Rio Tinto today released its interim results for the first six months of 2015 reporting a 23% decline in gross revenue for its diamonds business. Gross revenue from its interests in Argyle, Diavik and Murowa (which it sold at the end of June) dropped to $ 331 mn from $ 431 mn a year earlier, the company said.

It added that it diamond business saw a small drop in EBITDA for the first half of 2015 from $ 156 mn last year to $ 144 mn this year, while net earnings rose from $18 mn to $ 31 mn during the same periods.

As earlier reported, production during the first half of the year was up 18% with higher volumes at Argyle from the continued ramp up of production from the underground mine offsetting lower carats recovered at Diavik, reflecting lower ore availability as mining progressed through an area of higher dilution in the first quarter and the absence of stockpiled ore which was processed in 2014 first half. On June 26, Rio Tinto announced the sale of its interest in the Murowa diamond mine in Zimbabwe.

Rio Tinto also announced that the Argyle underground mine development was completed in June and the operation will continue to ramp up production through 2015. It added that the development of the A21 pipe at Diavik is advancing as planned, with first production still expected in 2018.

The miner reported that across all commodities it had registered a 43% decline in net earnings from $ 5.12 bn in the first half of 2014 to $ 2.9 in the first half of 2015. Rio Tinto chief executive Sam Walsh said “This is a robust set of results, given the tough operating environment.”