Production Argyle diamond mine

1 production

1.1 diamond characteristics

1.1.1 annual diamond tender


1.2 reserves
1.3 economics
1.4 underground expansion

production

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argyle fourth-largest diamond producing mine in world volume, averaging annual production of 8 million carats (1,600 kg). production peaked in 1994, when 42 million carats (8,400 kg) produced. since operations began in 1983, argyle s open pit mine has produced on 750,000,000 carats (150,000 kg) of rough diamonds.

most of argyle s gem-quality production in brown diamonds. these diamonds difficult sell, although rio tinto has seen success in decade-long marketing campaign promote brown diamonds champagne , cognac toned. in contrast, company has no problems selling diamonds in pink, purple, , red tones, rare , in high demand, therefore commanding premium prices. pink diamonds processed , sold polished diamonds specialised team based in perth customers worldwide.

the mine has ore processing , diamond sorting facilities on site. once diamonds removed ore , acid washed, sorted , shipped perth further sorting , sale. significant quantity of diamonds cut in india, low costs of labour allow small diamonds cut profit; relevant argyle mine, on average produces smaller rough diamonds other mines do.

diamond characteristics

a large brown argyle diamond, 3.6 carats

the diamonds produced @ argyle diamond mine of average low quality. 5% of mined diamonds of gem quality, compared worldwide average of 20% (author janine roberts contends near-gem quality rating subjective , misleading because these diamonds can cut gems if desired.); of remaining 95%, evenly split between classifications of near gem quality , industrial grade; 80% of argyle diamonds brown, followed 16% yellow, 2% white, 2% grey, , less 1% pink , green. despite low production volume of pink , red diamonds, argyle mine reliable source in world, producing 90 95% of pink , red diamonds. argyle diamonds classified type 1a (see material properties of diamond), , have low levels of nitrogen impurities, colour resulting instead structural defects of crystal lattice. argyle diamonds tend fluoresce blue or dull green under ultraviolet light, , blue-white under x-ray radiation. common inclusion unconverted graphite, followed crystalline inclusions of orange garnet, pyroxene, , olivine.

annual diamond tender

each year, small collection of best pink diamonds offered in exclusive sale known argyle pink diamond tender. every 1,000,000 carats (200 kg) of rough pink diamonds produced mine, 1 carat (0.20 g) polished offered sale @ tender. invitation-only event. access collector s edition catalogue , website access in highly sought after.

in march 2009, argyle announced first ever tender of rare blue diamonds. once in blue moon collection sourced on several years, , comprised range of precious blue , violet diamonds, weighed in total 287 carats (57.4 g).

in 2016, annual argyle tender became highest selling tender in 20-year history, according diamond investment & intelligence center.

reserves

initial proven reserves of argyle mine 61 million tonnes of ore, average ore grade of 6.8 carats (1.36 g) per ore tonne, 400 million carats (80,000 kg). further estimated reserves of 14 million tonnes of ore, @ grade of 6.1 carats (1.22 g) per tonne (85 million carats, 17,000 kg), existed. of 2001, reserves , resources in open-pit mined area contain 220 million tonnes of 2.5 3.0 carat (500 600 mg) per tonne graded ore, sufficient sustain current production rates until 2007. ore grades @ argyle mine unusually high, commercial diamond mines averaging grades of 0.3 1.0 carats (60 200 mg) per metric ton. alluvial deposits of diamonds believed have been exhausted.

in 1995, drilling samples taken 300 m below floor of pit indicated possible presence of 100 million tons of ore, estimated grade of 3.7 carats (740 mg) per ton. in mid-1990s, part of west wall of open pit mine, containing 25 million tonnes of waste rock, began collapse. in 1998, decision made remove or cut unstable part of west wall freed further economic ore in south part of open pit.

an exploration decline constructed @ cost of a$70 million evaluate economics of mining diamonds diamoniferous pipes below floor of open pit; these reserves mined underground (by block caving), rather open pit method used. in late 2005, rio tinto ltd concluded operation economically feasible. pre-production construction of underground mine commenced in mid 2006

economics

the argyle diamond mine economically feasible because large reserves , high-grade ore offset low average diamond value. estimated value of argyle diamond production us$7 per carat ($35/g); compares values of $70 per carat ($350/g) diamonds produced @ diavik mine , us$170 per carat ($850/g) @ ekati mine, both in canada.[1] however, argyle has 2 4 times concentration of diamonds (ore grade) of these mines. makes extraction economically feasible, mine costs related amount of ore processed, not amount of diamond extracted.

underground expansion

aerial view of open pit in 2007

in 2005, rio tinto given go-ahead future expansion project, moving open pit underground mine. plan postponed; in september 2010 rio tinto announced fresh plans develop underground mine beneath existing pit, increasing annual production 9 million tonnes of ore.

the project predominantly underground construction requiring high-quality development , engineering excellence. block cave expected operate until 2018 using latest in mining technology, including sandvik s auto mining technology. project due completed 2013, 2 years later first planned, after diamond prices slumped.