It was a much talked about diamond which went to auction at Sotheby’s Geneva on 11 November and the result was just as exciting as the pre-sale tension. The 12.03 carat ‘Blue Moon’ diamond was bought by a Japanese billionaire for an incredible $48.4 million; a new world record for the price paid for a gemstone.

What is the story behind the Blue Moon Diamond?

The diamond which set hearts racing at the auction house was mined in January 2015 at the Cullinan diamond mine in South Africa. The industry was set alight by the size, color and purity of the stone and when in its rough state weighed 29.6 carats it was quoted as being ‘one of the most important blue mines ever recovered’. Purchased as a rough diamond in February for $25.6 million, the stone was then cut, shaped and polished before the resulting beauty was put into auction.

What is a blue diamond?

Blue diamonds are so called because of the amount of boron present in the gemstone. White diamonds have no trace elements in their make-up and blue ones are very rare. The Monograph GIA hue rating described the Blue Moon diamond as ‘likely to have never before been seen within such a large diamond, or any gemstone’ which meant it would have all gemology eyes firmly on it when  the day came for it to go up for sale.

What happened on the day of the auction?

Sotheby’s had given a pre-sale estimate price of $35-$55 million so the outcome was towards the upper end of the guide price. Whilst initially the name of the buyer was anonymous, it was quickly established that it had been sold to Japanese billionaire, Joseph Lau. The reason the buyer became apparent was because as soon as the diamond was sold, it was announced it had been renamed ‘The Blue Moon of Josephine’. At the auction the previous day, a pink diamond sold for an equally impressive price of $28.5 million with a similar message being broadcast that the gemstone was to be known as ‘Sweet Josephine’. Lau has a young daughter named Josephine and it was just a few hours later that it was confirmed he had bought them both as a gift for her.

What makes the diamond such a record breaking gem?

The name of the diamond ‘Blue Moon’ was originally given due to the industry opinion that a gemstone so large and perfect only comes around ‘once in a blue moon’. This was seen to be the case when the hammer went down and the previous record price for a gemstone was smashed. The title had been held since 2010 by the Graff Pink which had sold for $46.15 million, but even at 24.68 carats it was no match for the Blue Moon.

Not only the most expensive price paid for any gemstone, the Blue Moon also broke the record for the most expensive piece per carat.  The crown had been held by the 9.75 carat blue Zoe diamond when it sold for $3.3 million per carat in December 2014. The Blue Moon blew this away though at a hefty price tag of $4.02 million per carat.

With even the chairman of Sotheby’s David Bennett describing the Blue Moon diamond as ‘the blue diamond of my career’, the auction of 11 November was truly a once in a lifetime experience.