Botswanas Jwaneng diamond mine had record production last year. This is not likely to be repeated for many years as the operation moves to lower grade areas according to reports by Reuters. Botswana is the worlds leading diamond producer by value and accounts for nearly two thirds of output from De Beers, of which mining group Anglo American plc owns 45%. The open pit mine, jointly owned by diamond giant De Beers and the Botswana government, produced 15.6 million carats last year, a life high and up 15% from 2004. But output is expected to fall by up to 10% this year, the mines General Manager Dale Ekmark told Reuters during a visit to the mine on Wednesday. The mine is expected to match record ore production of 10 million tonnes, but the ore will have fewer diamonds.

"The grades will be lower so the carat production will be down. Our budget is 14.1 (million carats) and our stretch target this year is 14.4 and as of today, we are 8,000 carats ahead of that stretch target," he said. Mining managers last year at Debswana - a 50-50 joint venture of De Beers and the government - scrambled to adjust plans when two accidents at the firms other huge mine, Orapa, meant production would fall there. To help maintain overall production from Debswana, Jwaneng exploited higher grade areas and cut down on stripping -- where waste rock is dug out to expose the rich volcanic "pipes" of kimberlite that contain gems. As a result, Jwaneng has a backlog of waste-rock stripping and must tackle lower-grade areas delayed from last year.%%The mine must cart off four tonnes of waste rock for every tonne of ore in massive trucks that carry 240 tonnes each. "It is highly unlikely that we will achieve 15.6 again," Ekmark said. "The long-term outlook is 12-14 million carats per year." A programme to cut costs and improve revenues recently launched throughout Debswana, however, might help boost those production targets, he added. For instance, the main treatment plant at Jwaneng has been operating at 82% capacity but the target was to move this into the 90s. A new treatment plant will have to be built in coming years because more ore has been found in the ground underneath the current plant and the pit will be expanded to exploit that. The mine, where production was launched in 1982, is preparing to shift over the next decade from open pit operations to underground mining, Mining Manager James Kirby said.%%An exploration shaft is due to be dug next year with construction being launched the following year for a main shaft. Underground production is due to start in 2016, and ramp up until full output is achieved in 2020. Based on current resources of the mine, the underground operation is expected to run for 15 years, but exploration activity is continuing to find new deposits, he said. Jwanengs production made up nearly half of Debswanas total output of 31.9 million carats last year.