The “extremely rare” Kashmir sapphire single-stone ring, weighing 14.3-carats, is cushion-shaped with no indications of heating and has been estimated to sell for between £600,000 and £800,000.
Jean Ghika, head of jewellery at Bonhams UK and Europe, said Kashmir sapphires are amongst the “most highly prized gems for serious collectors”.
“The mines, located high in the Himalayan mountain range in north west India, were only open for a period of approximately 30 years from the late 1880s onwards. Supplies were soon exhausted, making an example of this size a very rare specimen,” she said.
Bonhams will also present a fancy pink-brown diamond ring at the auction. The step-cut diamond weighs 21.33-carats and has also been estimated at £600,000 to £800,000.
Earlier this year Bonhams’ said a surge in demand for coloured gemstones had prompted “rapidly rising prices”, with sapphire seeing a particular rise in popularity especially when it came to wedding and engagement rings.
Meanwhile, a 12.08-carat pear-shaped white diamond single-stone ring – which has been graded by the Gemological Institute of America (GIA) as D colour and VVS1 clarity – has been estimated at £500,000 to £700,000.
Other lots will include animal-themed Cartier jewellery, Van Cleef & Arpels, a rare Bulgari design and three pieces of jewellery created in the Art Deco period featuring emeralds.