The De Beers Millennium Jewel 4 will cross the block at Sotheby's Hong Kong on April 5.
The lot is the largest oval fancy vivid blue diamond ever offered at auction and is valued at $30m-35m.
 The De Beers Millennium Jewel 4 is one of a set of 12 |
Tom Moses, executive vice president and chief research and laboratory officer of the Gemological Institute of America (GIA), explained: "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 is $48m, set for another flawless blue stone (the Blue Moon of Josephine) at Sotheby's last year.
The present lot is one of 12 stones that make up the De Beers Millennium Jewel Collection, which was unveiled at London's Millennium Dome in 2000.
The collection was the target of a heist on November 17, 2000 that was foiled by officers from the Metropolitan Police's Flying Squad.
Queek Chin Yeow, Sotheby's deputy chairman in Asia, comments: "This beautiful blue stone combining Nature's rare beauty, superlative colour, unusual shape and illustrious provenance offers yet another wonderful collecting opportunity for connoisseurs worldwide."
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