A pink diamond the size of a postage stamp is going on the auction block, and it's estimated to bring as much as $28 million.
The 16.08-carat gem is poised to set a record for a cushion-shaped fancy vivid pink diamond when Christie's offers it at its Magnificent Jewels sale in Geneva on Nov. 10.
The auction house said it is the largest diamond of its kind to come to auction.
The fancy vivid pink grading means the hue is of the purest and strongest saturation, said Rahul Kadakia, Christie's head of jewelry. The color is even and shows no trace of a secondary color that may include purple, orange brown or grey in pink diamonds of a lower grade.
"For a savvy diamond investor, it's a great price," he said of the pre-sale estimate of $23 million to $28 million.
Christie's described the seller as a U.S. client who purchased it about 10 years ago as an investment.
A smaller, 8.72-carat pink diamond of the same shape and fancy vivid pink grade sold for $15.9 million at a Sotheby's auction in Geneva in May.
A slightly lower-grade fancy intense cushion-shaped pink diamond of 34.65 carats known as The Princie brought $39.3 million at Christie's in 2013.
The diamond in the November sale is set as a ring with a double row of white diamonds and a third row of small pink diamonds enveloping the large stone. The band consists of small circular-cut white diamonds set in platinum.
The per-carat auction record for any pink diamond is $2.1 million per carat set for a cushion-shaped stone of 5 carats named The Vivid Pink.
"The 2009 diamond readjusted the bar for pink diamonds," Kadakia said.
The winning bidder in November will have naming rights for the gem.
The stone will go on a multi-city tour starting Saturday. The first stop is Hong Kong (Oct. 2-4) followed by New York (Oct. 16-19) and London (Oct. 26-27). In Geneva it will be on view Nov. 6-Nov. 10.
A 24.78-carat emerald-cut pink diamond holds the auction record for any diamond. It sold for $46 million at Sotheby's in 2010.