A “perfect” 100-carat diamond in a classic emerald cut has sold for just over $22m (£15m) at auction in New York.

The internally flawless D colour 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 final price on Tuesday night was $22,090,000, including the buyer’s premium.

“This 100.20-carat diamond is the definition of perfection. The colour is whiter than white. It is free of any internal imperfections,” Sotheby’s New York jewellery department head, Gary Schuler, said before the sale, likening its transparency “to a pool of icy water”.

The pre-sale estimate had been $19m-$25m.

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

The seller wished to remain anonymous. The buyer was also anonymous, and the winning bid came in by phone.

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

The record for any jewel is $46m for a 24.78-carat emerald-cut pink diamond, set at Sotheby’s in 2010.