The De Beers Millennium Jewel 4 sold for $31.9m at Sotheby's Hong Kong on April 5.

At 10.10 carats, the diamond is the largest fancy vivid oval blue diamond ever offered at auction.

The De Beers Millennium Jewels were the subject of an attempted heist in 2000

It's officially the most valuable gem ever sold in an Asian auction and indicates the health of the Asian market despite recent economic turbulence.  

The Millennium Jewel collection was unveiled at the Millennium Dome in London in 2000.

It was the target of a high-profile heist shortly before the opening ceremony, which was foiled by police.

Tom Moses, executive vice president of the Gemological Institute of America (GIA), explained why blue diamonds are so highly prized: "Blue diamonds of any intensity of colour are amongst the rarest of all gems.

"Highly saturated blue diamonds over ten carats combined with an Internally Flawless clarity grade are extremely rare.

"There have been fewer and fewer new rough diamonds discovered over the last decade that produce this colour.

"Most of the recent diamonds offered for sale in this category are coming from private collections—not diamond mines."

The record for any diamond remains $48.4m, set for the Blue Moon of Josephine at Sotheby's in 2015.

A number of blue diamonds are being traded this year, with the Oppenheimer Blue to be sold in May and an important ring belonging to Shirley Temple offered on April 19.

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