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Lesedi la Rona

Lesedi la Rona

The “Lesedi la Rona” At 1109-carats, the largest gem-quality rough diamond to be discovered in over a century and the largest rough diamond in existence today. Estimated in excess of $70 millionCredit: Donald Bowers/Getty Images for Sotheby's

A rough diamond weighing a remarkable 1,109 carats will be auctioned in London by Sotheby’s on 29th June 2016 with an estimate in excess of US$70 million.


The stone was unearthed by Lucara Diamond Corp. at their Karowe mine in Botswana in Novemer 2015, with a press release indicating that the rough weight was 1,111 carats.  While it’s unclear what happened to the missing 2 carats of this stone since then, the Lesedi la Rona is still the largest diamond to be unearthed since the Cullinan Diamond in 1905.  Its discovery knocked the 603 carat Lesotho Promise off the second to top spot – a position it had occupied for a mere ten years. 

The Cullinan weighed a whopping 3,016.75 carats and produced nine major diamonds which are set into the Crown Jewels of the UK, including the Great Star of Africa (Cullinan I), which holds the title for the largest ’D’ colour polished diamond in the world at 530.20 carats*.  If the Lesedi la Rona were to be fashioned into a single stone rather than being divided into several separate parts, it could very well take the top spot in the diamond league tables for a cut stone.  However, when the Losotho Promise was fashioned, it delivered 26 ‘D’ colour stones with the largest one being a 75 carat pear-shape.   

Until the diamond is fashioned, there is no way to tell exactly what colour and clarity the resulting stones will be, however independent experts have commented that the stone is likely to be a Type IIa (chemically pure carbon), and that any cut stones have a high probability of being ‘D’ colour – the highest classification of white colour in a diamond.

It is quite possible however, that the new owner of the stone will decide not to fashion the gem.  In its rough state it is already a museum-worthy article.  Of course there will be enormous speculation over the fate of this stone, not least of which will be the price it may attain at auction.


The Lesotho Promise was sold in its rough state at auction in Antwerp (a city famed for its historical connections with the diamond trade) in October 2006.  The selling price was US$12.4 million.  This equates to a cost per carat of US$20,500.  Applying this same price structure to the Lesedi la Rona gives us a figure of US$22.8 million.  So where has this figure of US$70 million come from?

First of all, we must consider the locality of the sale.  While Antwerp is big in the diamond world, being described as “the international diamond capital of the world” by Freddy J Hanard of the HRD in Rapaport 2006, it is still a bit of a closed market to the outer world. Sotheby’s, in comparison, is one of the world's leading auction houses, with a client list which includes some of the wealthiest people on the planet.  

Secondly, we must give thought to the convenience and speed of the publicity and marketing at play today.  In 2006 the internet was not widely accessible and social media was in its infancy.  Facebook only launched its news feed in September of that year and Twitter launched in July.  A lot more people will know about the Lesedi la Rona than were aware of the Lesotho Promise.   


Then there is inflation and the rise in the market to consider.  A more accurate comparison is to The Constellation – an 813 carat rough diamond also mined by Lucara Diamond Corporation in November 2016 – which was sold for US$63 million on Monday 9th May.  If we apply this dollar per carat price to the Lesedi la Rona, it could fetch US$86 million (source- Bloomberg).  But that still doesn’t take into account the fact that the Lesedi la Rona is over that magic 1,000 carat figure.  We talked about the jump in price for diamonds when they reach whole numbers in Shirley Temple – the Bluebird that Failed to Fly.  This same principle will almost certainly apply in this case.

So why are we seeing so many more enormous diamonds on the market at the moment?  What are these diamond companies doing differently?  Well, as yet, we are unsure.  To the best of our knowledge, there have been no significant changes to mining methods in the last few years.  In order to get diamonds out of a diamond-bearing volcanic pipe, explosives are used to release the diamond-bearing ore (see our article Diamonds - An Introduction for more detail on this).   The ore is then crushed to release the diamonds before extraction.  These methods obviously carry with them the risk of breaking up larger gemstones into smaller fragments.  

Lucara Diamond Corporation has either found a more gentle way to extract the diamonds from their rocky home, or they are blessed with exceptional good luck. There is a whisper in the gemmological community that they are taking another step along the process to avoid crushing the ore after the explosive stage, but we have yet to hear confirmation on this.  Either way, their stock prices had risen by a massive 32% after the sale of The Constellation on Monday (Source - Forbes) and they seem to be in for a bumper year. 

The Lesedi la Rona will be on view at Sotheby’s London from 18 until 28 June ahead of its auction in the evening of 29th June.

*The largest gem quality diamond in the world is the Golden Jubilee at a hefty 545.65 carats, but this does not have that coveted 'D' colour, showing a brown hue instead.  The rough for this stone came from the Premier Mine, and was manufactured (cut) by Tolkowski (inventor of the modern round brilliant cut) in the late 1980’s.  

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