A model holds ‘The Sun-Drop Diamond’ during a press preview of Sotheby’s auction yesterday in Geneva. One of the world’s largest diamonds, a pear-shaped 110.3-carat yellow rock, will go under the hammer in Geneva on Tuesday expecting to fetch about $15 million. The Sun-Drop diamond, discovered in South Africa last year, is billed by Sotheby’s as the “world’s largest known pear-shaped fancy vivid yellow diamond”.