The Incomparable Diamond

The Largest Yellow Diamond In The World

The Incomparable Diamond takes its place in the world as one of the largest and most breathtaking diamonds in existence. With its impressive weight of 407.78-carats, it is the fourth biggest gem-quality rough stone to ever be discovered! It is preceded only by the Cullinan, the Excelsior, and the Star of Sierra Leone diamonds in sheer size. However, it is the largest yellow diamond in the world! Ironically, the Incomparable is also the only gemstone of its caliber known to have been offered at an online auction – on the eBay website.

If you’d like to learn more about the Incomparable Diamond, in this article you will find:

The Incomparable Diamond in the hand of Leo Wins, master diamond cutter.
The Incomparable Diamond in the hand of Leo Wins, master diamond cutter.
Discovered in
Country of Origin
Democratic Republic of Congo (formerly Zaire)
Mine of Origin
Mbuji Mayi, operated by Société minière de Bakwanga (MIBA)
Carat Weight
407.78 carats
Cut Shape
Shield-shaped step cut (triolette shape)
Internally Flawless (IF)
Fancy Deep Brownish Yellow (with color variation)
Previous Owners
  • Local African diamond dealers
  • Lebanese buyers from Kinshasa
  • De Beers Company
Current Owner
Likely the group of three gentlemen (Zale, Glick, Samuels) who purchased it in the 1980s
Estimated Value
Unknown (not sold at auction, rumored starting price $15-20 million)

The Origins of the Incomparable Diamond

The Incomparable Diamond was unearthed in the 1980s in the Democratic Republic of Congo (formerly known as Zaire) in the town of Mbuji Mayi, where the Congolese diamond Societé minière de Bakwanga (MIBA) operates. When diamonds are mined a lot of stones are rejected during the process; for instance, the workers may take into account factors such as the look of the stone and its weight for these decisions. It is clear that these miners are not trained gemologists, and so, there may be thousands of potential fortunes waiting to be discovered in old mine dumps. For every single genuine gemstone that surfaces, there are hundreds of plain ones that are discarded. This is how the Incomparable Diamond’s origin story begins.

A little girl discovers the Incomparable Diamond

A young girl from Mbuji Mayi was playing in her uncle’s yard in a pile of rubble. The rubble had come from one of MIBA’s mine dumps. One of the stones the girl was playing with seemed different and shortly after finding it, the child gave the piece of wreckage to her uncle who suspected he had a fortune in his hands. It was true, he had a diamond in his hands! He went on to sell it to local African diamond dealers who then sold it to a group of Lebanese buyers from Kinshasa.

The Cutting of the Incomparable Diamond

In the 1980s, innovations had come to the diamond-cutting industry. New techniques allowed for more precision during the cutting process. The owners of the Incomparable Diamond were in no rush to make a decision. 

The analysis of the Incomparable Diamond reveals several issues

Several years were dedicated to thorough analysis. The stone was 890 carats in its rough form and so, it took a whole team of highly experienced diamond cutters to do the work as a team, led by Marvin Samuels. The analysis the team performed revealed a few issues with the stone. 

For one, It was narrow in one end, broad in the other, and had a rough, uneven surface. There were bumps and crevices all over it, including cracks and cavities. After detecting these imperfections the team decided to have a look inside the gem to make sure its interior was free of inclusions, which could cause a disaster, if not taken into account during the cutting. A small incision was made on one side of the diamond to complete the study, which resulted in the stone being inclusion-free on the inside.

The Incomparable Diamond is cut down to a 407.78-carats

The team was debating on how to manage some of the stone’s intrinsic imperfections, if done correctly, this meant they could create the world’s largest cut diamond. There was talk among them about making the final jewel bigger than the Cullinan I Diamond (530.2 carats). In the end, however, they decided it would be best to cut the rough stone into one main diamond of high clarity and 14 smaller stones. The main gem’s weight is 407.78-carats and has retained the name ‘The Incomparable Diamond’. The largest of the 14 was cut in a kite shape and weighed 15.66 carats. The remaining smaller diamonds had different sizes and shapes, varying from 1.33-6.01 carats. The rough stone had a yellow-brownish color, however, the 15 stones that were produced from it varied in color! Some of them are the same yellow-brown tint but some of them are nearly colorless.

The Modern Ownership History of the Incomparable Diamond

After the Incomparable Diamond was discovered in the Democratic Republic of Congo, it was sold to local African diamond dealers. They went on to sell it to a group of Lebanese buyers from Kinshasa. 

The Incomparable Diamond travels to Antwerp, Belgium

The Kinshasa buyers brought the stone to Antwerp, Belgium. Antwerp had already established itself as the City of Diamonds long before the 1980s. There, the Incomparable Diamond was bought by a senior from the De Beers Company. The precious gem was then submitted for examination. This was carried out by the Director of De Beers and President of the Central Selling Organization – Sir Phillip Oppenheimer. The Central Selling Organization is responsible for a large part of the world’s diamond trade. Oppenheimer was astonished by the diamond’s color and its enormous size. However, he decided against keeping it as part of the De Beers collection. 

The Incomparable Diamond arrives in the US

Sir Philip Oppenheimer sold the stone to Donald Zale. He was the chairman of the board of a Dallas-based jewelry store chain – the Zale Corporation. Donald Zale bought the Incomparable Diamond alongside two other prominent diamond dealers. They were both based in New York. One of them was Louis Glick and the other one Marvin Samuels. Samuels was part of the Premier Gem Corporation. Up until this point, the gemstone had remained hidden from the public.

It was finally unveiled in November 1984 for the Zale Corporation’s 75th anniversary. After this, the Incomparable Diamond was put on display in Washington DC as part of the Smithsonian Institute’s gem collection at the Natural History Museum. It is important to note that the diamond was only lent to the Smithsonian. It remains part of the private collection of the three gentlemen.

The Technical Characteristics of the Incomparable Diamond

The Incomparable Diamond is a fancy deep brownish yellow color diamond. During the cutting of the diamond, it was discovered that the Incomparable appears to vary in color, which was unusual. In the early 1980s when the cutting was still underway, the Smithsonian Institute was invited to assess the stone. The curator of Mineralogy at the time, John Sampson White was tasked with this. The color variation was big, some parts were nearly colorless, some were pale yellow, and some had a little brown overtone but were rich yellow.

White used his expertise to determine that the gem was not uniformly colored during its creation. The crystal, he suggested, had been composed of strictly defined areas of different colors. Changes in the environment whilst the diamond was forming were represented by the different colored areas. The gem probably started as colorless, then a layer of pale yellow, and finally the rich yellow with a slight brown overtone. This is what caused the variation in the 15 diamonds that were eventually cut from the rough stone.

The Incomparable Diamond is the largest faceted yellow diamond in the world

The Incomparable Diamond weighs 407.48-carats and is the largest gem out of the 15 that were cut from the rough stone. The other 14 vary in size with the largest being 15.66 carats and the others ranging from 1.33-6.01 carats. The Incomparable possesses the second-highest clarity grade awarded – IF (internally flawless). The cut of the diamond is unique. Scholars describe it as a shield-shaped step cut. Marvin Samuels who was part-owner of the gemstone and headed the diamond cutting team describes it as a “triolette shape”. This makes the Incomparable the largest faceted yellow diamond in the world and 3rd largest faceted diamond. The first two are the Cullinan I at 530.20-carats and the Golden Jubilee at 545.67-carats.

The Significance of the Incomparable Diamond

The Incomparable Diamond is truly remarkable. It is not hard to see how special it is, considering its size, the craftsmanship that went into cutting it, and its unique color.

The incomparable diamond’s price is too high for bidders

However, that has put a price on it that seems unreachable for most people. The diamond was auctioned at a reserved price of $20,000,000 in 1988. Nobody bid over $12,000,000 and the stone remained unsold. At the time, that was the highest bid ever offered for a single diamond. 

The Incomparable Diamond appears on eBay

There is also a rumor that the Incomparable Diamond was once put up for sale on eBay in the early 2000s. The starting price was $15,000,000 but the precious gemstone remained unsold once again. Interestingly, the eBay auction did not mention the name of the diamond anywhere, which is why some people believe it may not have been it.

The Incomparable Diamond today

The Incomparable Diamond failed to sell at both auctions and its whereabouts are unknown. There are no records of any sales, so the diamond is, most likely, still owned by the group of three gentlemen who purchased it in the 1980s.

We hope you enjoyed the read!

If you’d like to read about other famous diamonds like the OrlovEureka, or Premier Rose diamonds, you can visit Ajediam’s Famous Diamonds glossary. Or, if you’re feeling inspired, you can browse Ajediam’s premium diamond collections shop.