Diamond production from three mines of Rio Tinto, amounted to 3.497 million carats, in the first quarter of 2010, indicating a drop of 36 percent, reports say. The decreased output from individual mines during the said quarter, was attributed by the company as; a lower feed grade at its fully-owned Argyle mine and frequent stoppages of the process plant due wet weather causing production at Argyle to drop by 43 percent to 2.531 million carats, output at the Diavik mine (Rio Tinto holds 60 percent stake) decreased 12 percent to 938,000 carats, with 6 percent of those sourced from underground operation which was launched in March. The lower volumes processed, ‘as planned’ were the cause of decreased production at Diavik, as reported. Also production dropped 6 percent to 29,000 carats at Murowa mine ( the company owns 78 percent share).