David explores the cult of the 100 carat diamond

The announcement last month of the discovery of what is claimed to be the third largest rough diamond ever to have been unearthed, raised a number of questions for me about the future of such massive stones – and reminded me of some of the polished gems to which they give birth.

Weighing in at no less than 1,098 carats this particular diamond was recovered by Debswana, a joint venture between the government and De Beers in Botswana. Of course, this is not the first gigantic diamond to be found in Botswana in recent years – many will remember for example the now famous Lesedi La Rona. The Lesedi was in fact very slightly larger than the stone announced last month. Weighing 1,109 carats meant that when it came up for sale at Sotheby’s in June 2016 it was possible to bill it as the largest rough diamond to surface in over 100 years – since in fact the discovery of the legendary Cullinan diamond in South Africa in 1905.

The Cullinan weighed a whopping 3,106 carats and was to be the origin of a number of the most famous diamonds in the Crown Jewels including the Great Star of Africa, which at 530.4 carats is still the largest top colour diamond in the world

I was holding the hammer at the auction of the Lesedi La Rona in 2016 and was naturally disappointed when the bids failed to meet the reserve. The diamond however was subsequently sold in 2017 for $53 million to the ‘King of Diamonds’ Laurence Graff. The main stone cut from it is the world’s largest D colour emerald-cut diamond weighing 302.37 carats, as well as an additional 66 satellite stones ranging in weight up to 26 carats.

Very large diamonds have always held a fascination for me. In the autumn of 1990 I decided to take the risk of offering a 100 carat perfect white diamond at auction at Sotheby’s in Geneva. The stone had been cut very recently and had never been worn – or scarcely even seen – before its appearance in the auction catalogue. Having discussed the matter with the owner we felt certain that auction would be the right route for a stone of such importance and rarity as it would be the first 100 carat top colour diamond ever to be presented at auction. It would also be the most valuable diamond or precious stone ever to have been sold at a public sale – the pre-sale estimate alone was in excess of $12 million.

The sale announcement caused quite a stir: we had also decided to announce that the buyer would be given the chance to name the stone – the first time such an idea had been proposed, and it proved to be very infectious – conferring a special notoriety on the sale and adding a highly attractive bonus for buyers

There were a number of factors that had influenced my decision to go ahead with the auction: the first point I took into consideration was that it seemed obvious that a diamond of this size and importance would catch the eyes of the world’s press, and would also, with luck, catch the attention of prospective buyers and investors in search of exceptionally rare gemstones. Secondly, prices for large diamonds had been escalating over the preceding five years, especially for rare stones of top quality, and the market felt rather positive for taking risks.

But then, quite unexpectedly, disaster seemed to strike in the shape of Saddam Hussein deciding to invade Kuwait! The markets and commodity prices worldwide went into turmoil. The Middle East was sent into panic. However, out of the ashes came a bright hope. I remember showing the diamond to a gentleman from that region who had expressed interest in such an exceptional stone. Having established, somewhat naively, that he was not considering the purchase as a gift for his wife I asked him the real reason. He replied quite simply: ‘tell me any other way I can put $12m in my pocket!’. Of course this aspect of portability, combined with intense concentration of value, is something that has been associated with gemstones for centuries – but it is only relevant in times of great troubles when the idea of fleeing with all you own looms on the horizon.

The sale was a great success and the stone sold for a world record price to a huge sense of relief within the diamond trade and a sense of astonishment among the public at large. The press coverage sparked a sudden desire among the super-rich for 100 carat D colour, internally flawless gems – such that by the end of 1995 I had sold two more, each of them selling for more than the last. Each of these sublimely rare stones was different and to me had a completely individual character. All three had an undeniable beauty and presence.

All of this had the important, but perhaps unexpected, outcome that, from that point on every cutter would examine every large rough appearing at tender with an eye on whether cutting a 100 carat stone would be achievable. This became the Holy Grail, and of course pushed up the price of these exceptionally large rough diamonds even further. Before this new craze for 100 carat gems, a cutter would examine a large rough diamond with a view to determining, first and foremost, the maximum ‘yield ‘, in other words the greatest number and combination of polished diamonds that could be cut from it, having taken into account the existence of flaws, etc. This could be a nerve-racking business, as in order to cut a 100 carat diamond, the cutter would have to decide to sacrifice a number of smaller diamonds (which may well have been easier to sell), and, instead, to put all his eggs in one basket. After 1990, and the sale of the first 100 carat stone for a very large premium, the decision became easier!

Although they remain extremely scarce, the number of extremely large rough diamonds appearing at tenders has grown in the last ten years or so, due, in large part, to two significant changes to how these stones are mined, which I will briefly outline: the first is that the mines have introduced a new process whereby the diamond-bearing host rock is x-rayed (as diamonds are opaque to x-rays) before the initial crushing so that large rough diamonds can be removed before potential damage. The second factor is that the calibration of the selection process of the host kimberlite has been raised so that larger rough gems are not damaged in the sorting operation before the crushing process. Both these changes have had a positive effect on the size and quantity of the large rough now being recovered.

I look forward with great anticipation to see what new treasures will be uncovered in the coming years and what beautiful polished diamonds the skills of the cutters will be able to reveal from them

Further reading: At Sotheby’s, ‘The 100-carat’ Man, David Bennett interviewed by Elizabeth Paton for the New York Times, Sept. 11, 2016 | Read the article here