100-carat classic emerald-cut diamond coming to auction

An auction house worker holds a 100.20-carat diamond as she poses for photographers in central London, on Friday.

A “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. It’s an internally flawless D colour stone, which the auctioneer said is considered “perfect”.

Sotheby’s New York jewellery department head Gary Schuler likened the 100.20-carat stone’s transparency “to a pool of icy water”.

The stone is the only classic emerald-cut white diamond of the highest colour and clarity and over 100 carats to come to auction, according to Sotheby’s.

The diamond was mined in southern Africa within the last 10 years and weighed over 200 carats before it was cut and polished, the auction house said.

Watch video: Sotheby's unveils 100-Carat perfect diamond

The owner wishes to remain anonymous.

Only five “perfect” diamonds over 100 carats have sold at auction in the last 25 years. A 118-carat oval-cut stone fetched $30.6 million at Sotheby’s in 2013, setting a record for a white diamond.

A record for any diamond is $46 million for a 24.78-carat emerald-cut pink stone, set at Sotheby’s in 2010. It also set a record for any jewel at auction.