A flawless blue 7.03 carat diamond was sold at Sotheby’s this week for £6.2 million.

We reported on this diamond a few weeks ago, and it was sold at auction in Switzerland on Tuesday for US$9.5 million (about £6.2 million) or US$1.35 million per carat, establishing a new record price per carat for any gemstone sold at auction and the highest price for a fancy vivid blue diamond sold at auction.

Blue diamond weighing 7.03 ct. Photo: Petra Diamonds

The important fancy vivid blue, internally flawless, cushion-shaped diamond weighing 7.03 carats sold on Tuesday evening — following a frantic 15 minute telephone bidding war — as the centrepiece of Sotheby’s Magnificent Jewels auction in Geneva.

This sale price surpassed the world record price per carat achieved for any gemstone at auction, which was formerly held by a 3.73 carat, fancy vivid blue pear-shaped diamond which sold for US$1.33 million per carat at a Sotheby’s auction in May 2008. It also surpasses the world record for a fancy vivid blue diamond sold at auction, which was formerly held by a 6.04 carat, fancy vivid blue diamond ring which sold for US$7.98 million at a Sotheby’s auction in October 2007.

The blue diamond ranks among the most important diamonds ever to be offered for sale by Sotheby’s.  It was cut from a 26.58 carat rough discovered in 2008 at Petra Diamonds’ historic Cullinan diamond mine in South Africa, the world’s most consistently reliable source of blue diamonds.

The Cullinan mine was previously owned by De Beers and it famously produced the Cullinan Diamond, the world’s biggest ever uncut gem diamond, which weighed in at 3,106 carats when it was discovered back in 1905.  The main diamonds that were cut from the Cullinan ended up in the Crown Jewels.

The Gemological Institute of America (GIA) has graded this blue diamond as fancy vivid blue in colour and internally flawless in clarity, the highest possible grading for a blue diamond.

The price of $9.5m exceeded the pre-sale estimate which was in the range of $5.8m to $8.5m, and it shows that there is still some money out there for exceptional diamonds; indeed the diamond wider diamond industry will take some encouragement from the price achieved for this diamond, although it is reported that some of the other pieces in the sale sold at disappointing prices.

The identity of the buyer of the diamond is revealed to be Joseph Lau Luen-Hung, a Hong Kong real estate developer who is reported to be Hong Kong’s fifth wealthiest person.  Sotheby’s claim that the diamond has been named “Star of Josephine” by its new owner.

There’s a video of the bidding process and the diamond at Sotheby’s on the BBC website here.