FILE -In this April 30, 2013 file picture a Christie's employee displays the largest colour flawless diamond, weighing 101.73 carats, during a preview at Christie's auction house in Geneva, Switzerland,. The largest pear-shaped colour flawless diamond is expected to reach US $ 30 million and it will be the hightlight at the Christie's auction on Wednesday May 15 , 2013 in Geneva. (AP Photo/keystone, Salvatore Di Nolfi,File)