A 100.20 carat flawless diamond is displayed at a media preview for Sotheby's Spring Art Auction on March 25, 2015, in Beverly Hills, California.(AFP)
A rare emerald-cut 100-carat diamond is expected to fetch up to a whopping USD 25 million at an auction in New York.
Sotheby's New York will place the internally flawless diamond up for auction at its Magnificent Jewels sale on April 21.
"In terms of size and general shape, we have compared the diamond to a 9-volt battery," said Gary Schuler, head of Sotheby's jewelry department in New York.
The diamond has no measurable nitrogen impurities; it is one of the largest and rarest such stones in existence, according to Robb Report.
The emerald-cut diamond was originally more than 200 carats when the London jewelry house De Beers sourced it from a mine in southern Africa.
The diamond's current owner - who has chosen to remain anonymous - spent more than a year studying, cutting and polishing the gem to achieve its current state.
It is estimated to fetch USD 19 million to USD 25 million. If sold, it will join just five other diamonds measuring over 100 carats that have ever been sold at auction.
"What makes this stone so striking and rare is the combination of its impressive scale, the elegant shape, and the purity and crispness of the stone," Schuler added.