Perth: Rio Tinto reported diamond production surged 50 percent year on year to 4.3 million carats in the fourth quarter that ended December 31 as output from the Argyle mine in Australia almost doubled.

The Argyle pit in the remote East Kimberley region of Western Australia produced 3.4 million carats in the three months, an 86-percent jump from a year ago, according to a statement January 19. Production at the miner’s Diavik mine in Canada slipped 3 percent to 899,000 carats.

The mining giant owns the Argyle mine outright and holds a 60-percent share in Diavik in a joint venture with Dominion Diamond Corporation.

Rio Tinto’s full-year production for 2015 grew 25 percent to 17.4 million carats, below its guidance of 18 million carats issued on October 16. Production in the fourth quarter was 4 percent lower than in the previous three-month period because of process-plant pauses to manage inventory levels. The annual output from Argyle, however, still jumped 47 percent to 13.5 million carats in 2015.

Full-year output from Diavik fell 11 percent to 3.8 million carats because of process-plant pauses in the fourth quarter and the absence of stockpiled ore that had been processed in the first half of 2014. The miner recovered 3 percent fewer carats in the final quarter compared with the same period the previous year because of lower processing volumes largely offset by higher recovered grades.

The full-year company-wide figure includes 77,000 carats produced from the Murowa Diamonds mine up until June 2015, when Rio Tinto sold its 78-percent stake in the Zimbabwe mine.