An art deco spinel and diamond ring, circa 1935. photo Bonhams

The square-cut spinel, weighing 18.70 carats, to fan-shaped shoulders set with baguette and single-cut diamonds, ring size L½. Estimate: £8,000 - 10,000, US$ 13,000 - 16,000

Accompanied by a certificate from The Gem & Pearl Laboratory stating that the natural spinel is unheated. Certificate number 05323, dated 9th March 2012.

Bonhams.Fine Jewellery, 25 Apr 2012. London, New Bond Street www.bonhams.com