Sycamore and three other mining companies had made takeover bids for the mine, which has been out of production since Canada’s Semafo placed it under care and maintenance in 2014 and sold it to New Dawn Mining.
"Sycamore's was the winning bid, and we signed an outline agreement today," Abdoulaye Magassouba, Guinea's minister of mines and geology, said late on Tuesday.
The deal requires Sycamore to set up a Guinea entity to deliver a feasibility study within 180 days, after which the government will grant a mining licence.
It also requires Sycamore to immediately inject $5 million into the Guinea entity, and eventually invest $35 million more towards exploitation and potential extension of the mine.
"We aim to redevelop this plant as fast as possible, by restarting the mine with the strongest possible production," Sycamore Mining Chief Executive Matthieu Sharples said as he signed the agreement in the capital, Conakry.
Sycamore Mining did not immediately respond to requests for comment on Wednesday.
Kiniero lies 591 km (367 miles) east of Conakry.
By Saliou Samb
