A sapphire and diamond ring. Photo Christie's Image Ltd 2014

Set with a cushion-shaped sapphire, weighing approximately 20.20 carats, to the shield-shaped diamond shoulders, mounted in platinum, ring size 4¾. Estimate CHF420,000 – CHF580,000 ($481,907 - $665,490)

Accompanied by report no. 14030180 dated 24 March 2014 from the Gübelin Gemlab stating that the sapphire is of Kashmir origin, with no indications of heating, and an Information Sheet on Unheated sapphires

Report no. 71208 dated 25 September 2013 from the SSEF Swiss Gemmological Institute stating that the sapphire is of Kashmir origin, with no indications of heating

Report no. 6155943391 dated 12 September 2013 from the GIA Gemological Institute of America stating that the sapphire is of Kashmir origin, with no indications of heating

Christie's. GENEVA MAGNIFICENT JEWELS. 14 May 2014, Geneva -http://www.christies.com/