Ivanhoe Mines and Zijin each hold now an indirect 39.6% interest in the Kamoa-Kakula project, thought to be Africa's most significant deposit of the red metal ever found.
Companies are pressing the government to better regulate public consultations and votes on mining projects, as they see legal uncertainty as the industry's main current challenge.
Only last year CAR was allowed to resume diamond exports after a three-year ban that tried preventing armed groups from financing a bloody inter-religious conflict.