mi) within Earth. Because it is thought to be the most abundant mineral in Earth's mantle at shallower depths, the properties of olivine have a dominant influence upon the rheology of that part of Earth and hence upon the solid flow that drives plate tectonics . Experiments have documented that olivine at high pressures (12  GPa , the pressure at depths of about 360 km (220 mi)) can contain at least as much as about 8900 parts per million (weight) of water, and that such water content drastically reduces

306-446: A depth of about 660 km (410 mi), ringwoodite decomposes into silicate perovskite ( (Mg,Fe)SiO 3 ) and ferropericlase ( (Mg,Fe)O ) in an endothermic reaction. These phase transitions lead to a discontinuous increase in the density of the Earth's mantle that can be observed by seismic methods. They are also thought to influence the dynamics of mantle convection in that the exothermic transitions reinforce flow across

357-411: A general position. At the high temperatures and pressures found at depth within the Earth the olivine structure is no longer stable. Below depths of about 410 km (250 mi) olivine undergoes an exothermic phase transition to the sorosilicate , wadsleyite and, at about 520 km (320 mi) depth, wadsleyite transforms exothermically into ringwoodite , which has the spinel structure. At

408-653: 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-per-tonne (500 to 600 mg) 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 carat (60 to 200 mg) per metric ton. Alluvial deposits of diamonds are believed to have been exhausted. In 1989–1990, drill samples were taken from over 300 m below

459-431: A hexagonal, close-packed array of oxygen ions with half of the octahedral sites occupied with magnesium or iron ions and one-eighth of the tetrahedral sites occupied by silicon ions. There are three distinct oxygen sites (marked O1, O2 and O3 in figure 1), two distinct metal sites (M1 and M2) and only one distinct silicon site. O1, O2, M2 and Si all lie on mirror planes , while M1 exists on an inversion center. O3 lies in

510-593: A large number of indigenous local people working within the mine. 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. Following the discovery of several alluvial diamonds in the West Kimberley region along the Lennard River (Ellendale area) in 1969

561-458: A large proportion of other naturally coloured diamonds, including champagne, cognac and rare blue diamonds. Mining operations ceased in November 2020, after 37 years of operations and producing more than 865 million carats of rough diamonds. Mine operator Rio Tinto plans to decommission the mine and rehabilitate the site at least through 2025. The Argyle diamond mine is also notable for being

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612-560: A mostly linear shape about 1,600 m (5,200 ft) long and 150 to 600 m (490 to 1,970 ft) wide. Argyle originally used open-pit techniques, reaching about 600 m deep at its deepest point. The open cut closed in 2010, and operations became fully underground in 2013 via block cave mining . The Argyle diamond mine is located in the Kimberley region in the far northeast of the Australian state of Western Australia. It

663-592: A result of traces of nickel , though it may alter to a reddish color from the oxidation of iron. Translucent olivine is sometimes used as a gemstone called peridot ( péridot , the French word for olivine). It is also called chrysolite (or chrysolithe , from the Greek words for gold and stone), though this name is now rarely used in the English language. Some of the finest gem-quality olivine has been obtained from

714-643: A systematic search of Western Australia for the source of these diamonds was begun by a consortium of mining companies, collectively known as the Kalumburu Joint Venture. Tanganyika Holdings part of the Kalumburu Joint Venture (later to become the Ashton Joint Venture) had employed Maureen Muggeridge . In 1979, Muggeridge discovered diamond samples in the floodplain of a small creek that flowed in Lake Argyle. She soon traced

765-409: A worldwide average of 20%. (Author Janine Roberts contends that the "near-gem quality" rating is subjective and misleading because these diamonds can be cut into gems if desired.) The remaining 95% 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

816-572: Is also at least one example of a heritage diamond mine ( Crater of Diamonds State Park ). Kao diamond mine, Lesotho Olivine The ratio of magnesium to iron varies between the two endmembers of the solid solution series: forsterite (Mg-endmember: Mg 2 Si O 4 ) and fayalite (Fe-endmember: Fe 2 Si O 4 ). Compositions of olivine are commonly expressed as molar percentages of forsterite (Fo) and/or fayalite (Fa) ( e.g. , Fo 70 Fa 30 , or just Fo 70 with Fa 30 implied). Forsterite's melting temperature

867-474: Is likely a cumulate formed by olivine crystallizing and settling out of magma or a vein mineral lining magma conduits. Olivine and high pressure structural variants constitute over 50% of the Earth's upper mantle, and olivine is one of the Earth's most common minerals by volume. The metamorphism of impure dolomite or other sedimentary rocks with high magnesium and low silica content also produces Mg-rich olivine, or forsterite . Fe-rich olivine fayalite

918-505: Is located to the south-west of Lake Argyle in the Matsu Ranges, about 550 km (340 mi) south-west of Darwin . Because it is 185 km (115 mi) by road from the nearest settlement ( Kununurra ), a complete residential camp was constructed on site. Most of the 520 workers commuted from Perth , over 2,000 km (1,200 mi) away, for alternating two-week shifts at the mine. The mine encouraged local employment and had

969-477: Is reflected in several local names with "red" such as Raudbergvik (Red rock bay) or Raudnakken (Red ridge). Hans Strøm in 1766 described the olivine's typical red color on the surface and the blue color within. Strøm wrote that in Norddal district large quantities of olivine were broken from the bedrock and used as sharpening stones . Kallskaret near Tafjord is a nature reserve with olivine. Olivine

1020-410: Is relatively much less common, but it occurs in igneous rocks in small amounts in rare granites and rhyolites , and extremely Fe-rich olivine can exist stably with quartz and tridymite . In contrast, Mg-rich olivine does not occur stably with silica minerals, as it would react with them to form orthopyroxene ( (Mg,Fe) 2 Si 2 O 6 ). Mg-rich olivine is stable to pressures equivalent to

1071-483: Is unconverted graphite , followed by crystalline inclusions of orange garnet , pyroxene , and olivine . Each year from 1984 to 2021, a small collection of the best pink diamonds was offered in an exclusive, invitation-only, sale known as the Argyle Pink Diamond Tender. For every 1 million carats (200 kg) of rough pink diamonds produced by the mine, only 1 carat (0.20 g) polished

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1122-418: Is unusually high at atmospheric pressure, almost 1,900 °C (3,450 °F), while fayalite's is much lower – about 1,200 °C (2,190 °F). Melting temperature varies smoothly between the two endmembers, as do other properties. Olivine incorporates only minor amounts of elements other than oxygen (O), silicon (Si), magnesium (Mg) and iron (Fe). Manganese (Mn) and nickel (Ni) commonly are

1173-558: Is used as a substitute for dolomite in steel works. The aluminium foundry industry uses olivine sand to cast objects in aluminium. Olivine sand requires less water than silica sands while still holding the mold together during handling and pouring of the metal. Less water means less gas (steam) to vent from the mold as metal is poured into the mold. In Finland, olivine is marketed as an ideal rock for sauna stoves because of its comparatively high density and resistance to weathering under repeated heating and cooling. Gem-quality olivine

1224-737: The Sunnmøre district. There is also olivine in Eid municipality. About 50% of the world's olivine for industrial use is produced in Norway. At Svarthammaren in Norddal olivine was mined from around 1920 to 1979, with a daily output up to 600 metric tons. Olivine was also obtained from the construction site of the hydro power stations in Tafjord. At Robbervika in Norddal municipality an open-pit mine has been in operation since 1984. The characteristic red color

1275-473: The orthorhombic P Bravais lattice , which arise from each silica (SiO 4 ) unit being joined by metal divalent cations with each oxygen in SiO 4 bound to three metal ions. It has a spinel -like structure similar to magnetite but uses one quadrivalent and two divalent cations M 2 M O 4 instead of two trivalent and one divalent cations. Olivine is named for its typically olive-green color, thought to be

1326-401: The additional elements present in highest concentrations. Olivine gives its name to the group of minerals with a related structure (the olivine group ) – which includes tephroite ( Mn 2 SiO 4 ), monticellite ( Ca MgSiO 4 ), larnite (Ca 2 SiO 4 ) and kirschsteinite (CaFeSiO 4 ) (commonly also spelled kirschteinite ). Olivine's crystal structure incorporates aspects of

1377-502: The concentration of diamonds (ore grade) of these mines. This made extraction economically feasible, as mine costs are mostly related to the amount of ore processed, not the amount of diamond extracted. In 2005, Rio Tinto was given the go-ahead to a future expansion project, moving it from an open pit to an underground mine. This plan was postponed; in September 2010 Rio Tinto announced fresh plans to develop an underground mine beneath

1428-442: The decision was made to remove or "cut back" the unstable part of the west wall which freed up further economic ore in the south part of the open pit. This cut back cost around $ 100 million. Argyle announced on 2 March 2018 that its estimated Ore Reserves decreased by 13 million tonnes to just 16 million tonnes. They mined 5 million tonnes in 2017. A more conservative view on future production performance and grades could bring forward

1479-401: The early Solar System ; and pallasites , mixes of iron-nickel and olivine. The rare A-type asteroids are suspected to have a surface dominated by olivine. The spectral signature of olivine has been seen in the dust disks around young stars. The tails of comets (which formed from the dust disk around the young Sun ) often have the spectral signature of olivine, and the presence of olivine

1530-435: The economic shut-off criteria. An exploration decline was constructed at a cost of A$ 70 million to evaluate the economics of mining diamonds from the diamondiferous pipes below the floor of the open pit; these reserves would be mined underground (by block caving ), rather than the open-pit method used up to then. In late 2005, Rio Tinto Ltd concluded that the operation was economically feasible. Pre-production construction of

1581-404: The existing pit, increasing annual production to 9 million tonnes of ore. The project was completed by 2013, however with more expensive operations to run deeper mining, the mining costs soon began to outweigh the diamond yield. The project was predominantly an underground construction requiring high-quality development and engineering excellence. The Block Cave operated until the end of 2020 using

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1632-532: The final diamonds mined continued into 2022 in both Australia and the United States. Diamond mine There are a limited number of commercially available diamond mines currently operating in the world, with the 50 largest mines accounting for approximately 90% of global supply. Diamonds are also mined alluvially over disperse areas, where diamonds have been eroded out of the ground, deposited, and concentrated by water or weather action. There

1683-853: The first successful commercial diamond mine exploiting a volcanic pipe of lamproite , rather than the more usual kimberlite pipe; much earlier attempts to mine diamonds from a lamproite pipe in Arkansas , United States, were commercially unsuccessful. 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. The mine site covers about 50 ha (124 acres), stretching in

1734-408: The floor of the pit. At the end of 1989 around 238 million tons of ore, with an estimated grade of 3.7 carats per ton were quoted as a resource. Much of this resource was below the open pit and was the subject of an underground mining study carried out in the mid-1990s. In the late 1990s, part of the west wall of the open pit mine, containing 25 million tonnes of waste rock, began to collapse. In 1998,

1785-411: The iron content decreases the pressure of the phase transition and narrows the wadsleyite stability field. At about 0.8 mole fraction fayalite, olivine transforms directly to ringwoodite over the pressure range 10.0 to 11.5 GPa (99,000–113,000 atm). Fayalite transforms to Fe 2 SiO 4 spinel at pressures below 5 GPa (49,000 atm). Increasing the temperature increases

1836-418: The latest in mining technology, including Sandvik 's auto mining technology. Following an announcement in 2018 that it was no longer economically viable, the mine stopped production on 3 November 2020 after producing approximately 865   million carats with remaining ores processed for the next six months followed by a decade of restoration in conjunction with the traditional owners of the lands. Sales of

1887-522: The low production volume of pink and red diamonds, the Argyle mine was 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 fluoresce blue or dull green under ultraviolet light , and blue-white under X-ray radiation. The most common inclusion

1938-506: 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, micas , kaolinite and clays, typical of post-eruption hydrothermal circulation. Diamonds were 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

1989-437: The mine's closure, the 2020 tender set further records, as it was the second last such sale. Following the closure, the final tender in 2021 delivered more record breaking results. Initial proven reserves of the Argyle mine were 61 million tonnes of ore, with an average ore grade of 6.8 carats (1.36 g) per ore tonne, about 400 million carats (80,000 kg). Further estimated reserves of 14 million tonnes of ore, at

2040-529: The ore and acid washed, they were sorted and shipped to Perth for further sorting and sale. A significant quantity of diamonds were cut in India, where low costs of labour allowed small diamonds to be cut for a profit; this was especially relevant to the Argyle mine, which on average produced smaller rough diamonds than other mines. The diamonds produced at the Argyle diamond mine were of an average low quality. Only 5% of mined diamonds were of gem quality, compared to

2091-399: The phase boundary, whereas the endothermic reaction hampers it. The pressure at which these phase transitions occur depends on temperature and iron content. At 800 °C (1,070 K; 1,470 °F), the pure magnesium end member, forsterite, transforms to wadsleyite at 11.8 gigapascals (116,000  atm ) and to ringwoodite at pressures above 14 GPa (138,000 atm). Increasing

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2142-515: 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

2193-465: The pressure of these phase transitions. Olivine is one of the less stable common minerals on the surface according to the Goldich dissolution series . It alters into iddingsite (a combination of clay minerals, iron oxides and ferrihydrite ) readily in the presence of water. Artificially increasing the weathering rate of olivine, e.g. by dispersing fine-grained olivine on beaches, has been proposed as

2244-606: The resistance of olivine to solid flow. Moreover, because olivine is so abundant, more water may be dissolved in olivine of the mantle than is contained in Earth's oceans. Olivine pine forest (a plant community ) is unique to Norway. It is rare and found on dry olivine ridges in the fjord districts of Sunnmøre and Nordfjord. Mg-rich olivine has also been discovered in meteorites , on the Moon and Mars , falling into infant stars, as well as on asteroid 25143 Itokawa . Such meteorites include chondrites , collections of debris from

2295-438: The small average size and unusual physical characteristics of Argyle diamonds. Diamonds found in the Argyle pipe are predominantly eclogitic , meaning that the carbon is of organic origin (see Natural history of diamonds ). In addition to the pipe itself, a number of semi-permanent streams have eroded away portions of the pipe and created significant alluvial deposits of diamonds. These deposits were also actively mined. Argyle

2346-415: The source of the diamonds to the headwaters of Smoke Creek. On 2 October 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

2397-569: The underground mine commenced in early to mid-2006. The Argyle diamond mine was economically feasible because its large reserves and high-grade ore offset a low average diamond value. The estimated value of Argyle diamond production was only US$ 7 per carat ($ 35/g); this compared to values of $ 70 per carat ($ 350/g) for diamonds produced at the Diavik mine and US$ 170 per carat ($ 850/g) at the Ekati mine , both in Canada. However, Argyle had two to four times

2448-460: Was commissioned in December 1985. The mine was the first successful commercial non alluvial diamond mine 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

2499-519: Was offered for sale at the tender. In March 2009, Argyle announced their first tender of rare blue diamonds. The "Once in a Blue Moon" collection was sourced over several years, and comprised a range of precious blue and violet diamonds, which weighed in total 287 carats (57.4 g). In 2016, the tender became the highest-selling tender in its 20-year history, according to the Diamond Investment & Intelligence Center. In conjunction with

2550-480: Was the fourth-largest diamond-producing mine in the world by volume, averaging annual production of 8 million carats (1,600 kg). Production peaked in 1994, when 42 million carats (8,400 kg) were produced. Argyle's open pit mine produced over 750 million carats (150,000 kg) of rough diamonds. Most of Argyle's gem-quality production was in brown diamonds . These diamonds are usually difficult to sell, although Rio Tinto has seen some success in

2601-458: Was verified in samples of a comet from the Stardust spacecraft in 2006. Comet-like (magnesium-rich) olivine has also been detected in the planetesimal belt around the star Beta Pictoris . Minerals in the olivine group crystallize in the orthorhombic system ( space group P bnm ) with isolated silicate tetrahedra, meaning that olivine is a nesosilicate . The structure can be described as

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