The rarest blue-green diamond on Earth is heading to auction, with experts predicting it could fetch up to £9.4 million ($12.8 million). Known as the 'Ocean Dream', this extraordinary gem was discovered in its rough form in Central Africa in 2002.
Discovery and Transformation
The original crystal weighed 11.17 carats before being expertly cut to preserve and maximise its stunning colour. The final gem now weighs 5.50 carats, making it the largest diamond of this colour ever recorded. Tobias Kormind, Managing Director of 77 Diamonds, described it as 'quite simply, in a category of one'. He added: 'This is the largest fancy vivid blue-green diamond ever certified by the GIA in its entire history. There is no other diamond of comparable colour and size anywhere on record. It is a perfect blend of two of the rarest diamond colours to exist.'
Geological Rarity
While most diamonds are colourless, they can occur in a range of colours due to trace elements or radiation during formation. The Ocean Dream is categorised as a 'fancy vivid blue-green diamond' by the Gemological Institute of America (GIA). This colour results from prolonged exposure to natural radiation deep within the Earth over millions of years, making it so uncommon that it borders on geological singularity.
Tom Moses, Executive Vice President and Chief Research and Laboratory Officer of the GIA, remarked: 'I could spot it from across the room! I have never seen a natural blue-green diamond of this intensity of colour, size, and it is a Type Ia, which certainly makes it a unicorn.'
Exhibition and Auction History
In 2003, one year after its discovery, the diamond was one of seven exhibited at the Smithsonian Museum in Washington DC. D. Jeffrey Post, curator of the National Gem Collection at the Smithsonian Natural History Museum, recalled: 'The Ocean Dream was one of seven rare and spectacular diamonds in our internationally acclaimed "Splendor of Diamonds" exhibition; it was one of the most popular special exhibits ever hosted at our museum.'
Eleven years later, the diamond sold at auction in Geneva for £6.6 million ($9 million). Now, it returns to the auction block at Christie's Geneva, where experts predict it could sell for even more. Kormind noted: 'When legendary fancy coloured diamonds come to auction, the market responds. The 14.62 carat Oppenheimer Blue sold for $57.5 million in 2016 and the 12.03 carat Blue Moon of Josephine for $48.4 million in 2015. The Ocean Dream is a different proposition entirely – rarer in colour than either, and seen at auction only once before. For the right collector, this is a once-in-a-lifetime acquisition, and I believe its high estimate of CHF 10m (approx $12.8m) could prove conservative indeed.'
Key Specifications
- Discovered: Central Africa, 2002
- Weight: 5.50 carats
- Colour: Fancy vivid blue-green
- Estimated value: £9.4 million ($12.8 million)
- Auction date: 13 May 2026
The diamond is currently set in a ring mount with sculpted rock crystal, round diamonds, and pink diamonds. Its triangular brilliant-cut shifts between oceanic blue and vivid green depending on the light.
Recent Discoveries
This news follows the recent unearthing of an 'astounding' half-pink diamond weighing 37.41 carats at the Karowe Mine in Botswana. That diamond, one inch long with a sharp boundary between dusky pink and colourless sections, is considered one of the most important pink diamonds in history.
Oded Mansori, co-founder of diamond-cutting firm HB Antwerp, said: 'This stone has the potential to become one of the most important pink diamonds ever polished. Its intensely rich coloration is a testament to the geological uniqueness of the Karowe Mine.'
