Saturday, November 13, 2010
Diamond Deposits: Distribution & Production
DISTRIBUTION & PRODUCTION
Diamonds are mined from at least 20 countries; the leading producers of natural diamond are
, Australia , Botswana , Canada , South Africa and Russia . The World Diamond Council estimated that natural diamond production in 1999 was more than 111 million carats valued at $7.4 billion ( Zaire ). In 2000, diamond production was estimated at 110 million carats valued at $7.9 billion ( US ), and in 2001, the Mining Journal estimated that 110 million carats were mined with an estimated value of $7.3 billion ( US ). The Northern Miner (v.90, no.1) reported rough diamond sales in 2003 for the Diamond Trading Company (DeBeers Marketing Arm) was $5.52 billion. It is extraordinary to note that US ranked 6th in diamond production during this period and was expected to surpass Canada in the second quarter of 2004, particularly when it is realized that prior to 1998, South Africa did not have a diamond industry. This is one of the great exploration success stories of the 20th century (Krajick, 2001). Canada
Industrial diamonds have considerably less value than gem diamond and much industrial production is synthetic. In 2001, nearly 70% of the total natural and synthetic industrial diamond production came from
, Ireland , and the Russia : 92% was synthetic (Olson, 2001). According to the US Geological Survey, world production of natural industrial diamond totaled 48 million carats in 2001 and 48.9 million carats in 2002. Over one-third of the world’s natural diamond production was classified as industrial. However, this represented only a very small percentage (~1%) of the total monetary value of natural diamond production. Australia led the market in recovery of natural industrial diamonds and has averaged 22.1 million carats per year; however, declining reserves at the Argyle mine resulted in Australian industrial diamond production of only 13.1 million carats in 2001 and in 2002 (Olson, 2003) United States
The World Diamond Council reported that the
was the largest producer of synthetic industrial diamonds with 125 million carats manufactured in 1999. The US Geological Survey reported that domestic synthetic industrial diamond production for 2002 was 310 million carats. The total industrial output worldwide was estimated to be in excess of 800 million carats in 2001 valued at more than $600 million (Olson, 2001). Domestic synthetic diamonds were produced by two companies: GE Superabrasives in US and Mypodiamond, Inc., in Ohio . New Jersey
Natural diamond production was dominated by southern African countries with a significant contribution by
and Russia . Nearly all of the Australian diamond production was from the Argyle mine, which accounted for more than 20% of world’s diamonds. However, the relatively low quality of the Argyle diamonds rendered the production to be less valuable than some smaller operations elsewhere (Table 1). Australia
Table 1: Estimated 2001 World Diamond Production*
Country Carats (x 103) Value ($ millions)
D.R. Congo 19,637 496
Total 110,176 7,253
*Source: Mining Journal,
, London August 23, 2002
Although there are hundreds of known diamond occurrences around the world, commercial diamond deposits are rare. In the richest, diamond occurs in concentrations of much less than 1 part per million (Lampietti and Sutherland, 1978). The few commercial diamond deposits are hosted by kimberlite, lamproite, and placers derived from these host rocks. These are all associated with Archean cratons and cratonized Proterozoic belts. However, the discovery of several unconventional host rocks in recent years, some with very high ore grades, suggests that other rock types and geological environments will become diamond targets in the future (Hausel, 1996; Erlich and Hausel, 2002).
The world’s natural diamonds are produced from a small group of deposits, which typically have operating lives of 20 to 30 years. A notable exception is the Premier mine (
), which potentially could operate for more than 100 years (Levinson and others, 1992). South Africa
Table 2: Diamond Production of Major Mines in 2001**
Country Carats Tonnes US$/carat Value
(‘000) (‘000) ($ m)
Ekati 3,685 3,685 144 531
Jwaneng 12,339 8,920 110 1,357
Orapa 13,056 15,779 50 653
Letlhakane 1,021 3,625 180 184
Finsch 2,465 4,768 70 173
Premier 1,637 3,102 75 123
Baken 65 5,835 400 26
Koffiefontein 145 2,299 225 33
Udachnaya 11,500 9,000 85 978
Jubilee 5,500 9,100 65 358
Argyle 26,000 15,100 11 286
Merlin 70 270 110 8
Namdeb Onshore 1,385 21,867 220 305
**Source: Mining Journal,
, London August 23, 2002
The Orange River basin with its many tributaries drain a region with more than 3000 known barren and diamondiferous kimberlite pipes that include some of the richest pipes in the world. The principal diamond producing countries in Africa include Angola, Botswana, Central African Republic, Congo Republic (Zaire), Ghana, Guinea, Namibia, Sierra Leone, South Africa and Zimbabwe. In total,
Africa accounts for nearly 50% of the world’s diamond production.
The diamonds occur in kimberlite pipes and dikes and in associated alluvial placers. The largest pipe in
is the 133 acre (54 hectare) Premier. The Premier Mine has been the source of some of the world's largest diamonds including the Cullinan, Premier Rose, Niarchos, Centenary and Golden Jubilee. The largest diamond ever found, the fist-size (3,106 carats) Cullinan, was recovered from the Premier. South Africa
The Finsch mine covers an area of 44 acres (17.9 ha) and lies 92 miles (160 km) northwest of
. It is one of DeBeers’ seven South African operations. Discovered in 1961, the deposit was initially developed by open pit. Since 1991, underground mine operations continued beneath the abandoned pit. Production from the mine in 2001 was 2.46 million carats from 4.8 million tonnes of ore (51.7 ct/100 tonnes). Kimberley
Diamond-bearing gravels were discovered as early as 1903 close to the
, 20 miles (35 km) northeast of the present location of the Limpopo River Venetia mine in . In 1969, De Beers launched a reconnaissance sampling program to locate the source of the alluvial deposits, and kimberlite pipes were discovered upstream in 1980. Mine construction began in 1990, and the South Africa Venetia mine opened in 1992 with full production in 1993. This mine represents one of De Beers’ single largest investments in . Situated 50 miles (80 km) from South Africa in the Messina , the property required a capital investment of $400 million. The mine produced 4.98 million carats from 4.6 million tonnes of ore in 2001 (108 cts/100 tonnes). Northern Province
There are 12 kimberlites in the
Venetia cluster. Of the 11 pipes and one dike, only two kimberlites, K1 and K2, are currently being mined. Some of the pipes were formed by multiple intrusive events resulting in a variety of kimberlite facies. The kimberlites are clustered over approximately 2 miles (3 km), while the total surface area of kimberlite is 69 acres (28 ha). Venetia is being mined by conventional open-pit. Surface mining is expected to continue for 20 years. The current targeted pit depth is 1,280 feet (400 m).
The diamonds were found in gravel buried by Tertiary basalt in an active tectonic environment similar to that of the Urals in Russia, the West Coast of the United States, and in some Archean greenstone terrains in Canada (Erlich and Hausel, 2002; Ayer and Wyman, 2003; Kaminsky and others, 2003). It is thought that the diamonds were derived from phreatomagmatic volcaniclastics and tuffs associated with lamprophyre pipes (Atkinson and Smith 1995). Diamonds in such geological terrains provide signatures suggesting derivation from a relatively shallow mantle (<80 km) (Ayer and Wyman, 2003).
. Decades after the diamond discoveries in NSW, Ashton Exploration discovered diamonds near Northern Territories , Mt. Percy West Kimberley by following a trail of kimberlitic indicator minerals in 1976. The mineral trail led to diamondiferous lamproite in the Ellendale field (Tertiary). In August 1979, diamonds were found in Smoke Creek, more than 350 km to the northeast. In October 1979, the Argyle lamproite (1.2 Ga) was discovered (Atkinson and Smith, 1995). Both lamproite fields are located within Proterozoic mobile belts cratonized around 1.8 Ga and were tectonically active until the Devonian or later (Jaques et al. 1982, 1983; Atkinson and others, 1984). Presently, about 450 lamproites, kimberlites and lamprophyres have been identified in of which more than 180 are diamondiferous. Some of the recently discovered kimberlites yielded minor to significant diamond grades (Berryman and others, 1999). Australia
’s total diamond production in 2001 was 26.2 million carats, a decrease of 0.4 million carats from the previous year. The Argyle mine (26.1 million carats) accounted for nearly all of the Australian production. The Merlin mine in the Australia produced 55,000 carats making it the second largest Australian producer in 2001. Northern Territory
reserves at the Ekati mine are substantial. On Ore June 30th, 2003, the Ekati mine reported 47.7 million tonnes of ore reserves graded at 0.8 carat/tonne (36.6 million carats of recoverable diamonds) based on a 2 mm cutoff size. Measured, indicated, and inferred kimberlite resources stood at 127.9 million tonnes of ore containing an estimated 171.2 million carats (Robertson, 2004)! As exploration continues on the property, these reserves will increase.
Production began in the mid-1980s at the Argyle mine resulting in
becoming a leading diamond producer. At full production, the mine yielded more than 30% of the world’s annual production. Further development of the open pit continued into 2001, and the current operator (Rio Tinto) reported plans to expand operations underground. Australia
Diamonds were recovered from the
placer mine in the lower reaches of Limestone Creek, 12 miles (20 km) northeast of the Argyle. This deposit was discovered in the early 1980's and mined by Poseidon/Freeport and Normandy Bow River from 1988 until late 1995 (Biggs and Garlick, 1987). The plant was inactive at the end of late 1995, after nearly 7 million carats were produced from 24 million tonnes of gravel. Normandy
Kimberley Diamond Company acquired the Ellendale leases previously held by Argyle Diamond Mines. Initial bulk sampling results from Ellendale 4 and 9 revealed higher ore grades near the surface. The company reported the Ellendale 4 resource at more than 2 million carats to a depth of 450 feet (140 m) (23 million tonnes at 0.088 carat/tonne), which included a higher-grade zone (444,000 tonnes at 0.261 carats/tonne) to a depth of 9.6 feet (3 m). The near-surface enrichment zone was part of the mining target for 2002. Primary diamond resources of Ellendale 4 and 9 were estimated at more than 2.6 million carats.
For the first three years of operation, 2.2 million tonnes of ore is expected to be mined from the top 9.6 feet (3 m) of enriched material on both Ellendale 4 and 9. The ore is estimated to average 0.15 carats/tonne. The company also reported the discovery of 11 previously unknown lamproite pipes in the area (Shigley and others, 2001; MiningNews.net,
January 10, 2002).
The Merlin mine, which was developed on a group of 12 diamondiferous kimberlites in northern
, yielded the country’s largest diamond, the 104.73-carat Jungiila Bunajina (“star meteorite dreaming stone”) white diamond. Merlin is located 50 miles (80 km) south of Borroloola. After 6 years, it was announced that the mine would close at the end of the 2002 due to marginal ore. Australia
A diamond rush occurred in
in 1725, and by the end of 1729 several diamond placers had been found in eastern Brazil in the region of Brazil Diamantina (“diamond city”). Placers were also found along the Sao Francisco, , Goyas, and other streams in southeastern Parana . In 1844, rich diamond placers were found in another region of Brazil —the state of Brazil Bahia to the north. During the first 120 years of mining, about 10 million carats were recovered, including some weighing more than 100 carats.
The primary source of the diamonds has not been found, and it was initially assumed that a rock referred to as itacolumite (micaceous sandstone) was the source. This assumption was based on the presence of middle Proterozoic diamondiferous conglomerates that have supported some small mining operations in the
The large number of diamonds found in placers suggests that major primary diamond deposits will be found in
some day. Since 1967, a systematic exploration program identified more than 300 kimberlite, lamproite, kamafugite, and melilitite intrusives, none of which contain economic amounts of diamond (Bizzi et al. 1994; Meyer et al. 1994). A total of about 55 million carats have been recovered from Brazil with annual production averaging about 1.2 million carats. Brazil
Diamond deposits in the Liaoning Province of China are associated with kimberlite. More than 100 kimberlites are found in this region including the Jingangshi kimberlite, which contains commercial amounts of diamond (Sunagawa, 1990). At another locality, the Changma mine in the
near Mengyin, about 500 km southeast of Shandong Province , is Beijing ’s largest diamond producer. This deposit was initially mined as open pit over the past several decades and converted to underground mining in 2002 with an expected life of another 30 years. The Changma deposit consists of a couple of kimberlite diatremes and a dike that all merge at 40 m below the surface. The kimberlite has been drilled to depths of 600 m. Production from the mine during the past 30 years included 1.6 million carats recovered from ore that averaged 1.27 carats/tonne: the largest diamond was a 119 carat stone. The property has an indicated resource of 1.4 million tonnes of ore at a grade of 0.92 carat/tonne with an inferred resource of 1.5 million tonnes of 0.63 carat/tonne. The Changma property includes 9 diamondiferous kimberlites with a total measured and indicated resource of 9.7 million tonnes at an average grade of 0.055 carat/tonne (Beales, 2004). China
The majority of the diamonds was found in placer deposits (Sakuntala and Brahman 1984), although diamonds were also found in the Majhagawan lamproite as early as 1827. After kimberlite was described in
Mitchell and Bergman (1991) indicate there are several other lamproites, kimberlites, and peridotites in this region, and Rock and others (1992) also report several olivine lamprophyres and minettes of potential economic interest occur in eastern
. Known kimberlites in India are primarily Proterozoic in age and include diamondiferous kimberlites in the Wajrakarur field in the Andra Pradesh of the southern kimberlite province and kimberlites in the India field in southeastern Madhya Pradesh in the central province (Middlemost and Paul 1984). Raipur
Many of the Indian deposits were depleted by the 19th century and new deposits were discovered in the mid 20th century, including placers in the Junkel region and
, and in the Simla region near the Koel Valley Himalayas (which were originally described in Sanskrit texts). Total historical production is estimated to be between 14 to 21 million carats. Currently, about 20,000 carats are produced each year.
There is little doubt that
, which has become a major diamond producer, will remain in the forefront of diamond production and exploration for decades to come. Recent exploration in Canada has resulted in the discovery of more than 500 kimberlites (including some unconventional host rocks) of which nearly half are diamondiferous (Kjarsgaard and Levinson, 2002). Some of the unconventional host rocks include lamprophyre (including minette) and actinolite schist at Canada , that is interpreted to represent metamorphosed komatiite. Wawa, Canada
The North American Craton is the largest craton in the world. The Cratonic basement rocks of
continue south into the Canada and underlie large regions of Montana-Wyoming and the US Great Lakes region. However, exploration in the has been relatively minimal. Even so, more than 100 kimberlites, lamproites, and lamprophyres have been identified in the southern extension of the North American craton in Colorado, Wyoming and Montana. Approximately half of the kimberlites found in US and Colorado are diamondiferous, only one in Wyoming has yielded diamonds to date. The presence of several hundred kimberlitic indicator mineral anomalies, several diamonds, along with some geophysical and remote sensing anomalies support that the Wyoming Craton has been intruded by a major swarm of kimberlitic and related intrusives, most of which remain undiscovered. In that a large part of the Montana craton remains unexplored for diamonds, additional discoveries are expected. In the Wyoming Great Lakes region, a group of about 30 kimberlites are reported in the Michigan-Illinois area (8 of which contain trace amounts of diamond) (Hausel, 1998).
One of the great exploration success stories of the 20th century was the discovery of diamonds in the Northwest Territories of Canada, which sparked the largest claim staking rush in history (Krajick, 2000). A group of diamondiferous kimberlites were found nearly 300 km northeast of
under a group of shallow lakes in the Lac de Gras region. Within a few years following the discovery, Yellowknife ’s first diamond mine was commissioned by BHP in late 1998 (Figure 9). This mine, known as Ekaki, is a world class mine. The mine property includes a group of 121 kimberlite intrusives, and to date, commercial mineralization has been identified and reserves established for the Fox, Leslie, Misery, Koala, Koala North, Panda, Beartooth, Sable and Pigeon kimberlites on the Ekati property: the other kimberlites are being evaluated for reserves. The mine is anticipated to have a minimum life of at least 25 years. Canada
In 2001, Ekati produced 3.7 million carats totaling about 6% of the world’s diamond value. In 2003, production increased to 6.96 million carats (EMJ, 2004). The open pit operation on the Panda kimberlite reached its maximum economic depth in 2003, five years after mining was initiated. However, the declining production from the Panda open pit was replaced by production from the nearby Misery and Koala open pits. Evaluation showed that the Panda kimberlite mine life could be extended using underground mining techniques, thus the remaining kimberlite is being developed using sublevel retreat mining. Underground mining was previously initiated at the adjacent Koala North pipe in 2002. The Panda underground mine is expected to produce 4.7 million carats over an operating period of 6 years, with production scheduled to begin in 2005, followed by full production in 2006. The Ekati production for the first quarter of 2004 totaled 1.27 million carats of diamonds, which was a 40% decline from the previous quarter. For the first 9 months of fiscal year 2004, the Ekati mine produced more than 5.3 million carats.
A few other commercial properties have been identified in the
. In addition, numerous other properties being explored or evaluated for reserves. These include Northwest Territories , Diavik and Snap Lake . Production at the Diavik mine began in 2003. The Diavik pipes located in the Lac de Gras region east of Ekati, are being mined by Diavik Diamond Mines based out of Jericho (Figure 9). Diavik Diamond Mines is a subsidiary of London-based Rio Tinto, and the mine is a joint venture between Rio Tinto (60%) and Toronto-based Aber Diamond Mines (40%). Rio Tinto assumed operating responsibility from their subsidiary, Kennecott Canada Exploration. The mine is estimated to contain 138 million carats of diamond and includes four kimberlites (A154S, A154N, A418, A21). The A154S kimberlite is one of the richest kimberlites in the world and contains a reserve of 11.7 million carats at an average grade of 5.2 carats/tonne. The property is anticipated to yield 6 to 8 million carats/year when in full production and has reserves that will sustain the operation for 16 to 22 years. The property lies on a 20 km2 island known as Yellowknife , 300 km northeast of East Island . The Diavik kimberlites (55 Ma) intruded the Precambrian basement complex (2.5 – 2.7 Ga). Yellowknife
mine is located in a kimberlite dike about 100 km south-southeast of Ekati and 220 km northeast of Snap Lake . Yellowknife will be DeBeers’ first mine developed outside of southern Snap Lake Africa and is anticipated to begin production in 2006, or possibly as late as 2008. The kimberlite will be mined entirely underground. The kimberlite is estimated to host 38.8 million carats with an average ore grade of 1.46 carat/tonne.
Toronto-based Tahera Diamond Corporation is the operator of the
project located about 150 km north of Ekati near Jericho ’s Lupin Gold mine. This property includes six diamondiferous kimberlites within the Echo Bay located 170 km north of Ekati. When placed into production, the property would produce about 6 million carats over a mine life of 8 years. Reserves of 2.6 million tonnes of ore averaging 1.2 carats/tonnne have been established. The mine is expected to begin development in 2004 and production scheduled for 2005 (EMJ, 2004). Nunavut Territory
Another project of DeBeers
- the Victor Project, lies in the James Bay Lowlands of northern Canada , approximately 90-km west of the coastal community of Ontario Attawapiskat. De Beers anticipates a decision regarding mine development in mid-2004. Victor is one of 18 kimberlite pipes discovered on the property, 16 of which are diamondiferous. The Victor kimberlite has a surface area of 15 hectares and consists of two pipes that coalesce at the surface known as the Victor Main pipe and Victor Southwest pipe. The Victor kimberlite is a complex pipe consisting of pyroclastic crater and hypabyssal facies kimberlite and has highly variable diamond grades. If a decision is made to put the property in production, the open pit mine will have a life of 12 years and total project life of 17 years. The mine will be supported by a processing plant designed to process 2.5 million tonnes per year.
DeBeers is also involved in the Kennady (Gahcho Kue)
Lake project located about 100 km east of near Snap Lake and southeast of Ekati. Ft. Defiance is currently under exploration by a joint venture between Mountain Lake Resources and DeBeers. The property includes the 5034, Hearne, and Tuzo kimberlites. Initial sampling of the 5034 and Hearne pipes yielded an average ore grade of 1.67 carats/tonne. If this project receives a go-ahead, it is expected that permitting will require 2-3 years followed by another 3 years of mine development (EMJ, 2004). Kennady Lake
Many other deposits have been found in
since the 1990s in the Canada , Northwest Territories , Nunavut , Alberta , and Ontario, Quebec (Olson, 2001). Saskatchewan
According to EMJ (2004),
is currently supplying about 15% of the world’s diamonds and is expected to show dramatic increases in the future. In 2002, the Canadian diamond industry produced nearly 5 million carats. In 2003, production increased to 11.2 million carats, and it is estimated that essentially 50% of the world diamond exploration funding is focused on Canada . Canada
The Udachnaya pipe was found in 1955 and mining began on the associated placers in 1957, followed by open pit operations in the pipe. Udachnaya has been the most productive diamond mine in
with more than 14.4 million carats mined of which 80% were gems. By 1956, over 500 kimberlites had been discovered in the Russia . During the next 30 years, USSR became the third largest producer in the world: nearly all its production came from mines within the northern Siberian platform. Russia
In 1960, the Aikhal pipe was discovered in Yakutiya: mining began in 1962 and ceased sometime between 1981 and 1988, presumably due to overproduction from other sources. Production resumed after 1988, and by 1995 the pit reached a final depth of 770 feet (240 m). Annual production at the peak of mining was 600,000 carats at an average grade of 1.0 carat/tonne (Yakutalmaz 1999).
Another commercial pipe, known as the Sytykanskaya was discovered in 1955. Open pit mining began in 1979, and 600,000 carats/year were produced (average grade of 0.60 carat/tonne). The mine was scheduled to close in 2001 (Yakutalmaz 1999). Another commercial diamond mine, the Internatsional’naya pipe, was found in 1969. Mining began in 1971 and the open pit was developed to a depth of 900 feet (280 m) by 1980. Open pit operations ceased but plans were made to resume mining underground.
The 23rd Party Congress pipe was discovered in 1959: mining began in 1966 on this very rich pipe. The ore averaged 6.0 carats/tonne and the open pit reached a depth of 395 feet (124 m) after 15 years of operation. The Jubilee (Yubileinaya) pipe was discovered in 1975. Following the removal of 225 to 320-ft (70–100-m) of basalt overburden, open pit mining began: the Jubilee was anticipated to replace production from the declining Udachnaya pipe.
During the 1970s, other diamondiferous kimberlites were discovered within the Russian platform. At about the same time, several kimberlitic pipes were discovered northeast of the city of
, which included the Lomonosov diamond deposit. Currently, Arkhangel’sk is the 4th largest producer of diamonds in the world (by weight). The Russia of Natural History reported that the country has produced a total of 332 million carats and currently has an annual production of 10 to 12.5 million carats. American Museum
In 1890 and 1901, secondary placer deposits were discovered in
and Venezuela , and near the end of the 1960s, a placer deposit was found on Guyana in southeastern Caroni River . To mid-1969, 1.3 million carats had been mined; the largest stone weighed 12 carats. In September 1971, near the town of Venezuela in the state of Bolivar, another significant placer was discovered. Within a short period, monthly diamond production from the Salvacion region reached 50,000 carats but the source of the diamonds remains unknown. Salvacion
Several diamondiferous pipes have been reported in other cratons such as in the
Greenland region, and also in Kazakstan. Kazakstan also has the added attraction of having some very unusual and very rich unconventional metamorphic diamond deposits – but most of the diamonds are low-value industrial stones (Erlich and Hausel, 2002).