Largest Flawless Diamond Centenary Diamond

273.85 carats, D-color, Flawless, modified heart-shaped Centenary Diamond.  Photo courtesy: De Beers

The Centenary diamond is said to be the largest, faceted, D-color, flawless diamond in the world

• 273.85-carat 
  
• Type IIa  
• D-color diamond 
• Modified heart-shape
• Internally flawless IF
• 50.50 x 39.90 x 24.55 mm.
• 247 facets, 164 on the crown and the pavilion, and 83 around the girdle.

The Centenary diamond gets its name from the centenary of the De Beers Consolidated Mines Ltd. celebrated on March 11, 1988. The Centenary rough diamond was actually discovered on July 17, 1986, at the Premier diamond mines, but all those involved in the discovery were sworn to silence. The closely guarded secret of the De Beers Mining Company was unveiled to the world only on March 11, 1988, at a special banquet held to mark the centenary, by the Chairman Mr. Julian Oglivie Thompson, who christened the stone the "Centenary Diamond".

The diamond rough weighs an enormous 599-carat. In it's rough form the Centenary diamond resembled an irregular match box with angular planes, a prominent horn like structure jutting out at one corner and a deep concave on the largest flat surface. The team decided to eliminate the protruding horn, the large cracks at the edge of the stone, and other superficial flaws before it got down to actually shaping the diamond.

The team decided not to use laser or saw for the initial steps of the cutting, to remove cracked material and other superficial defects. This was done to prevent the heating and vibrating of the diamond. Instead they adopted the traditional method of kerfing by hand, a process that is slow and time consuming. It took the team 154 days, to cut and remove 50 carats of cracked material. After this was completed they were left with a roughly egg-shaped stone weighing about 520 carats.

After removing the surface irregularities, the team embarked on the difficult task of taking accurate measurements , and drawing appropriate designs, that may possibly suit the egg-shaped stone. The team finally presented 13 different designs to the De beers board, with a strong recommendation in respect of one design, viz. the modified heart-shape. The Board accepted the modified heart-shape as it's choice, and then the final process of faceting the Centenary began in March 1990. The faceting was finally completed after nearly 10 months of painstaking work in February 1991.

Gabi Tolkowsky examining the Centenary Diamond. Photo courtesy: De Beers

While the Centenary diamond has never been appraised for it's value, it is known to have been insured for around $100 million at the time of it's unveiling in May 1991.

Whether De Beers still owns the Centenary, or whether the stone has been sold is still a mystery. Gabi Tolkowsky has said that he believes that the gem has been sold, but De beers declines any comment.

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