A 100-carat emerald-cut diamond is on display at Sotheby's, Friday, April 17, 2015, in New York. The "perfect" 100-carat diamond in a classic emerald cut is going on the auction block, where it could fetch between $19 million to $25 million. Sotheby's will offer the white diamond on April 21, in New York. (AP Photo/Mary Altaffer)

A 100-carat emerald-cut diamond is on display at Sotheby’s, Friday, April 17, 2015, in New York. The “perfect” 100-carat diamond in a classic emerald cut is going on the auction block, where it could fetch between $19 million to $25 million. Sotheby’s will offer the white diamond on April 21, in New York. (AP Photo/Mary Altaffer)