Petra Diamonds reported fiscal year revenue rose 44 percent year on year to $316.9 million for the 12 months that ended on June 30. However, the mining company reported a loss of $2.1 million compared with profit of $59.2 million one year ago in part because mining and processing costs surged 52 percent to $222.6 million and Petra recorded a foreign exchange loss of $38.6 million.

Rough diamond production rose 98 percent year on year to 2.2 million carats. Petra Diamonds confirmed that its expansion plans remained on target to increase its production to 5 million carats by year 2019.

Johan Dippenaar, Petra's chief executive, said the company consolidated its position as London’s largest listed diamond mining group during the year. ''The successful acquisition and integration of Finsch, the step up from AIM to the Main Market of the London Stock Exchange, and the delivery on production targets all demonstrate Petra’s progression to the next stage of its development.''

He added that the rough diamond market continues to experience volatility and it is expected to remain under pressure for the short-term due to the prevailing climate of economic uncertainty. But the long-term outlook for the supply and demand balance in the rough diamond industry is considered to be robust.

Petra Diamonds held its first rough tender of the new fiscal year earlier this month and achieved revenue of $50.9 million for 318,687 carats. Rough diamond prices from the company's Finsch and Cullinan mines were in line with fiscal guidance at $133 per carat and $149 per carat respectively, but rough diamonds from Koffiefontein achieved $566 per carat at the tender, which was far above the $475 per carat guidance. Kimberley Underground's per carat prices at the tender were $236, lower than guidance yet Williamson prices achieved $243 per carat, which was above guidance.