The De Beers Centenary Diamond is, at 273.85 carat, the third-largest diamond to have been produced in the Premier Mine. Among top-color diamonds, only the Cullinan I and II are larger than the Centenary diamond.[1] The Centenary Diamond is rated in color as grade D color by the Gemological Institute of America, which is the highest grade of colourless diamond and is internally and externally flawless. It was named the Centenary Diamond as it was presented in the rough for the Centennial Celebration of De Beers Consolidated Mines on 11 May 1988. The Centenary Diamond was unveiled in final form in May 1991.
Discovery
The Centenary Diamond was discovered in the Premier Mine on 17 July 1986 using their X-ray imaging system. The original rough was 599 carat and it was presented on 11 May 1988 in the Centennial Celebration of the De Beers Consolidated Mines. As then-chairman Julian Ogilvie Thompson said, "We have recovered at the Premier Mine a diamond of 599 carat which is perfect in colour – indeed it is one of the largest top-colour diamonds ever found. Naturally it will be called the Centenary Diamond."
Cutting the Centenary
Cutting such an immense and valuable diamond required expertise and a considerable investment. Gabi Tolkowsky was chosen to head the team responsible for cutting the Centenary Diamond, along with Geoff Woolett, Jim Nash and Dawie du Plessis, assisted by a specially-picked group of engineers, electricians and security guards to facilitate in the work on Centenary Diamond.