(IDEX Online) - Debswana has approved a $1bn investment to enable underground mining at Jwaneng, its biggest deposit.Work will start in May on a drilling platform for the comprehensive sampling of kimberlite pipes, it said today (10 January).Jwaneng opened in 1982 as an open pit operation run by Debswana, a 50:50 joint venture between De Beers and the Botswana government. Open pit operations are expected to end in 2032 but underground mining could extend Jwaneng's life to 2050 or beyond.It currently represents about 40 per cent of De Beers total production (10.3m carats in 2022)."Jwaneng stands proudly as the world's greatest diamond mine," said Al Cook, De Beers Group CEO and Debswana deputy board chairman."It is a central pillar of both the Botswana economy and the De Beers Group business."The global supply of natural diamonds is falling, so moving forward with the Jwaneng Underground Project creates new value for investors, brings new technology to the country, creates new skills for our workforce and provides new gems for customers around the world."Three quarters of Debswana's production is currently sold by De Beers. But under a new deal agreed last June, the state-owned Okavango Diamond Company (ODC) will see its share increase over the next decade from 25 per cent to 50 per cent.Pic shows Jwaneng mine.