An exceptional emerald and diamond ring. Photo Christie's Image Ltd 2013

Set with a cushion-shaped emerald, weighing approximately 23.28 carats, to the diamond line shoulders, mounted in platinum, ring size 6. Estimate CHF1,200,000 – CHF1,700,000

Accompanied by report and note no. 12075152 dated 30 July 2012 from the Gübelin GemLab stating that the emerald is of Colombian origin, with no indications of clarity enhancement

Report no. 23891 dated 25 June 2012 from the SSEF Swiss Gemmological Institute stating that the emerald is of Colombian origin, with no indications of clarity modification, and an Appendix letter indicating that 'A natural emerald from Colombia of this size and quality is very rare and exceptional.'

Report no. cs50148 dated 13 June 2012 from the AGL American Gemological Laboratories stating that the emerald is of Colombian origin, with no indications of clarity enhancement, a letter indicating that 'this fine emerald possesses a high clarity that provides a superior degree of transparency', and a JewelFolio

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