The Jonker Diamond

The First World-Famous Diamond That Toured The US

Discovered in 1905 by Johannes Jacobus Jonker, the Jonker diamond’s colorless shine and near-perfect clarity turned it into the most coveted thing on earth overnight. At the time of its discovery, the stone was the fourth largest rough diamond of gem quality ever found. The Jonker’s clean, colorless shine and near-perfect clarity turned it into a worldwide sensation. Cut by Kaplan Lazar, one of gemology’s most iconic cutters, the Jonker ended up mesmerizing all who laid eyes on its final form. The stone’s legacy lives even to this day because it is the first of its caliber to be cut in the United States and was last resold in 2017. 

If you’d like to learn more about the Jonker diamond’s origins, technical details, and significance, in this article you will find:

Jonker Diamond. Bettman / Corbis
Jonker Diamond. Bettman / Corbis
Discovered in
Country of Origin
South Africa
Mine of Origin
Elandsfontein mine
Carat Weight
Originally weighed 726 carats, cut into 13 individual diamonds ranging from 142.9 to 5.7 carats. Jonker I recut to 125.35 carats.
Cut Shape
Emerald cut (Jonker I)
Jonker I: VVS2 clarity grade (very very slightly included)
Jonker I: D-color grade (completely colorless or very close to being so)
Previous Owners
  • Johannes Jacobus Jonker and family
  • Joseph Bastianen (agent of Diamond Corporation Ltd)
  • Sir Ernest Oppenheimer
  • Harry Winston
  • King Farouk of Egypt
  • Queen Ratna of Nepal
  • Anonymous buyer in Hong Kong (1977)
  • Various buyers for the smaller diamonds (Jonker II, IV, V, VII, XI, XII)
Current Owner
The Jonker I was last resold in 2017 to an undisclosed buyer in Hong Kong.
Estimated Value
The most recent auction in 2017 saw Jonker V sold for 5.3 million USD, more than 50% larger than presale estimations, due to a bidding war. The value of the entire Jonker Diamond and its individual pieces can vary significantly based on market conditions and collector interest.

The Origins of the Jonker diamond

The life of Johannes Jonker: a poor diamond digger

Johannes Jacobus Jonker was one of many diamond diggers who were looking for fortune deep within the earth. He was ultimately responsible for the stone’s unearthing, although for  18 years he hunted for buried treasure without any luck. Regardless of his lack of success in his search for rough diamonds, he did succeed in other areas. Johannes was a father of seven children. In spite of his vast family, the man had nothing to show for his decades-long efforts. Perhaps at some point, a potential discovery seemed distant for Jonker, but on a cold and rainy day, the 17th of January of 1934, he sent his son, Gert, to the Elandsfontein mine. It was in this instant that the frustrated digger’s luck was about to change. 

One of Jonker’s helpers, South African national Johannes Makani, was washing a bucket full of gravel when he found a strange muddy object. As he washed and brushed, his eyes began to widen with disbelief. A large crystal clear diamond was in his hands. Overjoyed, he brought it to Gert Jonker, who then rushed with the diamond in full gallop to his father. Once the old Johannes realized what they had found, he reportedly fell on his knees and praised God.

The life of Johannes Jonker: lady luck’s blessing

After a  lifetime of poverty, the Jonkers couldn’t believe their fortune.  Deprived of their peace of mind, they were obligated to guard the stone with loaded revolvers. The diamond put the whole family in a state of constant anxiety. Mrs. Johannes even hid the diamond in a stocking, which she carried wrapped around her neck. Soon enough they were able to sell the diamond to Joseph Bastianen, an agent of the Diamond Corporation Ltd for an estimated sum of around £75000. Yet, misfortune continued to plague the life of the Jonkers. The South African authorities were tipped off about the negotiations, at which point they demanded a cut of the sale in the form of a third of the stone’s value in taxes. The tax seemed incredibly unjust, as the government had done nothing to help him during their 18 years of hardships. 

Yet, being a god-fearing man, Johannes decided to pay the tax. He then bought a farm, some animals, and a limousine with the rest of the money. This sudden influx of money thrust him into a high-spending lifestyle for which he was never prepared. This was disastrous for his finances and in a matter of a few years, he was back to the impoverished prospector’s shack where he had started from. Fame and fortune had passed him by for good. 

The international journey of the Jonker diamond 

Sir Ernest Oppenheimer, the owner of Diamond Corporation Ltd, is considered to be Jonker’s original owner. Only a year later after its discovery, in 1935, he sold the Jonker for an estimated 150,000 pounds to the American diamond collector Harry Winston. The sale marked a high point for the De Beers Central Selling Organization, as it was the first stone of its size to be sold to the US. Before being shipped to the US, the Jonker stayed in London for some time, during the Royal Silver Jubilee celebrations in 1935. There were public efforts to buy the gem as a gift for King George V and Queen Mary, but they ultimately failed. 

A curious note, and a recurrence in other famous diamond stories, is that both for shipping the gemstone from South Africa to London, and from London to New York ordinary registered mail was used. After the long transatlantic journey, it reached the office of Harry Winston in New York. Word about the largest diamond in the US quickly spread. Winston received many invitations to exhibit it. He consented to display it at the Natural History Museum. However, an unsolved problem remained – never had a gemstone of such size and quality been cut in the US, meaning that Winston’s quest to find a worthy cutter had begun. His choice fell on Lazare Kaplan. 

The Cutting of the Jonker Diamond

Harry Winston’s choice of Lazare Kaplan was no accident. Lazare had been a descendant of three generations of jewelers. His family had an outstanding reputation for cleaving and cutting diamonds in Antwerp, Belgium. Antwerp, as well as the Amsterdam diamond markets, had been the world’s capital for diamond cutting and trading. However, the First World War caused many diamond workers to flee from Belgium and start anew. Such was the case with Mr. Kaplan.

The Jonker is cut by Lazar Kaplan

Kaplan was known for being an excellent cutter and cleaver. He always brought out the best brilliance of rough gems, even if at a slightly greater cost of carat weight. Furthermore, Mr. Winston initially tested his abilities by assigning him to work on the smaller Pohl diamond. The Pohl had been a constant companion of the Jonker, albeit of lesser size and quality it originated from the same mine and was sold together with the Jonker. Lazare Kaplan passed Winston’s test with flying colors!

Impressed by Kaplan’s skills, Winston tasked him with the biggest gem-cutting challenge that had ever been faced in the US at the time. After months of preparation, studying the stone, and building a cleaving strategy, Kaplan did a brilliant job. On 27 April 1936, the Jonker was cut into 13 pieces, the largest of which was a 142.9 carat, D-color, emerald cut, and the smallest, a 5.7-carat baguette. However, the expert jeweler later found slight flaws in the Jonker I and recut it to 125.35 carats. Regardless of the reprocessing, the gemstone remained an emerald cut with 58 facets. Diamond experts consider Kaplan’s final work on the Jonker I as a masterpiece. The gemstone’s fame rose higher than ever before, attracting even bigger crowds. A true testament to Lazar Kaplan’s craftsmanship!

The Modern Ownership history of the Jonker Jewel

After its cutting, the Jonker I went on tour passing through various exhibitions around the US. Harry Winston also hired celebrities and models to showcase the beauty of the diamond and to further spread its fame far and wide. The Jonker I attracted the attention of the elite and royalty all over the world. 

The Kaplan effect: everyone wants it

The stone was eventually sold to King Farouk of Egypt in 1949. However, the sovereign was deposed and exiled in 1952, which rendered the diamond’s whereabouts a mystery. Some years later the infamous gemstone reappeared under the ownership of Queen Ratna of Nepal. It was under her care until 1977; when the Jonker was sold to an anonymous buyer in Hong Kong for a reported value of 2,259,400 USD.

What happened to the smaller diamonds?

The smaller Jonker diamonds did not attract as much attention and their movement was not tracked due to their smaller size. However, the Jonker II, with a weight of 40.26 ct, was sold at a Sotheby’s auction for the sum of 1, 975, 000 USD, in May 1994 in Geneva. The Jonker IV went to New York and was set in a platinum ring to be ultimately sold at an auction of Sotheby Parke-Bernet Inc. to a private collector for 277,000 pounds. In 1987, the Jonker IV was sold again in New York for 1,705,000 USD. Furthermore, there are reports that the Jonkers V, VII, XI, and XII were purchased by the Maharaja of Indore. While the Jonker X is rumored to have been purchased by John D. Rockefeller Jr. 

The most recent auction on any of the Jonker pieces happened in 2017 in Hong Kong, where the Jonker V was sold for 5.3 million USD to an undisclosed buyer. This sum is more than 50% larger than the presale estimations, due to a reported bidding war between buyers. 

The technical characteristics of the Jonker Diamond

The original Jonker diamond weighed 726 carats or 145.2 grams. Lazar Kaplan cut it into 13 individual diamonds, weighing from 142.9 to 5.7 carats. It had an elongated shape with the greatest length and width being 63.5mm and 31.75mm. The Jonker I had to be recut to 125.35 ct to remove some flaws and improve its brilliance. The Jonker I is an emerald cut, with a D-color grade, and VVS2 grade, type IIa for clarity. D is the best color grade a diamond can get. It means the diamond is completely colorless or very close to being so. VVS stands for very very slightly included. A type IIa diamond has no measurable nitrogen impurities. Altogether, this makes the Jonker I diamond one of exquisite color and clarity quality. 

The significance of the Jonker Diamond

At the time of its discovery, the Jonker diamond was the fourth-largest rough diamond ever found. Its color and clarity matched its superior size and made the gemstone one of the best quality diamonds in the world. Such was the fame of the Jonker, that enthusiasts even speculated that the Jonker was a long-lost fragment of the king of large diamonds – the Cullinan. There were merits to this story as both were discovered just five kilometers apart, in Transvaal. On its own, the Jonker I holds the record for being the largest Emerald-cut D-color diamond. In its prime, the diamond attracted the interest of celebrities and royalty, alike. We should not forget that the 1930s were a period marked by harsh economic conditions, hyperinflation, and massive unemployment. Perhaps the American public viewed the Jonker as a sign that the economy was turning around for the better, or perhaps it merely offered a desperately needed distraction from an otherwise grim period.

We hope you enjoyed the read!

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