query: What is the biggest diamond?
passage: Cullinan Diamond
The Cullinan Diamond is the largest gem-quality rough diamond ever found,[2] weighing 3,106.75 carats (621.35g), discovered at the Premier No. 2 mine in Cullinan, South Africa, on 26 January 1905. It was named after Thomas Cullinan, the mine's chairman.
passage: Centenary Diamond
The Centenary Diamond was discovered in the Premier Mine on 17 July 1986 using their X-ray imaging system. The original rough was and it was presented on 11 May 1988 in the Centennial Celebration of the De Beers Consolidated Mines. As then-chairman Julian Oglivie Thompson said, "We have recovered at the Premier Mine a diamond of which is perfect in color – indeed it is one of the largest top-color diamonds ever found. Naturally it will be called the Centenary Diamond."