The price smashed the previous Guinness world record, set 15 years ago in Geneva for a 19.66-carat stone that sold for $7.4 million. The pink gem's per-carat price of $2.2 million was also the highest ever paid for any diamond at auction, Christie's said.

"No stone has ever been sold for $2 million a carat, we were used to ... a million dollars a carat for colored diamonds but never 2 million," said Francois Curiel, Christie's Europe chairman. "This is an absolute record that is not going to be broken for a while I believe."

"Vivid Pink," as it's called, is a glittering five-carat stone flanked by two white diamonds and set in a ring by elite jeweler Graff, owned by U.K. billionaire Laurence Graff. Demand exceeded Christie's' expectations. Last week the auction house's department head for jewels, Vickie Sek, predicted the rock would fetch $8 million.

Auctioneer Francois Curiel said the pink gem's per-carat price of $2.2m was also the highest ever paid for any diamond at auction. The Most Expensive Diamond toured Singapore, Bangkok, Geneva and Taipei before returning to Hong Kong, where collectors and connoisseurs vied for it at the Convention and Exhibition Center.

An anonymous Asian buyer placed the winning bid of $83.5 million Hong Kong dollars via telephone through a Christie's representative, beating out Shanghai millionaire Liu Yiqian, who ranks 196th on Forbes' list of the richest people in mainland.