Record-Breaking Diamonds

Introduction

This report sets out to tell the story of exceptional diamonds.

While the narrative begins with historic rough discoveries, it also explores other milestones – polished diamonds that achieved landmark prices, headline-grabbing auction pieces and gems now enshrined in museum collections.

With ongoing advances in mining and recovery techniques, it seems likely that even the long-standing 3,106-carat milestone of the Cullinan will eventually be surpassed, adding a new chapter to an ever-evolving story. Remarkable diamonds have captivated people for centuries. We hope this report serves as a vivid and compelling reference for all those drawn to their enduring brilliance.

Image: Lesedi La Rona rough diamond on display. Credit:  Getty Images / Spencer Platt

Giant Gemstones of History

1. The Cullinan Diamond

On January 25, 1905, while inspecting an upper section of the Premier Mine (today the Cullinan Mine) near Pretoria in South Africa’s Transvaal Colony, mine manager Frederick Wells caught sight of a flash of light. It was the sun’s reflection glinting off the rock face about 18ft below the surface. Using his pocketknife, he freed a massive, glass-clear crystal and carried it to the mine office, reportedly exclaiming, “My God, look what I have found!” The 3,106-carat rough was soon confirmed as the largest gem-quality diamond ever discovered⁵.

News of the find spread quickly, and the press dubbed it the Cullinan Diamond, after mine owner Sir Thomas Cullinan. Amid speculation over who could afford such a gem – and at what price – the owners sent it to London for safekeeping while they searched for a buyer. Still unable to find a buyer or agree on its value, the Transvaal government purchased it in 1907 for £150,000 – an estimated $23 million in today’s terms – and presented it as a gift to King Edward VII⁶.

“Look what I have found”

Images: Top: Cullinan Diamond, rough. Joseph Asscher makes the initial cut. The shapes and cuts of the nine major stones cut from the Cullinan diamond. Credit:  Royal Asscher

At De Beers’ recommendation, the King entrusted Amsterdam’s Asscher Diamond Company (now Royal Asscher) with cutting the stone.  It yielded 105 polished stones comprising nine major polished diamonds which became part of the royal collection, with two later set into the Crown Jewels⁷, and a further 96 minor brilliants. 

Today, Cullinan I and II remain among the world’s most recognisable diamonds – admired by 3 million visitors in the Tower of London as part of the British Crown Jewels and ceremonially worn by the monarch at the annual opening of parliament and at coronations. They stand as enduring symbols of the extraordinary journey diamonds undergo: forged billions of years ago deep within the Earth, carried to the surface by volcanic forces, noticed by chance in a glint of sunlight, and transformed through human craftsmanship into the very embodiment of royal grandeur for more than a century.

Image: Coronation portrait of Queen Elizabeth II holding the Cullinan sceptre and the Cullinan crown. Photographer: Cecil Beaton. Collection: Royal Collection

Geological Factors

The power of origin

Diamonds are survivors. Those that reach the Earth’s surface have endured a journey spanning millions – even billions – of years. Formed deep within the mantle, mostly at depths of 150 to 200km below the surface they are carried upward by rare and violent volcanic eruptions – the most rapid known to man. As the magma cools, it crystallises into volcanic rocks known as kimberlite or lamproite, which serve as the diamond’s delivery system to the surface. It’s a testament to the resilience of diamonds that they can survive such an intense ascent as the magma has the capacity to dissolve the diamond – and an even greater wonder when stones of exceptional size make it all the way intact.¹⁷

What large diamonds teach us about the Earth

The world’s biggest diamonds offer unique insight into the hidden secrets of the earth’s deepest interior. Research first published in 2016 by GIA in the journal Science and then a second publication came in 2017 in the journal Gems & Gemology, showed that record-size stones like the Cullinan, Lesotho Promise, and other large Type IIa diamonds belong to a distinct group, which form far deeper than ordinary gems – between 360 and 750 kilometres beneath the surface, in the Earth’s mantle transition zone.¹⁸

These so-called ‘CLIPPIR’ diamonds are named for their shared traits: ‘Cullinan-like’, ‘large’, ‘inclusion-poor’, ‘pure’, ‘irregular’, and ‘resorbed’. The GIA researchers found that they contain microscopic traces of iron and nickel, surrounded by methane and hydrogen. That means these giant gems were born in liquid metal rather than silicate magma, which helps explain their exceptional size, purity, and lack of nitrogen.

That discovery changes what we know (because this is going back almost 10 years to 2017) about the Earth’s interior, as we cannot directly sample these great depths in our planet. Each of these diamonds carries clues about how carbon, oxygen, and other elements cycle through the planet’s interior, offering a rare glimpse into the deep processes that have shaped the Earth for billions of years.

Oppenheimer Diamond Collection # 6513. Diamond in kimberlite matrix, 52.45 ct. Sir Oppenheimer Student Collection. Credit: GIA, photographer Robert Weldon.

Cutting the Titans

Carving a royal legacy 

The Cullinan wasn’t the first super-sized diamond the Asscher Diamond Company cut and polished. The Amsterdam-based firm, run by five Asscher brothers, had already built its reputation on the Excelsior. At 995.20 carats, it was the largest rough gem-quality diamond ever discovered before the Cullinan.^{40, 41, 42}

Even so, the 3,106-carat Cullinan demanded a far deeper level of analysis. Its sheer scale was one factor, but the ownership of the stone and the intense public attention surrounding it raised the stakes even further.

On the recommendation of De Beers, King Edward VII invited the Asschers to assess the diamond. Two of the brothers – company head Abraham and master cleaver Joseph – travelled to Buckingham Palace to view the stone and make a proposal, which the king accepted.

The first challenge was simply getting the diamond from London to the Asscher workshop in Amsterdam. Newspapers were told it would travel in a sealed box aboard a British Navy destroyer, a bit of deliberate misdirection. In truth, Abraham slipped the Cullinan into one pocket of his jacket, kept a gun in the other, and quietly boarded a regular passenger ship. That’s according to his grandson Edward Asscher, veteran diamantaire and former CEO of Royal Asscher, the modern successor to the family business, which is today managed by his children Lita and Mike.

Image: Joseph Asscher cutting table. Credit:  Royal Asscher

Cleaving the Cullinan

With the Cullinan safely in Amsterdam, the brothers spent months studying it. Their assessment made it clear they would need to cleave the Cullinan, splitting it into two parts. In practice, they had to execute two cleavages. Near its centre, the rough stone held several black inclusions that had to be removed, and the planned layout of additional smaller stones required a structure that would allow for consistent, workable polishing.

Meanwhile, Joseph Asscher had custom tools made that he believed were essential for cleaving a diamond of the Cullinan’s size. Once they were ready, he set to work, spending the next month carving a precise incision roughly one centimetre deep. By early February 1908, he was finally prepared to attempt the cut of the largest gem-quality rough diamond ever found.

The cleaving became a public spectacle. The room filled with family members, journalists and a representative of the king, all waiting to witness the moment. The drama came quickly. When Joseph finally delivered the blow, the diamond held firm while the knife blade snapped instead.

He cleared the room, then deepened the incision in the stone, and the adjustments worked. When he attempted the split again, the diamond cleaved cleanly, this time with only a small group present, including the King’s representative.

A persistent legend claims Joseph fainted after the first attempt, though the family has always dismissed it. In fact, after successfully cleaving the stone exactly as calculated, he invited everyone back in for a champagne celebration. Maybe he fainted after the party, the family likes to joke.

Royal destiny

The Asscher team spent the next two years polishing the Cullinan, largely because of the sheer number of stones it yielded. They ultimately presented the crown with nine major polished diamonds destined for the Royal Collection, along with another 96 smaller stones. Little is known about those smaller stones today.

The nine larger diamonds are the ones that cemented the Cullinan’s legacy, and they remain embedded in British royal tradition and folklore.

The largest of the gems, Cullinan I, known as the Great Star of Africa, remains the biggest colourless polished diamond on record at 530.20 carats. It is graded D colour and potentially flawless. Cut into a pear shape with 74 facets, it sits at the heart of the Sovereign’s Sceptre with Cross, the signature piece of the British Crown Jewels. Its sister stone, Cullinan II, the Second Star of Africa, is a 317.40-carat cushion cut, also D colour and potentially flawless, positioned prominently at the front of the Imperial State Crown^{43, 44}.

Cullinan Diamonds original box with tools. Credit: Royal Asscher

The Cullinan III and IV Brooch (C) and Cullinan VII Delhi Durbar Necklace. Credit: Getty Images / Samir Hussein

A brooch that bridged monarchs or A brooch that bridges monarchs^{45, 46}

Among the many standout jewels in her collection, Queen Elizabeth II reserved a particular brooch for her most significant appearances. Set with the Cullinan III, a 94.4-carat pear shape, and the Cullinan IV, a 63.6-carat square cut, the piece accompanied her during her Diamond Jubilee in 2012.

After her passing, the diamonds reappeared in Queen Camilla’s coronation crown, as they had in the same crown worn by Queen Mary at her coronation in 1911. Outside of such moments, the crown uses replicas of the Cullinan III, IV, and V so the originals can continue to circulate as brooches.

For the Asscher family, the most meaningful moment came in 1958, when Queen Elizabeth wore the brooch during her state visit to the Netherlands. She visited the Asscher offices, where the Cullinan had been cut and polished, and met Louis Asscher, the last surviving of the five brothers.

During that meeting she told him, “Here, Mr. Asscher, you can take them in your hands. You held them in your hands before.” Despite his failing eyesight, Louis recognised the stones instantly and was deeply moved by the gesture.

The Hope Diamond

The Hope Diamond⁵¹ ranks among the most mysterious and storied gems in history. Believed to have originated in India’s Kollur mine, it passed through French and British royal hands, earning a reputation for bringing misfortune to its owners. Originally part of the French Blue⁵²– a 67-carat diamond owned by King Louis XIV – the diamond was stolen during the French Revolution in 1792 and later recut into its present form.

It resurfaced in London in the early 19th century, where it was acquired by banker and gem collector Henry Philip Hope, after whom it is named. Over the next century, it passed through several notable owners, including American socialite Evalyn Walsh McLean, before being purchased by jeweller Harry Winston, who donated it to the Smithsonian in 1958.

Graded by the GIA⁵³ as a 45.52-carat fancy dark greyish blue diamond of VS1 clarity with very good polish and symmetry, the Hope Diamond has captivated more than 100 million visitors since its arrival at the Smithsonian, making it one of the most viewed and celebrated diamonds in history.

The Hope Diamond. Credit: Chip Clark, Smithsonian’s National Museum of Natural History (digitally modified by SquareMoose)

The Regent Diamond

The Regent Diamond CREDIT: Creative Commons CC0 1.0 Universal Public Domain Dedication

The Regent Diamond, a 140-carat diamond of almost unreal perfection, is considered one of the most symmetrical old-cut diamonds in history – a remarkable feat for a stone cut and polished in the early 1700s⁵⁴. Its exceptional clarity, described as perfectly transparent, and its ‘first water’ white brilliance has earned it an almost mythical reputation for centuries.

Discovered in 1698 in the legendary Golconda mines in India, the rough stone weighed nearly 410 carats before being transformed into a sumptuous 140.64-carat cushion-cut diamond, with an estimated colour of D or E and perfect or near-perfect clarity – one of the most accomplished masterpieces of old-cut diamond cutting.

Acquired by Philippe d’Orléans, then Regent of France, the diamond became one of the most cherished jewels of the French sovereigns. It successively adorned the crown of Louis XV, then that of Louis XVI, before shining on the sword of Napoleon Bonaparte⁵⁵, embodying through each reign the continuity of a sovereign light.

In 1887, when the French Crown Jewels were sold, the Regent was miraculously preserved and incorporated into the national collections. Today, it remains in the Louvre Museum.