Net income from diamonds almost doubled to $104 million during 2014.
Global miner Rio Tinto posted a 6-percent rise in diamond revenue on the year before in 2014 to $901 million.
Rio Tinto's diamond has a 100-percent stake in the Argyle mine in Australia, and owns 60 percent of the Diavik mine in Canada and 78 percent of the Murowa mine in Zimbabwe.
Rio said that diamond production dropped 13 percent on the year to 13.87 million carats, mainly due to lower recoveries at the Argyle mine as it moved from an open-pit to underground mining. However, the company said that revenue and profit at its diamond operations were strengthened by a 6 percent increase in average rough diamond prices last year.
The Argyle underground mine is on track to reach full capacity in 2015, the miner said, and projects group output rising to 21 million carats this year.
Looking ahead to the rest of this year, Rio Tinto said that global economic growth would probably stay modest and that current market volatility indicated that 2015 would be "challenging".
