What a gem! Star diamond in HK sale

A dazzling pink diamond, described as one of the world's purest, could fetch more than US$21 million (HK$164 million) when it goes on sale in Hong Kong next month, says auction house Sotheby's.

At 11.15 carats, the cushion-shaped gem is called "Williamson Pink Star," in tribute to two other pink diamonds.

One is the "CTF Pink Star", a 59.60-carat oval mixed-cut diamond which sold for a record US$71.2 million in 2017.

The other is the Williamson stone, a 23.60 carat diamond given to Britain's Queen Elizabeth as a wedding gift by Canadian geologist John Thorburn Williamson. Worn by the monarch in a Cartier brooch, it was discovered in his mine in Tanzania.

The "Williamson Pink Star" also originates from that mine.

"Pink diamonds are exceptionally rare in nature," said Kristian Spofforth, Sotheby's head of jewelry.

Top-quality colored stones are prized by the super wealthy and Spofforth said he expected many bids on October 5.

The "Williamson Pink Star" will go on tour to Dubai, Singapore and Taipei first.