Rio Tinto’s diamond production rose 47 percent year on year to 4.135 million carats in the second quarter of 2013. Growth was driven by higher grades and a rise in ore processed at its fully-owned Argyle mine in Western Australia, where underground mining was commissioned in April 2013.

Production at Argyle jumped 87 percent to 3.13 million carats during the quarter as the amount of ore processed increased 16 percent to 1.929 million tonnes.

Rio Tinto’s production at the Canada-based Diavik mine, in which it owns a 60 percent stake, fell 13 percent to 936,000 carats due to lower grades of ore mined during the quarter. The company reported that it completed transition to underground mining at Diavik in June and that production at all three kimberlite pipes is now underway.

Rio Tinto also owns 78 percent of the Murowa mine in Zimbabwe where its share of production grew 21 percent to 69,000 carats.

During the first half of the year, Rio Tinto’s total production rose 20 percent to 7.37 million carats with Argyle production up 28 percent to 5.12 million carats. Production at Diavik increased 3 percent to 2.103 million carats during the six months, and the company’s share of Murowa production rose 20 percent to 147,000 carats.

The company expects to recover 15.7 million carats of diamonds in 2013 compared to 13.122 million carats mined last year. In June, Rio Tinto announced its decision to retain ownership of its diamond business following an 11 month review of the unit.