Rio Tinto (NYSE, ASX: RIO) officially opened Tuesday the underground operations at the Argyle diamond mine in northeastern Australia, reports the Australian Broadcasting Corporation.
The company said the open pit mine is almost exhausted, following about 25 years of production, and it will finish up this year.
By expanding under ground, the mine life will be extended until 2020 at minimum.
Rio Tinto forecasts the mine will produce 20 million carats a year and it will hit peak production in 2015.
The Argyle mine is still up for sale, the company said.
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