The diamond conglomerate De Beers, along with its affiliated companies like Anglo American, control ~80 percent of the world's diamond supply. With this. How the World's Oldest Diamond Monopoly is Trying to Become an IT dropped “tens of millions” of dollars on a portfolio of seven companies. It had the ability of one of the first companies to open mines, to start creating a monopoly power over the diamond harvesting throughout Africa. Gemological Institute of America. The Rio Tinto Group is a British-Australian multi-national company involved with mining minerals. Retrieved 27 November Mr Cleaver, an Anglo American veteran, became the boss of De Beers in July. Natural diamonds—as opposed to the synthetic ones mostly used in industry—were formed more than 1bn years ago deep below cratons, the oldest part of continents. Ina campaign by Global Witness to highlight the role of diamonds in international conflicts led to a review by the United Nations.