By Cecilia Jamasmie World’s No.2 miner Rio Tinto (ASX, LON, NYSE: RIO) said Thursday it had sold its 40% stake in the world’s second-biggest copper mine, Grasberg, for $3.5 billion to Indonesia’s state mining company PT Inalum. Rio had a joint venture with Freeport-McMoRan (NYSE:FCX), operator of Grasberg, for a 40% share of Grasberg’s production above specific levels until 2021 and 40% of all production after 2021. Freeport separately said it will receive $350 million from PT Inalum after the stake sale.