Friday, 22 April 2022

De Beers Cullinan Blue = $57.5m

Sotheby’s Hong Kong auctioned the largest and most valuable blue diamond ever - the 15.1 carat, internally flawless, fancy vivid step-cut De Beers Cullinan Blue. The 39.35 carat rough stone was discovered by Petra Diamonds in South Africa’s Cullinan mine in April 2021. The diamond has a value “in excess of $45 million.” There have been only five blue diamonds over 10 carats ever to appear at auction, and, until now, none of them has topped 15 carats.
The most expensive blue diamond sold at auction previously was the 14.63 carat Oppenheimer Blue, sold at Christie’s Geneva in 2016 for £44 million.
Petra Diamonds (LON:PDL) 39.34 carat Type IIb gem recovered at its Cullinan mine in April was sold to De Beers and manufacturer Diacore for $40.2 million. Petra’s Blue Moon of Josephine diamond, cut from a 29.6-carat rough blue diamond, sold for $48.5 million in 2015. The price of $4 million per carat remains the world record. The Blue Moon of Josephine lost about 59% of its mass during cutting. If the same holds for the 39.34-carat blue diamond, the result would be a 16-plus-carat gem. At $4m per carat, the polished stone would be worth $64m.

Diamonds get their natural blue color from small amounts of boron trapped in the crystal carbon structure during its formation.