The largest white diamond to come to auction will appear at Christie’s in Geneva on May 11. The 228-carat, pear-shaped diamond has an estimate of $20m to $30m. The stone was mined about 20 years ago in South Africa. The VS1, G color diamond was formerly known as the Harrods Diamond. After making its debut in Dubai, ‘The Rock’ will travel to Taipei, New York and Geneva, where it will be auctioned on May 11.