ANOTHER massive earthmoving operation to extend the life of the world’s richest diamond mine, Jwaneng in Botswana, will be taken to the board of Debswana for approval in the middle of next year, Albert Milton, GM of the mine, said on Tuesday.

The Jwaneng mine, which was officially opened in 1982, is an open-cast mine and is one of the world’s five super pits. It is owned by Debswana, which is jointly owned by De Beers and the Botswana government.

Anglo American owns 85% of De Beers and the Botswana government a 15% stake.

Debswana is busy with an enormous $3bn earthmoving operation called Cut 8 that pushes one edge of the pit back, allowing mining to continue safely to deeper levels to extract diamonds from the three kimberlite pipes, ancient volcanic flows, that make up the mine. By end-October, Jwaneng had exceeded its target of 7.76-million carats by 14%, producing 8.8-million carats.

Jwaneng produces on average about 10-million carats a year and the intention is to build output to 12-million carats in five years, not quite reaching the peak of 16-million carats in 2006.

The mine contributes two-thirds of Debswana’s annual earnings and is described by the firm as the world’s richest piece of real estate. Cut 8 will allow the mine to go to 650m below ground level from 350m.

It is a mind-bogglingly big project but the next cut, which goes before the board next year, will be bigger, Mr Milton said.

It takes up to six years to move the waste rock to open fresh mining areas. Cut 8 will move 680-million tonnes of earth while Cut 9, the project that will go before the board next year, will have to move 1-billion tonnes and take the mine to a depth of 850m.

The reason is that the push back on that side of the pit entails moving waste rock generated in Cut 5, and which is now near the pit as the mine has expanded over the years, he said.

To put the figures into context, during the development of Cut 8 about the same amount of rock will moved between 2010 and 2016 as the mine has extracted in the past 25 years, but Debswana reckons it will generate diamonds worth $15bn. It will probably be the last big expansion of the Jwaneng pit before mining moves underground, Mr Milton said.

Work has begun on a study on whether to put in a further push back, Cut 10, or go underground by sinking a shaft and tunnels to extract diamonds. If the latter option is chosen, it will be the second mine where De Beers has decided to go underground. Last month it launched the start of a R20bn project to build an underground mine at its Venetia opencast mine in northern Limpopo.

The economic feasibility of Cut 10 is undermined by the need to further move the Jwaneng processing plant, parts of which had to be moved to accommodate Cut 8, Mr Milton said. The mine is 2.7km long and 1.8km wide.

"My feeling is that we’ll go for the underground option but we’ve not finished the trade-off study yet, between Cut 10 and underground," he said.

Jwaneng will start mining from Cut 7 in the middle of next year and from Cut 8 in 2017, adding 11 more years of mining to the project, the mine’s senior finance manager, Victoria Lekoma, said. A further complication comes with the limited space left for Jwaneng to store waste.

Management wants to appropriate land from the nature reserve it has set up alongside and ask the government to give it more land in the sparsely inhabited area to maintain the reserve at 6,500ha, Mr Milton said.