A 118.28-CARAT white diamond broke a world record on Monday when it fetched HK$238.68 million (S$38.4 million) at a Hong Kong auction.
The sparkling translucent stone was sold to an unnamed phone bidder, described as a private collector, at the Sotheby's auction following bidding that lasted more than six minutes.
Mr Quek Chin Yeow, deputy chairman of Sotheby's Asia, said the sale signalled a "moving trend" for the southern Chinese city to host major global auctions.
Hong Kong has become a centre for jewellery auctions, thanks to growing wealth in China and other parts of the region.
"The downturn everybody thinks is happening in Asia, or the slowdown... a lot of the collectors are still extremely wealthy individuals," he said.
The egg-shaped stone sold on Monday has been described as the finest of its kind to appear at an auction. Earlier estimates valued it at US$28 million (S$35 million) to US$35 million.
The stone, dubbed the Magnificent Oval Diamond, was discovered in a deep mine in an undisclosed southern African country in 2011. Before being cut, it weighed 299 carats.
The stone, described by Sotheby's as "the largest D- colour flawless diamond" sold at auction, has been given the highest quality rating awarded by the Gemological Institute of America. "D colour" diamonds are rare and colourless and fetch premium prices.
The sale beat the record set at a diamond auction last year, when a 101.73-carat diamond was sold for US$26.7 million (about S$33.3 million).