A Sotheby's employee poses for pictures with the "Graff Vivid Yellow," at 100.09 carats one of the rarest yellow diamonds of its size, in central London on April 11, 2014, ahead of the forthcoming New York auctions of contemporary, impressionist and modern art. The diamond is expected to fetch 25million US dollars at the May 13 Sotheby Spring Magnificent Jewels and Nobel Jewels auction. Industry experts believe the yellow diamond could sell for as much as $25 million at the May 13th auction. The stones colouring is considered to be similar to that of a daffodil and is among the largest vivid yellow diamonds in the world. The diamond, which weighed in at 190 carats in the rough, was originally named the Dream Diamond. Graff bought that stone in 2005 in Kimberley, South Africa and had it cut and polished and then changed to its current name. AFP PHOTO/ANDREW COWIE         (Photo credit should read ANDREW COWIE/AFP/Getty Images)