(IDEX Online) - Debswana's rough diamond sales rose by 37.5 per cent in the first nine months of this year, according to the Bank of Botswana. The 50-50 partnership between De Beers and the Botswana government sold $3.578 billion, an increase from $2.602 billion, as demand remained steady.Diamond revenue accounts for a fifth of Botswana's GDP and 70 per cent of its foreign revenue.The government has reportedly been lobbying for a larger share of the diamonds in its deal with De Beers, which has been extended but not re-negotiated as planned. It is reported to receive 25 per cent at present, up from 15 per cent agreed in 2011.The Debswana Diamond Company controls all the country's diamond mining, at the Damtshaa, Jwaneng, Letlhakane and Orapa mines.Pic shows Jwaneng mine