Christie’s has sold the ‘Pink Legacy’ diamond at auction in Switzerland for more than $US50 million ($A69 million) including fees, saying it’s a new world record price per carat for a pink diamond.

Christie’s said that renowned jeweller Harry Winston was the buyer.

The auction house had expected to fetch $US30-50 million ($42-69 million) for the nearly 19-carat, rectangular-cut stone, the largest fancy vivid pink diamond that it has ever put under the hammer.

It was the standout offering on Tuesday at Christie’s autumn jewellery auction in Geneva, Switzerland.

#AuctionUpdate THE WINSTON PINK LEGACY realises $50,375,000, achieving a #WorldAuctionRecord price per carat for a pink #diamond https://t.co/YGqE9riTel pic.twitter.com/CmKZ2Ds9s2

— Christie's (@ChristiesInc) November 14, 2018

The standing room-only ballroom broke into applause after the auctioneer struck down a hammer price of $US44.5 million ($61.8 million). That excludes the standard “buyer’s premium” and other fees.

The stone once belonged to the Oppenheimer diamond family, and Christie’s says it’s among the most chemically pure gems.