Australia's 865 Million Carat Argyle Mine: 90% of Earth's Pink Diamonds, Then It Ran Out

#Geology #Australia #PinkDiamonds Under a red gap in the Kimberley ranges of Western Australia sat the biggest diamond mine in history — by volume. Argyle, catalogued as AK1, ran from 1983 to 2020 and produced more than 865 million carats of rough, about a third of the world's diamonds by stone count. It was also one of the cheapest sources on Earth: roughly 80% of its output was brown, only about 5% was gem quality, and its rough averaged near US$7 a carat in Argyle's day against about US$70 at Canada's Diavik. Hidden in that brown flood — about one polished carat per million carats of rough — was more than 90% of the world's pink diamonds. On 3 November 2020 Argyle mined its last ore. Prices never turned against it. The orebody simply ended. This documentary follows the whole story: seven years of helicopter creek sampling across some 55,000 square kilometres of the Kimberley by the Ashton Joint Venture, nicknamed Ashton's Flying Circus; the sample taken on 2 October 1979 by geologist Maureen Muggeridge of CRA Exploration, and the trail up Smoke Creek to gravels running as high as 15 carats per cubic metre, the richest diamond gravel on record anywhere; and the pit that followed, grading 2.5 to 3 carats per tonne where an ordinary diamond mine runs a third of a carat to one. Then the geology that broke the rulebook. The K in AK1 stood for kimberlite; the rock is olivine lamproite, making Argyle the first economic diamond deposit ever found in a non-kimberlite host, sitting on the battered edge of a craton rather than its stable core. We also separate the three ages that get endlessly confused: collision at roughly 1.91 to 1.80 billion years, diamond growth near 1.58 billion, and an eruption long put at 1.2 billion but re-dated in 2023 to about 1.31 to 1.26 billion, tied to the breakup of the supercontinent Nuna. And the colour: per the GIA, about 99.5% of pink diamonds are pink from no impurity at all, but from physical deformation of the crystal lattice — a defect still unidentified. Key facts: East Kimberley, Western Australia, about 110 km south of Kununurra in a straight line. Alluvial mining from 1983, open pit from 1985, block-cave underground from 2013. First reserve 61 million tonnes at 6.8 carats per tonne; 5.1 million at 1.9 by end of 2019. 38 annual tenders: 33 stones in Antwerp in 1984, a final 70 stones and 81.63 carats in 2021. Barramundi Gap is a sacred site of the Miriwoong and Gija peoples; closure leaves a pit lake in perpetuity. Studies & sources used: Olierook et al. (2023), Nature Communications — dating the Argyle eruption to the breakup of Nuna: https://www.nature.com/articles/s4146... Richardson (1986), Nature — latter-day origin of diamonds of eclogitic paragenesis: https://www.nature.com/articles/322623a0 Geoscience Australia — Australian Mineral Facts: Diamond: https://www.ga.gov.au/education/miner... GIA Gems & Gemology, Winter 2018 — natural-colour pink, purple, red and brown diamonds: https://www.gia.edu/gems-gemology/win... GIA Research — why pink diamonds are pink: https://www.gia.edu/gia-news-research... Society of Economic Geologists — the discovery of the Argyle pipe: https://pubs.geoscienceworld.org/segw... Rio Tinto — Argyle operations and closure: https://www.riotinto.com/en/operation... Australian Human Rights Commission — Native Title Report 2006, Ch.5, the Argyle Participation Agreement: https://humanrights.gov.au/our-work/p... Australian Centre for Geomechanics, UWA — Argyle closure, a First Nations perspective: https://papers.acg.uwa.edu.au/d/2515_... PorterGeo — Argyle alluvial diamonds, Smoke Creek and Bow River: https://portergeo.com.au/database/min... Chapters: 00:00 The Gap in the Kimberley 03:30 Ashton's Flying Circus 05:40 The Sample That Found It 07:00 The Richest Diamond Gravel on Record 11:30 AK1: The K Stood for the Wrong Rock 16:00 Brown, Cheap and Unwanted 19:00 Barramundi Gap and the Traditional Owners 22:30 Why Pink Diamonds Are Pink 25:00 Three Ages and the 2023 Re-Dating 28:00 The Tender and the Named Stones 31:00 The Pit Lake and What Replaces Argyle Keywords: Argyle diamond mine, Argyle pink diamonds, AK1 lamproite pipe, East Kimberley geology, pink diamond tender, Clifford's rule, geology documentary. If you love deep-time geology and the forces that shaped Australia, subscribe for more documentaries on the ancient rocks, mines and landscapes of the continent.