Famous Diamonds: The Incomparable Diamond

Famous Diamonds: The Incomparable Diamond

The phrase ‘diamond in the rough’ perfectly describes the Incomparable Diamond. This diamond’s more than three decades of existence has seen it come from a small town in Congo and move across continents before it was lost to the world. Let’s delve a bit more into this beautiful gem’s long history, including where it rests today.


Origins of The Incomparable Diamond

The Incomparable Diamond has one of the most incredible origin stories. The stone would have been lost to the world if not for a little African girl. In 1984, she was rooting through dirt piled in front of her uncle’s house. The pile had been mined from the nearby MIBA Diamond Mine located in Mbuji Mayi, a small village in the Democratic Republic of Congo. The miners had discarded the pile, regarding it as being too bulky to yield anything precious. However, the girl found a huge rock that she brought to her uncle for inspection.



The stone was irregularly shaped, rough, and yellow. The surface had dents and pits, together with cavities and multiple cracks. The uncle, however, knew that it was a diamond and sold it to some local diamond traders. These traders sold it to some Lebanese dealers in Kinshasa, who transported it to Europe where it caught the eye of a De Beers Company buyer in Antwerp.

After the purchase, Sir Philip Oppenheimer, a Director at the De Beers Company, sold it to a team led by Donald Zale of the Zale Corporation located in Dallas, Texas. Together with his partners, they unveiled the big stone at the 75th Anniversary of the Corporation. Afterwards, the rough stone was displayed at the Smithsonian Institute in the Natural History section.


Making The Incomparable Diamond

Marvin Samuels, one Donald Zale’s business partners and part owner of the stone, took up the job of cutting it. Backed by a team of expert cutters, he examined the stone for 4 whole years. This examination included making a “cutting window,” cutting into the interior of a diamond for the purpose of exploring its structure. They found that, while the outside was filled with pits and cavities, the inside was almost completely free of imperfections.

The team then needed to decide how exactly they would cut the stone. With minimal cutting, they could create a 531 carat diamond that would bypass the 530 carat Cullinan I in size. However, with more cutting, they could create a stunningly clear, virtually flawless diamond.



Eventually, Samuels’ team decided that perfection was a much more worthy endeavor than size. The stone yielded one big diamond and 14 fragments.  Further examinations of the fragments showed that not all were the deep yellow of the uncut stone: some had a brown cast, others were a paler yellow, while others were practically colorless.

Each of these fragments were faceted to make beautiful final pieces, the largest being 15.66 carats and the smallest only weighing 1.33 carats.


The 15th and largest piece was cut and graded as a Shield-Shaped Step Cut, Fancy Brownish-Yellow 407.48 carat gem. The Incomparable Diamond is the third largest in existence after the Golden Jubilee and Cullinan I diamonds. It is also the largest diamond to be graded as Internally Flawless.

The lead cutter, Marvin Samuels, coined the term “triolette” to explain its unique triangular shape.


The Incomparable Diamond Today

While initially known as the Golden Giant, the stone had been renamed as the Incomparable Diamond when it was put up for auction in October 1988 at $20 million. The highest bid was from a Theodore Horovitz at $12 million. Since it did not fetch the intended amount, the Incomparable was removed from auction.



A similar-looking stone was placed for auction on Ebay in November 2002. The opening bid was set at $15 million, making it the largest stone to ever be put up for bidding on the internet. When nobody was able to match the price, the auction was closed, and the stone disappeared from the public.

The last the public saw of this diamond was in 2013 when it went on sale at the Singapore JewelFest. It was set as a pendant in the L’Incomparable, the priciest necklace in the world according to the Guinness World Record. The necklace was going for $55 million and attracted a lot of attention from Asian and European buyers.


Diamonds carry a lot of history. Read more stories about the most famous diamonds of all time.

Famous Diamonds: The Golden Jubilee

Famous Diamonds: Cullinan I & II



About The Author


Debbie Azar is the Co-Founder and President of Gemological Science International (GSI), one of the largest gemological organizations in the world, and a distinguished leader in the global diamond and jewelry industry. As an executive with extensive knowledge of the jewelry and gem lab industries, her entrepreneurial skills and vision have helped GSI achieve rapid and continuous growth worldwide, establishing 13 leading-edge gemological facilities on four continents. She currently serves on the boards of the Jewelers Vigilance Committee, Responsible Jewellery Council, and Jewelers for Children, and is a member of the 24 Karat Club of New York. She has been featured in Forbes, Daily Mail, Good Morning America, Bloomberg, Bloomberg Businessweek, Fox Business, Fox5, CBS2, BOLDTV, Varney&Co, The Street, and NASDAQ, among others.

Debbie Azar

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