Argyle diamond mine

Description and Location

• The Argyle diamond mine covered about 50ha (124 acres) in a linear shape and reached a depth of 600m (1,970ft) at its deepest point.
• The mine originally used open-pit techniques and transitioned to underground block cave mining in 2013.
• The mine site is owned by the Rio Tinto Group.
• The Argyle diamond mine is located in the Kimberley region in Western Australia, southwest of Lake Argyle in the Matsu Ranges.
• The mine is approximately 550km (340mi) southwest of Darwin and 185km (115mi) away from the nearest settlement, Kununurra.
• A residential camp was constructed on site for the workers.

History and Geology

• Alluvial diamonds were discovered in the West Kimberley region in 1969, and the source was traced to the headwaters of Smoke Creek.
• The Argyle pipe, AK-1, was discovered in 1979, and mining operations commenced in 1985.
• The Argyle mine is a volcanic pipe composed of olivine lamproite, formed through explosive eruption in a zone of weakness in the continental crust.
• Diamonds were found within the intact core of the volcanic pipe, predominantly eclogitic.
• Semi-permanent streams have eroded portions of the pipe, creating significant alluvial deposits of diamonds.

Production and Diamond Characteristics

• The Argyle mine was the fourth-largest diamond-producing mine in the world by volume, with annual production averaging 8 million carats (1,600kg).
• Production peaked in 1994 with 42 million carats (8,400kg) produced, and most of the gem-quality production was in brown diamonds.
• Argyle diamonds come in various colors, including pink, yellow, white, grey, and green.
• Pink and red diamonds are rare, with Argyle being the main source, producing 90 to 95% of them globally.
• Argyle diamonds are classified as type 1a and have low levels of nitrogen impurities.
• Common inclusions in Argyle diamonds include unconverted graphite, orange garnet, pyroxene, and olivine.

Annual Diamond Tender and Reserves

• Since 1984, Argyle has held the exclusive invitation-only Argyle Pink Diamond Tender, offering one carat of polished diamond for every one million carats of rough pink diamonds produced.
• In 2009, Argyle introduced rare blue diamonds in their Once in a Blue Moon collection.
• The Argyle mine had initial proven reserves of 61 million tonnes of ore, containing about 400 million carats of diamonds, with additional estimated reserves of 14 million tonnes of ore and 85 million carats of diamonds.
• As of 2001, the open-pit-mined area contained 220 million tonnes of ore with grades of 2.5 to 3.0 carats per tonne.
• Alluvial deposits of diamonds are believed to have been exhausted.

Economics and Underground Expansion

• The Argyle diamond mine was economically feasible due to its large reserves and high-grade ore.
• The estimated value of Argyle diamond production was only US$7 per carat.
• Rio Tinto received approval for a future expansion project to transition from an open pit to an underground mine in 2005.
• The underground mine increased annual production to 9 million tonnes of ore, but the high costs of deeper mining outweighed the diamond yield.
• The Block Cave, using advanced mining technology, operated until the end of 2020.

Argyle diamond mine Data Sources