A model holds "The Sun-Drop Diamond" during a press preview of Sotheby's auction on November 9, 2011 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 November 15, 2011 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". AFP PHOTO / FABRICE COFFRINI (Photo credit should read FABRICE COFFRINI/AFP via Getty Images)