London Sotheby's employee Melica Khanssari, displays a 10.10 carat internally flawless blue diamond in central London, March 15, 2016. The stone, which is the largest oval fancy vivid blue diamond ever to appear at auction, is expected to fetch between $30-35 million at the auction house's Magnificent Jewels and Jadeite auction in Hong Kong on April 5. [Photo/VCG]