Rio Tinto's diamond production for the year fell by 15% to 18.4 million carats from 21.6 million carats in 2017, as production at the Argyle mine in 2018 fell by 18% compared to 2017, when production was enhanced by the processing of higher grade alluvial tailings. The fourth quarter in particular put a drag on the annual figures, as the 3.2 million carats unearthed represented a 48% decline from Q4 2017 - albeit against a high base of 7.21 million carats - and a 16% decline from last quarter. The trend of a gradual decline in output does not look to change any time soon, as the diversified miner announced production guidance for 2019 at between 15 and 17 million carats.
At the Diavik Diamond Mine in Canada's remote Northwest Territories that Rio Tinto operates and owns a 60 percent share (Dominion Diamond Mines 40%), the 4.36 million carats recovered in 2018 were 3% fewer than 2017, as lower recovered grades were partially offset by higher ore processing. At 1.1 million carats, Q4 output at Diavik increased by 2% over the same quarter in 2017 and 1% over last quarter. The A21 project successfully mined first ore in March 2018 and reached commercial production during the fourth quarter. The A21 project successfully mined its first ore in March 2018 and reached commercial production during the fourth quarter.