The 2,400-carat Botswana diamond that rivals the Crown Jewels

In August, the second-largest diamond ever found saw the light of day. But who will be trusted to turn the stone into gems?

Natural light streams in from a wall-to-wall window where Eric, a diamond cutter (whose surname must remain a secret), is preparing a 782-carat rough diamond the size of a baseball to be sliced by an industrial laser. His view overlooks Antwerp’s diamond square mile, an intersection of three streets that’s a stone’s throw from the train station. Flanked by a police station and monitored by thousands of CCTV cameras, this area is home to the world’s most prestigious diamond trade: hundreds of millions of dollars circulate within these three streets, as diamantaires go about their business, pockets stuffed with 30-, 40- and 50-carat stones of the highest quality.
Eric is overseeing the cutting of a stone that started as a 1,080-carat rough. He works for HB Antwerp, a state-of-the-art diamond facility that has cut and polished some of the world’s most important and biggest diamonds in recent years. The company says that analysis of the 1,080-carat rough may yield some 35 stones in total, some of marmalade-dropping size: three identical stones of 100 carats – that’s 20g, or the equivalent of four seedless grapes. They might adorn a pair of earrings with a matching necklace; there is also a pair of 30-carat stones and another of 20 carats, alongside an array of smaller ones.
The stone was unearthed last year by Lucara Diamond Corp, HB’s exclusive partner and a Canadian mining company that’s been on a winning streak in recent years at its Karowe mine in Botswana, recovering at least six diamonds of more than 1,000 carats each.
In August Lucara unveiled its latest banger: a 2,492-carat diamond that became the world’s second largest, after the 3,106-carat Cullinan diamond. The latter, discovered more than 100 years ago, was cut up and set into the British Crown Jewels. Like many of Lucara’s mega stones, this latest discovery will undoubtedly make its way to Antwerp at some point, to be tackled by the world’s most sophisticated diamond cutters – and polished to sparkling life aided by today’s most up-to-date technology.
Natural diamonds are formed deep within the earth, and in the case of the recent spate of super-large stones, as far down as some 500km below the surface. Deep-seated volcanic eruptions of magma at a blistering 1,000C or so eventually propel the diamonds towards the surface, where miners working for the likes of Lucara drill and blast the earth to recover the stones.
Just as intriguing as how the stones arrive in human hands is how they’re later shaped, cut and polished by master craftsmen into multi-million-dollar sparkling stones. William Lamb, chief executive of Lucara, sums it up: ‘It’s the miners’ job to bring the diamond into the light, and the polisher’s job to bring the light into the diamond.’
When the Cullinan diamond was unearthed in South Africa in 1905, the stone the size of a human heart captured the world’s imagination. The government of the British-controlled Transvaal region gave it to King Edward VII, who commissioned Joseph Asscher, a third-generation diamond craftsman based in Amsterdam, to cut the stone. Several years earlier, Asscher had successfully cleaved and polished the Excelsior diamond, a 971-carat rough that was at the time the world’s largest.
Asscher spent months living and breathing the Cullinan rough. ‘He studied the diamond for nine to 12 months – all the fault lines, all the irregularities. He became one with the stone,’ says Mike Asscher, a great-grandson of Joseph and sixth generation in the family business (today he and his sister run Royal Asscher, an Amsterdam-based diamond company with a patented diamond cut inspired by the Cullinan). Joseph had one chance to cleave the stone – or risk it shattering into worthless pieces – and he even created his own customised tools for the task. With the world watching, the pressure was intense. ‘It was make or break for his career, but also make or break for the family’s history,’ says Mike Asscher. ‘Joseph knew that this was a moment to create world fame for our company, which would then continue for generations. Or it was, “If I fail, then we are done.” The pressure was immense.’
Diamonds are famously the hardest (that is, most unscratchable) natural material on Earth, and it is no surprise that cleaving the largest one ever found took two attempts. Asscher took weeks to create an incision 1cm deep. On 10 February 1908, he then wedged his splitting knife into this groove, only for his specially made tools to break on impact when he struck. The force of the blow also caused Asscher himself to reel backwards. Did the diamond maestro faint from the fear and shock? Or was he merely giddy from the Champagne that, surely unwisely, he’d drunk before striking? Either way, he had a funny turn before, armed with a new set of bigger knives and heavier blades, he successfully cleaved the Cullinan four days later (in the presence of a public notary). Splitting and cutting the diamond reportedly took eight months, with three people working 14 hours per day.
The Cullinan was eventually made into nine large stones – two of which are a whopping 530.4 and 317.4 carats – and 96 smaller ones. ‘The Cullinan was one of the most difficult diamonds in the world,’ says Asscher. ‘It was heavily included, and Joseph crafted nine large diamonds which were all clean, with no inclusions inside. That’s something I still think is spectacular.’
Back in Belgium, the days of employing only ‘eyes, hand and heart’ – to use Mike Asscher’s words – to cut and polish a rough diamond have given way to ultra-advanced diamond mapping and polishing technologies. For stones of more than 10 carats, Antwerp is still the go-to destination, with a handful of families in Israel also specialising in large stones. Meanwhile the majority of diamonds from 0.3 up to 10 carats are cut in India, home to some 90 per cent of the world’s diamond processing. More than a million people are employed in the Indian diamond industry, mainly based in the western city of Surat.
Top jewellery houses seeking those gobstopper-sized, couture-level high jewellery gemstones, however, still flock to Antwerp – with the best being HB Antwerp and Diamcad, both of which have invested heavily in building their own proprietary software and technology. When HB was founded in 2020, for example, it acquired a government-backed diamond research and development centre, and has since perfected a pioneering, end-to-end processing service that uses blockchain and verification technologies to trace a diamond’s journey, from the Lucara mine to the final polished stone.
Diamcad, meanwhile, has its own technology and has cut some of Graff’s most important stones to date. There was the Lucara-mined $53 million Lesedi La Rona, a 1,109-carat rough that produced the 302.37-carat Graff Lesedi La Rona, the world’s largest square emerald-cut diamond, alongside 66 satellite stones. Another was the Lesotho Promise, at the time the 15th largest diamond ever discovered, from which came 26 D-flawless diamonds of 223.35 carats in total. A pear-shaped diamond weighing more than 75 carats, a heart-shaped diamond of more than 43 carats, and a round brilliant exceeding 27 carats were among the highlights, and set into an extraordinary necklace of the same name. ‘Laurence Graff had a diamond fever for rough. If he saw a big stone, he wanted to buy it,’ recalls Bart De Hantsetters, co-owner of Diamcad and a fifth-generation family member to work in the trade.
Both HB and Diamcad point to a growing demand for large diamonds by the top jewellery houses, which echoes the size of roughs being recovered in recent years. And while the tools for transforming a diamond have come a long way, allowing bigger and bigger stones of matching size, shape and quality, in some ways the stakes are higher. Cutting a stone is still mired in peril, and mistakes are more costly than ever.
Not unlike Joseph Asscher becoming ‘one with the stone’ back in 1908, planning how to cut a rough diamond can easily take a year for the biggest. ‘Analysis of the stone is of critical importance,’ says Lamb. This generally begins with ultra-sophisticated CT scanners and microscopes – made for the industry – which create what De Hantsetters calls a ‘digital twin’ of the rough. This is essentially a map of both inside and out, from size and dimensions to all those tricky inclusions. Here one needs to be well versed in computer-aided design (CAD) and 3D product design, but the process also needs human brains.
After the digital twin is produced, small windows are polished on to the stone to verify inclusions. The more windows the better, of course, but this can also make the diamond smaller, shaving off tens of thousands of dollars in carat weight. Meanwhile, checking inclusions is as much art as science, where refraction can play tricks on the eye, so inclusions are not quite where they seem. Still, emphasises De Hantsetters, ‘You have to check a lot, with microscopes and special machinery, which can pinpoint the borders of the inclusions. We have to be completely sure before we make the final plan. Once you go to the laser, there is no way back.’
Next, you have to do the complicated 3D jigsaw of working out how many diamonds of the largest size and best cut can be made from the giant stone. For HB and Diamcad, this phase is notably tech heavy. Their software is fully loaded with algorithms that propose a host of shape options – oval, pear, round, cushion, marquise, baguette, emerald… on it goes. ‘The computational power you need to find all these possible combinations is huge,’ says De Hantsetters, whose company partnered with the Belgian research university KU Leuven to create the software. ‘The complexity is exponential.’
Then they slice the diamond. Long gone are the cleaving knives of Cullinan fame, which are now replaced by green lasers straight out of Star Wars. In HB’s case, these lasers are sized to a microscopic 50 microns (five hundredths of a millimetre), and paired with ultra-powerful water jets that not only guide the laser towards deep, narrow incisions, but also cool things down. Internal tension remains one of the biggest risks, as it means the heat generated by cutting a diamond can cause it to explode, leaving a cloud of diamond dust and a huge hole in the bank balance. Eric knows. On his first day as a cutter with a different company, a fault in the cutting laser caused a 3-carat stone to implode. Not even 0.3 carats was left to work with. ‘I still get goosebumps talking about it,’ he confesses.
The final stage is polishing. When you are working with the ne plus ultra of gemstones, every facet needs to be polished to perfection. Again, technology helps, but it’s still complicated, says De Hantsetters. ‘Polishing is about avoiding problems. It’s like playing chess. You have to be three, four, five steps ahead,’ he explains, adding that experience and dedication are key. ‘Like football, I can explain the rules and show you how to play. But to become a Messi or a Ronaldo, it takes many years and extreme dedication.’
As for the Lucara stone, the end result – the gobstopper rock destined to adorn some billionaire – is some way in the future. In the meantime its discovery has given a welcome boost to natural diamonds, facing threats from lab-grown varieties. ‘It truly is one of nature’s most wonderful gifts,’ says Mike Asscher of the new rough. And its journey is only just beginning.
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