An amethyst, emerald and diamond bangle bracelet, by David Webb. Photo Christie's Image Ltd 2013

 The carved amethyst hinged bangle designed as two opposing horses, with circular-cut diamond detail and cabochon emerald accents, mounted in 18k gold and platinum, 2½ ins. diameter. Signed David Webb, no. BC33. Estimate:  $90,000 – $120,000

With Certificate of Authenticity from David Webb

Christie's. NEW YORK MAGNIFICENT JEWELS AND THE PRINCIE DIAMOND. 16 April 2013. New York, Rockefeller Plaza.