NEW YORK (TheStreet) -- Rio Tinto (RIO) - Get Report, Chinalco Mining and the International Finance Corp. have agreed upon investment terms to develop an iron ore mining project in southeast Guinea, the companies announced Monday. The $20 billion deal, which provides a framework on legal and financial matters, will need to be ratified by the Guinean National Assembly. 

The project would see the Guinea government control a 7.5% stake, while Rio and Chinalco will hold a majority stake with a 46.57% and 41.4% interest, respectively. The project will be the largest combined iron ore mine and infrastructure venture developed in Africa. 

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"Today is an important milestone in the development of this world-class iron ore resource for the benefit of all shareholders and the people of Guinea," said Rio CEO Sam Walsh in a statement. 

By early afternoon Tuesday, Rio Tinto shares had slipped 0.59% to $54.30.

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