Rio Tinto has signed a letter of intent with diamond explorer BRC DiamondCore, in which Rio will invest $13 million in five diamond exploration projects of BRC in the Democratic Republic of Congo (DRC), and earn a 60 percent interest on the same. %% The five projects are a cumulation of 106 exploration permits for exploration over 27,000 sq km in the Equateur and Oriental Provinces in northern DRC. These projects are believed to be prospective for hosting diamondiferous kimberlites. %% The exploration will be two-phased. Rio Tinto can invest $3 million in each project and n earn a 35 percent interest, although it has to make its investment by December 31, 2012. In phase two, Rio Tinto can invest an additional $10 million by end-2014, which will give it a further 25 percent interest earning. Once the projects stand complete, Rio and BRC would form a 60:40 joint venture.