LONDON (Reuters) - Miner Rio Tinto has approved spending an additional $170 million to develop its Simandou iron ore mine project in Guinea on top of the $650 million it has already invested, the Anglo-Australian group said on Monday. ""Simandou will be the largest integrated iron ore mine and infrastructure project ever developed in Africa,"" said Sam Walsh, chief executive of the group's iron ore division. Mining is expected to be launched within five years at the mine, which is due to produce at least 95 million tons of iron ore a year, a statement said. The total cost of developing Simandou has been estimated at around $6 billion. The infrastructure will include a 650-kilometre railway to the coast and port facilities, Rio said. Last week, Rio signed a $1.35 billion deal with Aluminum Corp. of China (Chalco) for a joint venture on Simandou, billed as the world's largest undeveloped iron ore deposit. Guinea's Mine Minister told Reuters on Monday that he hoped the Rio-Chinese partnership would speed up development of the project, but said the government had not yet approved the deal.