The stone, of a "vivid pink" hue and considered near perfect, but not quite flawless, triggered brisk bidding in Christie's autumn sales of Asian and Chinese art in Hong Kong.
The earlier record was, set 15 years ago at Geneva for a 19.66-carat stone that was sold for $7.4 million. The pink gem's per-carat price of $2.2 million was also the highest cost for any diamond at auction.
The stone, set in a so-called "cushion-cut" ring by famed jewelers Graff Diamonds, was just a quarter the size of the Geneva stone and not quite flawless but the stone's "vivid pink" is considered near perfect.
While the South African-mined diamond isn't quite rated flawless given minor blemishes, Christie's said that these could be removed by minor repolishing.
Christie's has a track-record of putting rare polished stones up for sale in Asia, given its confidence in the depth of the Asian market for the world's top gemstones and artwork.
Last May, before the financial crisis began to hurt the global auction market, Christie's sold a squash-ball-sized, 101.27-carat diamond in Hong Kong for $6.2 million.
Despite this, some major gems have disappointed in Asia, including a 72.22-carat "D" flawless white diamond that failed to hit its reserve price in a Sotheby's Hong Kong sale last April, falling short of its $10-12 million pre-sale estimate.
