Sotheby's New York describes the diamond as "perfect" and is the only classic emerald-cut white diamond of the highest color and clarity and over 100 carats to come to auction.

Sotheby's says the emerald-cut white diamond was mined in southern Africa and weighed more than 200 carats before it was cut and polished.

The head of the auction house's jewelry department said in a statement, "The color is whiter than white. It is free of any internal imperfections."

The owner wishes to remain anonymous.

In 2010, a 24.78-carat emerald-cut pink stone set a record-breaking $46 million at a Sotheby's auction.