Prices for Argyle diamonds increased 10% during the period, with second quarter production of 7.53 million carats compared with 7.26 million carats in the previous corresponding period.

“Ashton expects the half year pre-abnormal profits to be 10-20% above last year’s full year pre-abnormal profit result,” chief executive officer, Doug Bailey, said in a statement.

Ashton has a 40.1% stake in the Argyle mine, with Rio Tinto holding 59.7% and public investors the remaining 0.2%.

The company’s wholly-owned Merlin Mine produced 44,755 carats in the second quarter, with first half sales totalling US$7.1 million, an average of US$113 per carat. It also recovered the largest gemstone so far at Merlin, 26.92 carats.

The diamond miner said it has sold an additional 16% interest in its Mt Weld Rare Earths and Tantalum Projects to Lynas Corporation, and completed its stock buy-back. Ashton purchased 5% of its issued capital, equivalent to 16.6 million shares.

Ashton is 47% owned by Malaysia Mining Corp.