A sapphire and diamond necklace, by Van Cleef & Arpels. Estimate $130,000 – $180,000. Photo Christie's Image Ltd 2015

Designed as a graduated series of eight oval-cut sapphires and circular-cut diamond clusters, centering upon a detachable cushion-cut sapphire, to the circular-cut diamond surround, spaced by marquise and circular-cut diamond links to the circular-cut diamond backchain, 16 1/2 ins. (may also be worn as a bracelet), with French assay marks for platinum and 18k gold. Signed Van Cleef & Arpels, nos. 91601 (backchain) and 91602 (pendant)

Accompanied by report no. CS 69109 dated 28 July 2015 from the AGL American Gemological Laboratories stating that it is the opinion of the Laboratory that the origin of these sapphires would be classified as Cambodia (one sapphire), Ceylon (Sri Lanka, one sapphire) and Burma (Myanmar, six sapphires), with no gemological evidence of heat. Clarity enhancement: none

Christie's. IMPORTANT JEWELS, 20 October 2015, New York, Rockefeller Plaza