PETRA Diamonds said full-year production nearly doubled, mainly due to the contribution from its Finsch mine, and that it would sell its fissure mine operations in South Africa to focus on its core assets.

Petra, which has interests in seven producing mines in South Africa and one in Tanzania, said it would sell its fissure mine operations, comprising the Helam, Sedibeng and Star mines in South Africa. "The fissure mines are no longer core to the group," CE Johan Dippenaar said.

"Petra's management teams are focusing their attention on the group's major assets, as it is from these that production growth to over 5-million carats per annum by full-year 2019 will be delivered."

The FTSE 250 company said it produced about 2,2-million carats during the year. The Finsch mine - South Africa's second-largest diamond operation by production, which Petra bought from De Beers in September last year - contributed about half of the overall output in the year.

Revenue for the year ended June 30 rose 44% to $316,9m. Analysts were expecting the company to report revenue of $324,26m, according to Thomson Reuters.

Revenue growth was affected by the volatility of the diamond market and overall weaker prices, Petra said.

Diamond prices have fallen since the beginning of this year, on weaker demand amid the eurozone crisis and a slowdown in growth in key diamond markets China and India.