LONDON-listed diamond miner Petra Diamonds returned to profit in the 2013 financial year, as production and revenue growth offset above-inflation cost increases.

Petra posted basic earnings per share (EPS) of 6.3c for the year ended June 2013, from a loss of 0.48c a year ago, and adjusted EPS of 10.31c from 7.82c a year ago as production rose 21% for the year to 2.668-million carats.

Revenue was 27% higher at $402.7m and profit from mining activity grew 34% to $138.6m. The group reported net profit after tax of $27.9m after a $2.1m loss the previous year.

CEO Johan Dippenaar said the 2013 financial year "marked a further year of solid growth" in production, revenue and underlying profitability, while expansion programmes at Finsch and Cullinan gathered momentum.

"We have kept our costs and capital expenditure well controlled, maintaining our robust financial position," he said. Petra was on track to reach its production target of 3-million carats in financial 2014, and 5-million carats by financial 2019, Mr Dippenaar said.

While some of its South African mines were affected by industrial action that began on August 29 2013, Petra said normal operations were expected to resume at those mines from Monday. Strong production at the start of the 2014 financial year, and partial production during the industrial action, meant the full-year production target was still in sight.

Petra said it expected the rough diamond market to remain steady in 2014 due to constrained supply and a firmer US market, the world’s major market for polished diamonds, as well as continued growth in China, albeit at a lower rate than over recent years.