(IDEX Online) - An exceptional 39.34-carat blue rough diamond has been sold for over $40m.The Type IIb diamond (pictured), was recovered by Petra at its Cullinan mine, South Africa, in April, and was sold yesterday for an up-front cash payment to a partnership between De Beers and Diacore.The price paid was $1,021,357 per carat, slightly less than the $1,156,000 per rough carat paid for another diamond from the same mine, The Blue Moon of Josephine.The Blue Moon was bought by New York-based Cora International for $25.6m, transformed into a 12.03-carat fancy vivid internally flawless cushion-cut stone, and sold at Sotheby's to Hong Kong billionaire Joseph Lau for $48.5m at the highest ever price per polished carat, of $4m.Richard Duffy, Petra's CEO, commenting on the sale of the 39.34-carat stone, said: "This sets a new milestone for Petra in achieving its highest price for a single stone and follows the sale of the 299 carat Type IIa white diamond in March this year and the five blue diamonds comprising the Letlapa Tala Collection in November 2020, purchased by the same De Beers Diacore partnership."