The Argyle Diamond Mine was a
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 dia ...
located in the East
Kimberley region in the remote north of
Western Australia
Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
. Argyle was at times the largest
diamond
Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...
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
Pink is the color of a namesake flower that is a pale tint of red. It was first used as a color name in the late 17th century. According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, ...
and
red
Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
diamonds (producing over 90% of the world's supply), and additionally provided 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 Rio Tinto, meaning "red river", may refer to:
Businesses
* Rio Tinto (corporation), an Anglo-Australian multinational mining and resources corporation
** Rio Tinto Alcan, based in Canada
** Rio Tinto Borax in America
*** Rio Tinto Borax Mine, a ...
planning to decommission the mine and rehabilitate the site at least through 2025.
The Argyle diamond mine is also notable for being the first successful commercial diamond mine exploiting a
volcanic pipe
Volcanic pipes or volcanic conduits are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. They are considered to be a type of ''diatreme''. Volcanic pipes are composed of a deep, narrow cone of ...
of
lamproite
Lamproite is an ultrapotassic mantle-derived volcanic or subvolcanic rock. It has low CaO, Al2O3, Na2O, high K2O/Al2O3, a relatively high MgO content and extreme enrichment in incompatible elements.
Lamproites are geographically widespread ye ...
, rather than the more usual
kimberlite
Kimberlite is an igneous rock and a rare variant of peridotite. It is most commonly known to be the main host matrix for diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond called the Star of ...
pipe; much earlier attempts to mine diamonds from
a lamproite pipe in
Arkansas
Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...
, United States, were commercially unsuccessful. The Argyle mine is owned by the
Rio Tinto Group
Rio Tinto Group is an Anglo-Australian Multinational corporation, multinational company that is the world's second-largest metals and mining corporation (behind BHP). The company was founded in 1873 when of a group of investors purchased a mine ...
, a diversified mining company which also owns the
Diavik Diamond Mine
The Diavik Diamond Mine is a diamond mine in the North Slave Region of the Northwest Territories, Canada, about northeast of Yellowknife.
Description
Diavik Diamond Mine is an industrial complex set in a remote, subarctic landscape. It consis ...
in Canada and the
Murowa diamond mine
The Murowa list of diamond mines, diamond mine is a diamond mining, mine located in Mazvihwa, south central Zimbabwe, about 40 kilometres from the asbestos mining town of Zvishavane in the Midlands province. The mine is majority owned and operate ...
in Zimbabwe.
Description
The mine site covers about ,
[
]
stretching in a mostly linear shape about long and wide. Argyle originally used
open-pit
Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, is a surface mining technique of extracting rock (geology), rock or minerals from the earth from an open-air pit, sometimes known as a Borrow pit, b ...
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.
[
]
Location
The Argyle diamond mine is located in the
Kimberley region
In geography, regions, otherwise referred to as zones, lands or territories, are areas that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and t ...
in the far northeast of the Australian
state
State may refer to:
Arts, entertainment, and media Literature
* ''State Magazine'', a monthly magazine published by the U.S. Department of State
* ''The State'' (newspaper), a daily newspaper in Columbia, South Carolina, United States
* ''Our S ...
of Western Australia. It is located to the south-west of
Lake Argyle
Lake Argyle is Western Australia's largest and Australia's second largest freshwater man-made reservoir by volume. The reservoir is part of the Ord River Irrigation Scheme and is located near the East Kimberley town of Kununurra. The lake f ...
in the Matsu Ranges, about south-west of
Darwin. Because it is by road from the nearest settlement (
Kununurra), a complete residential camp was constructed on site. Most of the 520 workers commuted from
Perth
Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth is ...
, over away, for alternating two-week shifts at the mine. The mine encouraged local employment and had a large number of indigenous local people working within the mine.
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. Following the discovery of several alluvial diamonds in the West Kimberley region along the Lennard River (Ellendale area) in 1969 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
Tanganyika may refer to:
Places
* Tanganyika Territory (1916–1961), a former British territory which preceded the sovereign state
* Tanganyika (1961–1964), a sovereign state, comprising the mainland part of present-day Tanzania
* Tanzania Main ...
part of the Kalumburu Joint Venture (later to become the Ashton Joint Venture) had employed
Maureen Muggeridge
Maureen Muggeridge (13 August 1948 – 7 October 2010) was a British geologist best known for discovering the Argyle diamond deposit in the north of Western Australia.
Early life and education
Muggeridge was born in Croydon; her father was Eric ...
.
In 1979, Muggeridge discovered diamond samples in the
floodplain
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
of a small creek that flowed in Lake Argyle. She soon traced 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 was commissioned in December 1985.
Geology
The mine was the first successful commercial non
alluvial
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
diamond mine not located on a
kimberlite
Kimberlite is an igneous rock and a rare variant of peridotite. It is most commonly known to be the main host matrix for diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond called the Star of ...
pipe. The pipe is named "AK-1", although it is commonly simply called the "Argyle pipe".
The volcanic pipe is a
diatreme
A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe formed by a gaseous explosion. When magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the ...
, composed of
olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
lamproite
Lamproite is an ultrapotassic mantle-derived volcanic or subvolcanic rock. It has low CaO, Al2O3, Na2O, high K2O/Al2O3, a relatively high MgO content and extreme enrichment in incompatible elements.
Lamproites are geographically widespread ye ...
, present as tuff and lava. Peripheral volcanic facies suggest the lamproite eruption formed a
maar
A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...
. At the margins of the volcanic pipe the lamproite is mixed with a volcanic
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...
containing shattered wall rock fragments mixed and milled by the eruption. Minerals in the marginal facies include
zeolite
Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ・y where is either a metal ion or H+. These pos ...
minerals,
mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
s,
kaolinite
Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral ...
and clays, typical of post-eruption
hydrothermal
Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...
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 the post-eruption cooling of the pipe and converted to
graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...
.
The diatreme pipe formed by explosive eruption of the lamproite magma through a zone of weakness in the
continental crust
Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called ''sial'' be ...
.
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
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.
Production
Argyle was the fourth-largest diamond-producing mine in the world by volume, averaging annual production of . Production peaked in 1994, when were produced. Argyle's open pit mine produced over of rough diamonds.
Most of Argyle's gem-quality production was in
brown diamonds
Brown diamonds are the most common color variety of natural diamonds. In most mines, brown diamonds account for 15% of production. The brown color makes them less attractive to some people as gemstones, and most are used for industrial purposes. H ...
. 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 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 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.
Diamond characteristics
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 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.); 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
Pink is the color of a namesake flower that is a pale tint of red. It was first used as a color name in the late 17th century. According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, ...
and green. Despite 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
Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. It is a crystal that is transparent to opaque and which is generally isotropic (no or very weak birefringence ...
), and have low levels of
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
impurities, their colour resulting instead from structural defects of the
crystal lattice
In geometry and crystallography, a Bravais lattice, named after , is an infinite array of discrete points generated by a set of discrete translation operations described in three dimensional space by
: \mathbf = n_1 \mathbf_1 + n_2 \mathbf_2 + n ...
. Argyle diamonds tend to
fluoresce
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
blue or dull green under
ultraviolet light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
, and blue-white under
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
radiation. The most common inclusion is unconverted
graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...
, followed by crystalline inclusions of orange
garnet
Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.
All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...
,
pyroxene
The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...
, and
olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
.
Annual Diamond Tender
Each year since 1984, 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 of rough pink diamonds produced by the mine, only polished 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 .
[
]
In 2016, the annual Argyle Diamond Tender became the highest-selling tender in its 20-year history, according to the Diamond Investment & Intelligence Center.
[
]
In conjunction with the mine's closure, the 2020 Argyle Tender set further records, as it was the second last such sale.
Following the closure, the final Argyle Diamond Tender in 2021 delivered more record breaking results.
Reserves
Initial proven reserves of the Argyle mine were 61 million
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s of ore, with an average
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
grade of per ore tonne, about . Further estimated reserves of 14 million tonnes of ore, at a grade of 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 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 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, 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 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
Underground hard-rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals, such as ore containing gold, silver, iron, copper, zinc, nickel, tin, and lead. It also involves the ...
), 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 the underground mine commenced in early to mid-2006.
Economics
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 Canad
However, Argyle had two to four times 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.
Underground expansion
In 2005,
Rio Tinto (corporation), 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 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 the latest in mining technology, including
Sandvik
Sandvik AB is a Swedish multinational engineering company specializing in metal cutting, digital and additive manufacturing, mining and construction, stainless and special steel alloys, and industrial heating. The company was founded in Sweden ...
's auto mining technology.
Closure
The mine stopped production on 3 November 2020 after producing approximately 865million 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.
See also
*
Argyle Pink Jubilee
*
Argyle Airport
Argyle Airport is an airport at Lake Argyle, Western Australia. The airport serves the nearby Argyle Diamond Mine.
See also
* List of airports in Western Australia
This is a list of airports in the Australian state of Western Australia. ...
*
Argyle Library Egg
References
Citations
General sources
*
"The Argyle Mine and Its Diamonds" The Gemmological Association of Australia. 2005. Retrieved 2009-10-24.
* Earth Observatory, NASA (2002)
"New Images: Argyle Diamond Mine, Australia" Retrieved 2009-10-24.
*
''VolcanoWorld''. Retrieved 2009-10-24.
External links
Argyle Minesite on InfomineArgyle Pink DiamondsRio Tinto Diamonds"Discovery and Mining of the Argyle Diamond Deposit, Australia" Shigley, Chapman, and Ellison, ''Gems & Gemology'', Spring 2001
Argyle Diamond Investments
{{DEFAULTSORT:Argyle Diamond Mine
Companies based in Western Australia
Diamond mines in Australia
Geology of Western Australia
Kimberley (Western Australia)
Maars of Australia
Proterozoic volcanism
Rio Tinto (corporation) subsidiaries
Surface mines in Australia
Underground mines in Australia
Volcanoes of Western Australia
Mines in Western Australia