Rio Tinto, Chinalco and the International Finance Corporation have signed a $US20 billion deal to develop iron ore deposits in the Republic of Guinea.
The trio said the Simandou project, which has been delayed for years, would be the biggest iron ore and infrastructure project developed in Africa.
The BBC reports the deal will now go the Guinean National Assembly for ratification.
If ratified, the three parties said they would complete a feasibility study, including timeline and costs, within about a year.
"This project is of critical importance for the people of Guinea,'' said Republic of Guinea president Alpha Conde.
"It's a nationwide priority that goes beyond the mines and far beyond our generations. With transparent and fair deals, our mining sector has the potential to be a game changer for Guinea."
As well as mining the iron ore, the three partners said they were working together to raise the funds to build a 650km railway and a deep-water port to transport the rocks and minerals.
They said the project had the potential to double Guinea's GDP and create 45,000 jobs.
Rio Tinto will take a 46.6% stake in the project, Chinalco 41.3%, Guinea 7.5% and IFC 4.6%.