Rare Bulgari blue diamond worn by Priyanka Chopra Jonas to be auctioned

The Bulgari Laguna Blu, an 11.16-carat fancy vivid blue gem, is expected to fetch more than $25m

Indian actress Priyanka Chopra Jonas arrives at the Met Gala on May 1 wearing the diamond, alongside her husband Nick Jonas. AFP

An exceptionally rare diamond worn by Indian actress Priyanka Chopra Jonas to Met Gala is to go on show in Geneva this week before being auctioned on May 16.

The Bulgari Laguna Blu, an 11.16-carat fancy vivid blue diamond, is expected to fetch more than $25 million at Sotheby’s Geneva Luxury Week.

The gem has been in the same European collection since it was made in 1970 and this is the first time it has been offered for sale.

Initially mounted as a ring by Bulgari for a special commission with a pear-shaped stone, it is only the third fancy vivid blue diamond to come to auction.

Blue diamonds, among the rarest of all coloured varieties of the precious gemstones, are an accident of nature produced by the presence of the trace element boron within the diamond’s carbon structure during its formation deep in the earth’s core.

But fancy blue diamonds - so called because they have the brightest hue a diamond can display - larger than 10 carats are the most precious.

Fewer than 10 of that size have come to auction in the past few decades, four of which were sold by Sotheby’s.

The earliest and one of the largest blues was the Hope diamond, a 45.52 carat gem discovered in India in the 17th century, which was stolen at least twice and was said to bring bad luck to whoever owned it.

Blue diamonds have also been mined at the Cullinan mine in South Africa, where the largest gem in Britain's Imperial State Crown was discovered.

The Bulgari Laguna Blu is said to be the most valuable piece sold by Bulgari.

Olivier Wagner, head of jewellery at Sotheby’s Geneva, said it was extraordinary in “every way”.

“At 11.16 carat, this unmodified pear-shaped blue diamond has received the highest grade for a blue diamond by the Gemological Institute of America, acknowledging its mesmerising colour and hue.

“This true wonder of nature was selected by Bulgari, the prestigious Roman Jewellery Maison, over 50 years ago, to create a ring for a discerning private collector who has kept it ever since.

“The Bulgari Laguna Blu diamond is bound to become the object of any collector’s dream.”

The stone, which is set in a necklace inspired by Rome, the ancient birthplace of Bulgari, was worn at the Met Gala by Ms Chopra Jonas, who is a global ambassador for the fashion house.

Its shape pays homage to the Italian capital, with its interlocking diamonds set in a pattern inspired by the bay laurel wreaths worn by Greco-Roman emperors.

Rebecca Corbin-Murray, a stylist who collaborated with Ms Chopra Jonas on her Met Gala look and chose the piece for its extraordinary colour, said: “Absolutely enchanting to behold, the Bulgari Laguna Blu captures the essence of Bulgari’s exuberant style, a legacy that has been interwoven with Hollywood glamour since the 1950s. It also nods to Bulgari’s birthplace of Rome, capturing the brand’s ancient heritage in the most modern way."

The actress wore the necklace again days later at a screening of her new romantic comedy Love Again, which she attended with her husband Nick Jonas, the American singer-songwriter.

The Bulgari Laguna Blu diamond will be exhibited at the Mandarin Oriental in Geneva from Friday, before the auction at Sotheby’s in the city, with bidding open until May 16.