The necklace features 178 diamonds in total and was expected to hit the block in New York at Guernsey’s auction house on 27 June.
Guernsey's recently uploaded a message to its website that reads: "Princess Diana's Swan Lake Suite has been privately sold to a prominent museum. Accordingly, our auction of the beautiful jewels has been cancelled."
The platinum necklace is mounted with brilliant-cut diamonds in a scroll motif. Suspended from the necklace are five cultured South Sea pearls and seven marquise diamonds.
The piece was created by former British Crown Jeweller Garrard. Princess Diana wore the necklace in June of 1997 at the gala opening of the Swan Lake ballet at London’s Royal Albert Hall, just months before her untimely death in Paris.
The collection was expected to return up to $US15 million ($AU22.1 million) at auction.
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