Canadian miner Lucara Diamond has sold its 813-carat diamond, called The Constellation, for a record-breaking $63.1 million.
But the record may not hold for long; Lucara is due to sell an even larger diamond - the 1,109-carat Lesedi La Rona - at Sotheby's London on June 29.
Both diamonds are Type IIa, one of the rarest types of diamond, with little or no impurities and no color.
Lucara's chief executive William Lamb said price paid by Dubai-based Nemesis International for The Constellation - equivalent to $77,647 per carat - was the highest ever achieved for a rough diamond.
He said Lucara had retained a 10 percent interest in the net profit from the sale of polished diamonds made from the stone.
In an interview with Gulf News on Monday, Nemesis International director Nickolas Polak said that his firm would now search for the "magic of the stone" in order to cut the most spectacular diamonds from it.
He admitted to feeling a little awed by the rarity of The Constellation.
"We feel like amateur artists who have found a Mona Lisa in the attic," Polak told Gulf News.
The Constellation was unearthed at Lucara's Karowe mine in Botswana in November.
The tennis ball-sized Lesedi La Rona was also found at the Karowe mine in November. According to Sotheby's, it is the largest rough diamond discovered since the 3,106-carat Cullinan Diamond was unearthed in Pretoria, South Africa, in 1905.
Sotheby's has put an estimate of $70 million-plus on the Lesedi La Rona, whose name the auction house said meant "our light" in Botswana's Tswana language.