The world's largest white diamond will be auctioned on May 11

The world's largest white diamond for sale will go up for auction on May 11 in Geneva.

According to a British auction company, The Rock is estimated to be worth between $20 million and $30 million, making it the largest diamond auctioned in its two-and-a-half-century history.

The 228-carat diamond was found in a mine in South Africa 20 years ago, and another 205-carat diamond will be put up for auction, which was found in South Africa 121 years ago today.