Synthetic-diamond makers received a boost in January when the Gemological Institute of America--the organization that invented the color, cut, clarity and carat diamond standards 50 years ago ...

Graff chairman Laurence Graff with the 102.79-carat Constellation, the world's largest D-colour, internally flawless round diamond, which was cut from Graff's Light of Letšeng 478-carat rough.

By comparison, the second-largest gem-quality rough diamond, the famous Lesedi La Rona which was discovered in 2015, weighs just over a third of the Cullinan, at 1,109 carats.

rated as a Type IIa, which means the rough-cut diamond contains very little or no nitrogen atoms and is virtually flawless. The 404ct diamond is less than half the size of the masterpiece ...

At the same time, diamond-producing nations are no longer content with just mining the rough diamonds. They want to cut and polish them, too. African cutters may now cut into India’s profits.

Mr. Graff initially had 66 stones, ranging in size from less than a carat to around 26 carats, cut from the rough diamond. They were presented in groups, beginning last November.

When the hammer fell at Sotheby's London on June 29, 2016, after bidding for the show-stopping 1,109-carat rough cut diamond known as the Lesedi la Rona reached $61 million but failed to surpass ...

Graff chairman Laurence Graff with the 102.79-carat Constellation, the world's largest D-colour, internally flawless round diamond, which was cut from Graff's Light of Letšeng 478-carat rough.