HONG KONG (AFP) - An enormous oval-shaped diamond named the "Pink Promise" is set to be auctioned at Christie's in Hong Kong, with an eye-watering US$42 million (S$57.15 million) price tag.
A 14.93-carat pink gemstone forms the centre-piece of the diamond-studded ring.
A Christie's spokesman said it was one of the most important pink diamonds ever to be sold because of its colour and clarity.
"The rarity of pink diamond makes it so valuable," Mr Fung Chiang of Christie's jewellery department said.
"For diamond production every year, we are talking about less than two per cent (for) coloured diamonds," Mr Chiang said, adding that not every piece shares the same "beautiful" colour.
Researchers still do not fully understand the "exact structural defect" that causes the appealing pink hues, the auction house added in a statement on Wednesday (Nov 1).
The ring will go under the hammer on Nov 28 in Hong Kong.
An ongoing anti-corruption drive in mainland China has done little to dent feverish bidding in Hong Kong's auction houses.
A 1,000-year-old bowl from China's Song Dynasty sold at auction house Sotheby's to an anonymous bidder for US$37.7 million in the city last month, breaking the record for Chinese ceramics.
The small piece - which dates from 960-1127 - broke the previous record of US$36.05 million set in 2014 for a Ming Dynasty wine cup which was snapped up by a Shanghai tycoon famous for making eye-watering bids.
Earlier this year, a giant diamond named the "Pink Star" broke the world record for a gemstone sold at auction when it fetched US$71.2 million at Sotheby's.
The 59.60-carat rock was sold to the city's Chow Tai Fook jewellery chain, which has a strong presence across East Asia.
Hong Kong tycoon Joseph Lau, who was convicted of bribery in Macau in 2015, made waves that year when he spent US$48.4 million on a 12.03-carat diamond for his then-seven-year-old daughter at Sotheby's in Geneva.
The purchase came a day after he scooped up a 16.08-carat pink diamond for a comparatively modest US$28.5 million at Christie's.