Harare: Rio Tinto said its 78 percent owned Murowa mine in Zimbabwe recorded a 4 percent drop in output to 101,000 carats during the fourth quarter of 2014.

The company, which also has operations in Australia and Canada said its total rough diamond output declined 37 percent year on year to 2.841 million carats during the same period under consideration.

The decline was attributed to a maintenance shutdown and the transition from open pit to underground mining at its Argyle mine in Australia, and a shift toward processing lower grade ore at its Diavik mine in Canada.

Argyle’s output declined 43 percent to 1.813 million carats during the quarter while that of Diavik (60 percent-owned by Rio) eased 25 percent to 927,000 carats.

Meanwhile, Rio said its annual rough diamond production dropped 14 percent to 13.872 million carats, due to the decline in production at Argyle caused by the transition to underground mining.

Argyle mine output dropped 19 percent to 9.188 million carats last year as well while Diavik’s production was unchanged at 4.34 million carats. However, Murowa output leaped 7 percent to 344,000 carats in 2014.