The star of Sotheby’s auction of Magnificent Jewels and Noble Jewels in Geneva this month will be a Cartier ring set with an extremely rare fancy vivid blue diamond. The 8.01ct diamond is called the Sky Blue Diamond. Its hue is highly sough after.

The presale estimated price of this ring is US$15 million to US$25 million. The blue diamond has an exceptional colour – a wonderfully clear celestial blue – and an elegant square emerald cut. It is sure to captivate collectors of rare gemstones.

Sotheby’s previously auctioned the Blue Moon of Josephine, which sold for US$48.5 million. It is a cushion-shaped 12.03ct fancy vivid blue internally flawless diamond.