Rare 10-carat blue diamond could fetch $20M at auction

A rare 10-carat blue fancy diamond could fetch up to $20 million when it goes to auction in Geneva on May 13, auction house Sotheby’s said on Thursday.

The cushion-shaped piece, known as the “Mediterranean Blue Diamond,” was mined in South Africa and classified as a “fancy vivid blue,” the highest grade for coloured diamonds.

“The market for coloured diamonds continues to go from strength to strength,” Jessica Wyndham, Sotheby’s head of high jewellery sales in Geneva said in a statement.

The Mediterranean Blue was cut from a 31.94-carat rough diamond discovered in 2023 at the Cullinan mine in South Africa. Its transformation into a polished gem followed a year of study and six months of planning and cutting, Sotheby’s said.

Diamonds of this calibre are exceptionally rare. Fancy vivid blue diamonds over 10 carats have consistently commanded high prices at auction.

In 2016, a 14.62-carat gem known as the “Oppenheimer Blue” sold for 56.8 million Swiss francs ($68.7 million) at Christie’s in Geneva, setting a world record or a fancy vivid blue diamond sold at an auction.

That same year, a 24.18-carat intense blue diamond found at Petra Diamond’s (LON:PDL) Cullinan mine in South Africa in 2014, sold for $25 million at a Christie’s auction in Geneva.