For well over a century, the Oppenheimer name has almost exclusively been associated with that most luxurious of coveted items – diamonds.

It is, therefore, not surprising that there is more than one famous diamond that has been named in honour of the family. While considerable attention has recently been lavished on the 14.62 ct Oppenheimer Blue, which was sold at a Christie’s auction in May for a cool $57.6-million, there is another magnificent diamond, bearing the same name, equally deserving of the gemological limelight.

There are many features of the 253.7 ct Oppenheimer diamond that make it one of the rarest and most unusual stones yet discovered. Most important is the fact that it is the third-largest uncut diamond in the world – at least of those that are in the public domain. (The first is the 1 111 ct Lesedi La Rona, discovered in Botswana last year, while the second is the 616 ct yellow Kimberley Octahedral, which was discovered in the Dutoitspan mine in 1964 and remains in the possession of De Beers Consolidated Mines (DBCM) on account of the exceptional rarity of the specimen.)
Secondly, the natural form of the stone is an almost exact octahedral (eight-sided), making it an almost perfect representation of one of the common theoretical forms in which natural diamonds crystalise.

The intense yellow colour of the Oppenheimer diamond is another feature that adds to its rarity. While naturally coloured diamonds are quite unusual, large yellow diamonds are particularly rare. There are only four other yellow diamonds weighing over 100 ct that are worthy of mention. Although the Kimberley Octahedral is certainly the largest of the yellow diamonds, the most famous is, undoubtedly, the magnificent 128.54 ct cushion-shaped Tiffany, discovered in the Kimberley mine in 1879 and still in the possession of the world-famous American jeweller. The third is the 100.09 ct cushion-shaped Graff Vivid Yellow, which made headlines in May 2014, when it fetched $16.3-million at a Sotheby’s auction. And then there is the 234.64 ct De Beers, which was discovered in Kimberley around the time of the establishment of DBCM in 1888.

The history of the Oppenheimer is as equally fascinating as its natural form. The stone was discovered in 1964 in the Dutoitspan mine, which was, interestingly enough, the same mine and year in which the Kimberley Octahedral was found. The Dutoitspan mine, which is still in operation 146 years after its discovery, has yielded a fair percentage of South Africa’s gem-quality coloured diamonds, particularly of the yellow-brownish hue.
Soon after its discovery, the diamond was bought by Harry Winston, arguably the most famous jeweller and diamond collector of the twentieth century. It is said of Winston that about a third of all the world’s famous diamonds passed through his hands at some point.

Winston bought the diamond directly from De Beers, a company with which he had first established relations in 1935, when he famously bought the 726 ct Jonker Diamond for a hefty $750 000 ($29.2-million in today’s terms). Interestingly, that is regarded as his first important purchase and the one that established Winston as a major buyer, connoisseur and collector of large gem-quality diamonds.

Following the purchase, Winston christened the diamond the Oppenheimer in honour of the King of Diamonds himself, Sir Ernest Oppenheimer.
Although he could have quite easily cut the stone into a gem of significant size and sold it on for a substantial profit, Winston opted to donate the Oppenheimer to the Smithsonian Institute’s National Museum of Natural History, in Washington DC. While such a donation may seem almost inconceivably altruistic, there was certainly a motive behind the grand gesture.

Winston was an inherently patriotic man who believed in the greatness of the American way of life. Thus, it is not surprising that one of his greatest sore spots was the fact that his beloved country lacked a national jewel collection that could rival the great collections of Europe.

This view was shared by George Switzer, who, in the mid-1950s, was the acting mineralogy curator for the Smithsonian Institute. More to the point, Switzer believed that the institute, as America’s leading museum and archive repository, required a first-class gem collection that could be used for research and educational purposes.

While the Smithsonian Institute certainly had a decent mineralogical collection, it severely lacked first-class diamonds and gems of any significance and it is for that reason that Switzer approached Winston to donate some of his prized stones to their collection.

Thus, between 1958 and 1964, Winston, in the interest of building a prized national collection, donated a number of diamonds to the national collection, including (most famously) the 45.52 ct Hope, the 127.01 ct Portuguese and the Oppenheimer.

The Oppenheimer has remained in the Smithsonian diamond collection since 1964 and is usually kept in its famous and highly secure Gem Vault, along with the other famous stones. It is highly likely that the Oppenheimer will remain in their possession for the foreseeable future.