Firestone Diamonds said it reached earthmoving and production plant capacity targets ahead of schedule and recovered a high quality diamond at its BK11 mine in Botswana, raising its expectations for the average value of output at the mine.
It said early diamond recoveries included 13.74 carat stone, with value estimated at $5,000 per carat.
"This recovery is very significant and confirms our expectation that larger diamonds will be recovered at BK11," Chief Executive Philip Kenny said in a statement.
Firestone said it would "comfortably exceed" the target production of 1.5 million tonnes per annum at it BK11 production plant once the phase 2 commissioning was completed in the fourth quarter of 2010.
Firestone, which had agreed to buy rival Kopane Diamond Developments for $71 million to get its hands on Kopane's Liqhobong kimberlite project in July, said plans developed in relation to the mine were in advanced stage.
However, the company said a plant it was building for Debswana Diamond Co at a Botswana mine would be delayed to allow Debswana to focus on certain higher priority projects.
The construction of the modular tailings treatment plant at the Jwaneng mine had been expected to start in the first half of 2011 and reach full production in late 2012, said the diamond miner and explorer with operations in Botswana and South Africa.
Shares of Firestone were up 5.4 percent at 24.75 at 0748 GMT on the London Stock Exchange. They touched a high of 11.8 percent earlier in the session.