(IDEX Online) - A Graff necklace featuring a 13.88-carat Columbian emerald sold for just over $575,000 at Bonhams, London - more than five times its pre-sale estimate. It was the top selling piece in the London Jewels auction of over 200 lots, including many 18th- and 19th-century antiques, as well as art deco items.The detachable pear-shaped emerald drop (pictured) is suspended from a series of pear-shaped diamonds, graduating in size towards the centre, with a total weight of 32.70 carats.Reports from Gubelin said the emerald had moderate clarity enhancement (oil and resin) and had a gemstone rating of 88.1 (excellent).