Rio opens underground diamond mine April 30, 2013 - 2:48PM The move from open pit mining to an underground operation will extend the life of Argyle until at least 2020. The average annual production over the life of the underground mine is likely to be 20 million carats per year. Rio Tinto diamonds and minerals chief executive Alan Davies on Tuesday said the Argyle mine had produced some of the world's most spectacular diamonds. "The new Argyle underground mine has allowed us to extend the life of this iconic asset for Rio Tinto and Western Australia," he said. The Argyle mine has produced some 800 million carats of rough diamonds over the past 25 years, including a small but consistent supply of the world's rarest pink diamonds. Argyle Diamond Mine managing director Kim Truter said the Argyle Diamond Mine is a world-class resource, which has been strongly supported by Rio Tinto since exploration began in the 1970s. "A new chapter begins at Argyle and I am proud to acknowledge the many men and women who have contributed to the discovery and development of the mine and the production of some of the best diamonds the world has ever seen," he said. Rio Tinto is one of the world's major diamond producers through its 100 per cent control of the Argyle mine in Australia, 60 per cent of the Diavik mine in Canada, a 78 per cent interest in the Murowa mine in Africa and 100 per cent interest in an advanced diamond project in India.