NEW YORK CITY — A diamond unlike any offered before: a 100.20-carat perfect diamond in a classic emerald-cut, was a show-stopper at Sotheby’s Magnificent Jewels auction on April 21. The 100.20-carat, D color, internally flawless, type IIa stone, a member of an elite group of just five comparable-quality diamonds of more than 100 carats that have ever been sold at auction worldwide, according to the auction house, brought $22.1 million.

Including this sale’s result, only six perfect diamonds weighing more than 100 carats have sold at auction in the last 25 years. Sotheby’s sold five of those – including sales in Geneva, Hong Kong and now New York. Sotheby’s said diamonds of this quality — D color and internally flawless clarity — are incredibly rare and are considered “perfect.” What distinguishes the diamond that sold today within this rarefied league is its beautiful shape: it is the largest perfect diamond with a classic emerald-cut ever to be offered at auction, said the auction house. It is also the first 100-plus-carat perfect diamond sold at auction in North America. The original rough — weighing more than 200 carats — was mined by De Beers in southern Africa. The consignor spent more than one year studying, cutting and polishing the rough diamond to deliver the spectacular stone.