The Incomparable was found in its rough state weighing 890 carats and in the town of Mbuji Mayi in the Democratic Republic of Congo (formerly Zaire) in the 1980s. It was found by a young girl playing in a pile of rubble outside her uncle's house. This rubble had been legitimately collected from old mine dumps from the nearby MIBA Diamond Mine, having been rejected during the recovery process as being too bulky to be worth scanning for diamonds. The girl gave the diamond to her uncle, who sold it to some local African diamond dealers and a group of Lebanese buyers operating out of Kinshasa.
It was later purchased in Antwerp by the Senior De Beers Buyer. As a result, Sir Philip Oppenheimer, then president of the Central Selling Organization and a De Beers director, sold it to Donald Zale, chairman of the board of the Zale Corporation, the Dallas-based jewelry store chain. He bought the diamond in partnership with Marvin Samuels, of the Premier Gems Corporation, and Louis Glick, both prominent figures in the New York diamond industry.
The job of overseeing the cutting was given to Mr. Samuels, renowned for his experience and expertise in the faceting of large diamonds. This diamond showed its fair share of problems; four years were spent studying and cutting the stone. The Incomparable was the largest gem cut from this stone, and was graded as a Shield-Shaped Step cut, 407.48-carat, fancy brownish-yellow, internally flawless diamond. It is the third largest diamond ever cut, after the Golden Jubilee and the Cullinan I, and measures 53.90 x 35.19 x 28.18 mm. Its unusual triangular shape elicited a new imaginary term from Marvin Samuels - a "triolette."
The huge stone was finally unveiled in November, 1984, . Shortly afterwards, it was displayed at the Natural History wing of the Smithsonian Institute in Washington DC.
The Incomparable was unveiled on November 1984, which coincided with the Zale Corporation's 75th anniversary (their Diamond Anniversary)Shortly afterwards it was put on display at the Natural History wing of the Smithsonian Institute in Washington DC. When it was auctioned in New York in 1988, it was the largest diamond ever offered to the public for sale. It was withdrawn after not reaching its $20 million reserve price, and was again withdrawn from sale for the same reason in November 2002, this time on eBay. Louis Glick is said to own the stone still today.