Sotheby’s auction house will be offering an 88.22-carat, flawless diamond as the top lot of its Hong Kong Sale of Magnificent Jewels and Jadeite on April 2. The D color, flawless, type Ila, oval brilliant gem has an estimate of $11.2 million to $12.7 million.

The auction house is calling the stone “perfect” based on “every critical criterion” that diamonds are measured. It has received the highest ranking for color, clarity, cut, polish and symmetry. There are few diamonds ever offered at auction of more than 50 carats that have all of these qualities. In fact, it is one of only three oval diamonds of over 50 carats to appear at auction in living memory, and the largest to be auctioned in over five years, Sotheby’s said in a statement. The Type IIa designation means it is the most chemically pure type of diamond with exceptional optical transparency. It comprises fewer than 2% of all gem diamonds.

The finished diamond was from a 242-carat rough stone that was discovered in the Jwaneng mine in Botswana, jointly owned by De Beers and the government of Botswana and known for producing high quality roughs. Following its discovery, the rough was cut and polished over a period of several months to produce a symmetrical oval brilliant diamond. Sotheby’s said given the elongated shape of the rough the oval shape was chosen to preserve the greatest amount of weight.

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“When you think that one ton of mined earth yields less than a carat of diamond, and that high quality diamonds over 10 carats are a rarity, the discovery of a 242-carat rough, of gem quality and exceptional size, is nothing short of a miracle,” said Patti Wong, chairman of Sotheby’s Asia. “The perfect 88.22-carat diamond is a summary of everything: a wonder of nature, a masterpiece resulting from man’s ability to shape the hardest material on earth into an object of ultimate beauty and the most concentrated form of wealth.”