The auction house said it expected the 15.10-carat De Beers Cullinan Blue diamond to sell for more than US$48 million.

The diamond is the “largest internally flawless step cut vivid blue diamond” ever graded by the Gemological Institute of America (GIA), Sotheby’s said in a statement.

The sale will mark the first time a blue diamond of more than 15 carats has ever gone under the hammer, the press release added.

Sotheby’s said the diamond, which previewed in New York this week, would be offered on a yet-to-be determined date during its Hong Kong Luxury Week in April.

It was cut from a rough stone discovered at the Cullinan mine in South Africa in April 2021.

The diamond is bigger than the Oppenheimer Blue, a 14.62 carat stone that set the world record price for a blue diamond at auction in May 2016 when it sold for US$57.5 million.

Earlier this month, Sotheby’s in London sold the Enigma – the largest cut diamond ever to come to auction at 555.55 carats – for £3.16 million.