Rio Tinto reports rough diamond output at its Argyle Mine in Australia topped 3.5 million carats in Q1 2018, representing an 18% increase over output in the first quarter of last year, but a massive 42% decline compared to the 6.1 million carats recovered in Q4 2017. The mining giant attributes the increase over Q1 2017 to relatively fewer weather disruptions and the additional processing of higher grade alluvial tailings.
Production at the Diavik Mine in Canada's NWT, in which Rio Tinto holds a 60% stake, carats recovered in the first quarter of 2018 were 6% lower than the corresponding period in 2017 due to lower recovered grades and increased by a mere 0.5% compared to Q4 2017. Development of the A21 project is ahead of schedule with first ore uncovered in March and the mine is expected to be at full production capacity during the fourth quarter of 2018.
Overall output during the first quarter climbed 11% compared to the same period last year, delivering 4.6 million carats compared to 4.15 million carats in Q1 2017, although output fell by 36% relative to the previous quarter. Diamond production guidance for 2018 is between 17 and 20 million carats, representing a slight decline from the 21.63 million carats produced in 2017, and within the same range as the 17.95 million carats mined in 2016. In Rio Tinto's 2017 annual report, the company announced significant changes in estimates of Ore Reserves and Mineral Resources at Rio Tinto's Argyle Diamond mine, as the estimated Argyle Ore Reserves decreased by 13Mt from 29Mt to 16Mt. The remaining reserves underpin the operation until 2020, with opportunities to increase reserve estimates and extend the operational life subject to technical and financial performance.