(IDEX Online) - Tanzania's diamond revenue slumped by 55 per cent in the second quarter of this year, down from $38.4m to $17.4m.Production was also significantly reduced, from 108,165 carats to 63,973 carats, said the Bank of Tanzania. That's a drop of 41 per cent.Williamson (pictured), the country's only large-scale mine, was put on care and maintenance last year by UK-owners Petra.The mine was last year classified as an "asset held for sale" prompting speculation that it could be sold.Tanzania is reportedly looking to sell its rough through the Dubai Diamond Exchange as it seeks more lucrative markets for the estimated 500,000 carats it produces annually.