The Star of Kashmir: An exceptional sapphire and diamond ring. Photo Christie's Image Ltd 2013

Set with a cushion-shaped sapphire, weighing approximately 19.88 carats, flanked on either side with cushion-shaped diamonds, weighing approximately 3.02 and 2.72 carats, to the graduated diamond line shoulders and engraved sides, mounted in platinum, ring size 5¾. Estimate CHF2,400,000 – CHF2,900,000

Accompanied by report no. 66221 dated 11 December 2012 from the SSEF Swiss Gemmological Institute stating that the sapphire is of Kashmir origin, with no indications of heating, and a Premium Appendix stating that 'A natural Kashmir sapphire of this size and purity is extremely rare and thus, the described gemstone with its combination of outstanding characteristics is a very exceptional treasure.'

Report no. 12105104 dated 29 October 2012 from the Gübelin GemLab stating that the sapphire is of Kashmir origin, with no indications of heating, a Note stating that 'Large sapphires of top gem-quality are true rarities of nature', and an Appendix on 'The Star of Kashmir'

Report no. CS 51069 dated 3 August 2012 from the AGL American Gemological Laboratories stating that the sapphire is of Kashmir origin, with no clarity enhancement, and a JewelFolio on 'The Star of Kashmir' stating that 'Its size, provenance and outstanding quality signifies a gem sapphire of unique rarity'

Report no. 5101844735 dated 10 July 2012 from the GIA Gemological Institute of America stating that the 3.02 carat diamond is G colour, VS1 clarity

Report no.2145736682 dated 28 June 2012 from the GIA Gemological Institute of America stating that the 2.72 carat diamond is G colour, VS2 clarity

Christie's. MAGNIFICENT JEWELS. 15 May 2013. Geneva