A 1,098 carat diamond believed to be the third largest gem-quality stone ever to be mined, has been discovered in Botswana. The stone was presented to President Mokgweetsi Masisi on Wednesday by the Debswana Diamond Company. The world's largest diamond is the 3,106 carat Cullinan stone found in 1905, while the second largest was found in Botswana in 2015.