The rough diamond, which was mined in Botswana, was sold by Lucara Diamond Corp for $17.5m (£13.5m) last week to an undisclosed buyer. Graff Diamonds subsequently revealed that it had made the purchase.
It said in a statement: “This impressive rough diamond of exceptional transparency and quality is said to be over three billion years old and was probably formed when the earth was still being created.
“It will now follow its destiny under the careful watch of Mr. Laurence Graff and his team of gemologists and master cutters.”
The stone was once the second largest diamond in history, originally weighing 1,500 carats but it broke when it was being recovered in November 2016. The larger piece of the diamond has failed to sell so far.