ended Result
Nov 2015
  • Geneva (Switzerland)

  • address: 13, Quai du Mont Blanc - 1201

Auction summary

History was made at Sotheby’s auction in Geneva this week when the extraordinary Blue Moon diamond became the most expensive gemstone in the world.

The Blue Moon diamond - named after the expression “once in a blue moon” to emphasise its incredible rarity - caused a worldwide sensation when the original 29.62ct rough stone was found in South Africa in January last year. It hit the headlines again in September when the 12.03ct cut and polished diamond was unveiled at Sotheby’s London.

This week’s jewellery auction sealed the Blue Moon’s place in the history books when it sold for $48.5m, setting a new world auction record for any diamond, regardless of colour or type of gemstone. Now set into a ring, it also became the most expensive jewel to ever go under the hammer. Both previous records were held by the 24.78ct Graff pink diamond, which fetched $46.2m at Sotheby’s Geneva in 2010.

Read more about record-breaking diamonds at auction

At a breathtaking $4.02m per carat, the Blue Moon diamond also set a new auction record for the price-per-carat for any diamond or gemstone, beating the $3.34m per carat achieved by the Zoe Diamond sold at Sotheby’s auction in New York just last year. As expected, the magnificent stone aroused an intense nail-biting bidding frenzy in Geneva on Wednesday night. The final record-breaking bid was made by a private collector based in Hong Kong, who has renamed the diamond “The Blue Moon of Josephine”.

David Bennett, Sotheby’s Worldwide Chairman of Jewellery, said: “I am absolutely delighted with this evening’s record result - this show-stopping blue diamond is surely a once-in-a-lifetime stone.”

The Gemological Institute of America declared the cushion-cut blue diamond internally flawless and has graded it Fancy Vivid blue, which is the highest possible colour grading. New York-based Cora International LLC, which purchased the original rough stone from Petra and spent six months cutting and polishing it to perfection, was also thrilled with this week’s Sotheby’s auction result. Ehud Laniado, Chairman of Cora International LLC, said: "This diamond is a true gift of nature. The GIA graded 400 blue diamonds and only four of them were graded Fancy Vivid blue. So even among this extremely rare class of blue diamonds, to get one vivid blue, 12 carats, internally flawless, is really as rare as a ‘blue moon’.”

Read more about the history of blue diamonds here

By Åse Anderson

With an estimate of $35-55 million, Sotheby’s unveiled a magnificent coloured gemstone today in London that looks set to become the most expensive blue diamond in the world.

Named the Blue Moon in reference to its “once in a blue moon” discovery, when it goes under the hammer at Sotheby’s Geneva on 11 November 2015, the 12.03ct diamond will be the largest cushion-shaped fancy vivid blue diamond ever to appear at auction. The current record holder of the most expensive blue diamond is the 9.75ct Zoe Diamond, which was sold for $32,645,000 at Sotheby’s New York in November last year.

Read more about record-breaking diamonds at auction

At the presentation of the Blue Moon diamond, David Bennett, worldwide chairman of Sotheby’s International Jewellery Division, described it as “an extraordinary and magical stone with an entrancing colour”. The diamond has not only achieved the highest possible colour grading for blue diamonds, it has also been declared internally flawless by the Gemological Institute of America (GIA), which said in its report: “While any diamond with natural blue colouration is a rare discovery, some are so exceptional that they emerge only once in a lifetime. The Blue Moon diamond is one of those remarkable occurrences.”

The Blue Moon diamond was cut from a 29.62ct rough blue diamond, which was found by Petra Diamonds in the South African Cullinan mine in January 2014. The rough stone was bought by New York-based Cora International, which has spent six months cutting and polishing it into the exquisite gem unveiled today.

David Bennett added: “The tremendous excitement last year over the discovery of a 29.62ct rough blue diamond at the Cullinan mine in South Africa has now been totally justified. Blue, for me, is the most mysterious and magical of all the diamond colours, and the Blue Moon will now take its place among the most famous gems in the world.”

Read more about the history of blue diamonds here

Highlights Highlights

The 12.03ct cushion-cut Blue Moon diamond sold for $48.5m, smashing three world auction records in one fell swoop to become the most expensive gemstone or jewel to ever be sold at auction, as well as achieving the highest price per carat for any gemstone - diamond or otherwise. 


  • Geneva: Switzerland
  • address: 13, Quai du Mont Blanc


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