A rare, 5-carat pink diamond will be sold in Hong Kong this December by Christie's, which expects the stone to hover near world record prices, thanks in part to the buying prowess of top Asian jewellery collectors.

The stone, set in a so-called "cushion-cut" ring by famed jewellers Graff Diamonds, is expected to fetch between $5-$7 million, in reach of the current world auction record for a pink diamond -- a 19.66-carat stone that sold in Geneva for $7.4 million in 1994.

While just a quarter the size of the record-holding pink gem and not quite flawless, the stone's "vivid pink" is considered near perfect and the auction house has touted it as one of the best coloured stones to appear in recent years.

"There are pink diamonds and then there are pink diamonds," said Francois Curiel, the international head of Christie's jewellery department. "It is extremely rare for a stone of such top quality to appear on the market with top notes in colour, cut, clarity and carat weight. This 5-carat vivid pink gem combines the best of all criteria," Curiel added.

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 bite the global auction market, Christie's sold a squash-ball-sized, 101.27-carat diamond in Hong Kong for $6.2 million.

"Asian collectors rank among our most important group of buyers ... Hong Kong is firmly alongside New York and Geneva as a top centre for the best jewels," said Kate Malin, a spokeswoman for Christie's in Asia.

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.

While the world's most expensive jewel ever sold at auction is the "Wittelsbach" blue diamond, a 17th-century deep greyish-blue stone that fetched $24 million last year, top red and pink gemstones are also known for stratospheric valuations.

"In the fascinating realm of natural colour diamonds, those of a distinct pink hue are among the rarest and most sought after," Christie's said.