Sotheby’s will be offering a 7.03-ct. fancy vivid blue diamond from the Cullinan diamond mine at its sale of Magnificent Jewels in Geneva, May 12 at the Beau-Rivage Hotel.

The internally flawless, cushion-shaped diamond, which was cut from a 26.58-ct. rough, was discovered in 2008 at Petra Diamonds’ historic diamond mine in South Africa. The pre-sale estimate is from $5.8 to $8.5 million and the buyer will have the honor of naming the diamond.

Sotheby’s said the diamond ranks among the most important blue diamonds ever to be offered for sale by venerable auction house. The Gemological Institute of America has graded the stone as fancy vivid blue in color and internally flawless in clarity, the highest possible grading for a blue diamond.

Blue diamonds, which are among the rarest of all gems, owe their color to the presence of the chemical element boron during the stone’s formation. The Cullinan mine is the world’s most consistently reliable source of blue diamonds, Sotheby’s said.

“This stone certainly ranks among the most important blue diamonds that I have had the privilege of offering for sale in my career at Sotheby’s and what makes it particularly special for us, is that we’ve been able to follow its production from the initial rough state through the various stages of its cutting and polishing,” said David Bennett, chairman of Europe & the Middle East, Sotheby’s International Jewellery department.

JCK