The London listed diamond miner pointed out, however, that $16 million have reversed since the period end due to the strengthening of the rand. Production was up 64% to 953,553 carats.
The diamond miner reported a loss per share of 5.23 cents for the first half from earnings per share of 6.79 cents a year ago. Adjusted EPS before unrealised foreign exchange movements and non-recurring transaction costs rose to 2.46 cents from 0.86 cents previously.
Revenue was up 13% to $101.4 million due to increased production, offset by the weakening in rough diamond prices experienced since July 2011 following on from the prevailing climate of global economic uncertainty led by the Eurozone sovereign debt crisis.
Profit from mining activity grew 25% to $30.7 million reflecting the introduction of Finsch into the group from 14 September and the continuing improvement of the mines' performance under Petra management - all in turn significantly mitigated by the weaker diamond prices.
Adjusted EBITDA was 24% higher at $25.0 million.
The weakening in rough diamond prices from July to December 2011 resulted in Petra's gross revenues being approximately $23 million lower than management's expectations for H1 FY 2012.
"It is important to note that both production and sales are expected to be substantially higher in H2, due to a full six months' contribution from Finsch and the release of unusually high Group closing H1 inventory into H2 sales," the company said.
The company's first tender for H2 FY 2012 was concluded in early February and revenues of $44.4 million were achieved on the sale of 306,149 carats. In H1 Petra held three sales tenders, while in H2 five tenders are scheduled, again supporting management's confidence in substantially higher H2 revenues.
Gross mining and processing costs for the SA operations increased in Rand terms by approximately 19% due to the contribution of Finsch towards these costs, partially offset by a weakening Rand to effect an 8% increase in US Dollar terms.