TL;DR
On 26 January 1905, Frederick Wells pulled a 3,106-carat rough diamond — the largest gem-quality diamond ever found — from the wall of South Africa's Premier Mine with a pocket knife. Bought by the Transvaal government for £150,000 and presented to King Edward VII in 1907, it travelled to London by registered post while a guarded decoy sailed on another ship, and was cut into nine major stones.
Frederick Wells, surface manager of the Premier Mine near Pretoria, was inspecting the mine about eighteen feet below the surface on 26 January 1905 when a flash of light in the wall caught his eye. He dug it out with his pocket knife: a crystal about the size of a man's fist, weighing 3,106 carats — 621 grams — and it remains the largest gem-quality rough diamond ever found.
A Flash in the Mine Wall
The stone measured roughly 10.1 by 6.35 by 5.9 centimetres, exceptionally clear, with a blue-white hue. It was named for Sir Thomas Cullinan, chairman of the Premier Diamond Mining Company, who had opened the mine three years earlier. One side was a smooth cleavage face, suggesting the crystal had once been part of an even larger stone, broken apart by natural forces. No matching piece has ever been found. Displayed in Johannesburg, it drew an estimated 8,000 to 9,000 visitors — then it would not sell. Sent to London in April 1905, it stayed unsold for two years.
The Gift Nobody Could Sell
The way out was political. Louis Botha, prime minister of the Transvaal, suggested buying the diamond for King Edward VII as "a token of the loyalty and attachment of the people of the Transvaal to His Majesty's throne and person." The Transvaal had been defeated by Britain in the Second Boer War only a few years earlier, and the gift was meant as reconciliation. The Legislative Council voted in August 1907 — 42 in favour, 19 against — the government bought the stone on 17 October for £150,000, and it was presented to the king at Sandringham House on 9 November 1907, his sixty-sixth birthday. Edward accepted it "for myself and my successors."
The Parcel That Wasn't Guarded
Getting the world's largest diamond to London was, on paper, a security problem of the first order. The solution was to solve a different problem: what the thieves would be watching. A parcel was ceremoniously locked in the captain's safe aboard the RMS Kenilworth Castle, detectives were assigned to the ship, and the press followed its progress. It was a diversion — the stone on that ship was fake. The real Cullinan travelled separately, in a plain box, by registered post, and was inspected by the king at Buckingham Palace.
The trick was repeated for the second journey. Edward chose Joseph Asscher & Co. of Amsterdam to cleave and polish the stone. Abraham Asscher collected it from the Colonial Office on 23 January 1908 and travelled back to the Netherlands with the diamond in his coat pocket, while a Royal Navy ship carried an empty box across the North Sea to much fanfare. Even the captain, by one account, did not know his precious cargo was a decoy.
The Blow That Broke the Blade
Joseph Asscher studied the rough stone for weeks before touching it. A wrong blow while cleaving — splitting the crystal along a natural plane — would have meant fragments instead of great gems. A groove half an inch deep was cut to receive the blade; making it took four days. On 10 February 1908 Asscher struck. The steel blade broke. A second blade was fitted, and the stone split cleanly in two. The rest took eight months, with three men working fourteen-hour days. The rough yielded nine major stones totalling 1,055.89 carats, 96 smaller brilliants, and some unpolished fragments.
Nine Stones, Two Crowns
The nine stones were named by size, Cullinan I to IX. The Royal Collection Trust, which cares for the Crown Jewels, records that the two largest form part of the coronation regalia. Cullinan I, the Great Star of Africa, is a pear-shaped brilliant of 530.2 carats with 74 facets, set in the head of the Sovereign's Sceptre with Cross; the sceptre, made in 1661, had to be redesigned in 1910 to take it, and the mounting is hinged so the stone can be removed and worn as a pendant. Cullinan II, the Second Star of Africa, is a cushion-cut brilliant of 317.4 carats with 66 facets, set in the front band of the Imperial State Crown, below the Black Prince's Ruby — which, despite its name, is a large red spinel.
The other seven were Asscher's fee for the cutting, until the South African government bought them and presented them to Queen Mary in 1910. Cullinan III (94.4 carats) and IV (63.6 carats) were worn together as a brooch, known in the family as "Granny's Chips." The rest: V, an 18.8-carat heart; VI, an 11.5-carat marquise; VII, an 8.8-carat marquise; VIII, a 6.8-carat oblong stone; and IX, a 4.39-carat stone in a platinum ring. Examined at the Tower of London in the 1980s, Cullinans I and II were graded colourless type IIa — almost no nitrogen impurities, the purest category. The Imperial State Crown holding it was made in 1937 for George VI.
Why Has No Diamond Ever Beaten the Cullinan?
Part of the answer is arithmetic: no gem-quality rough found since 1905 has come close to 3,106 carats. Cullinan I was the largest cut diamond in the world of any colour for most of the twentieth century, until the 545.67-carat brown Golden Jubilee Diamond, also from the Premier Mine, eventually surpassed it. It remains the largest colourless cut diamond in the world.
Part of the answer is geological. Diamonds like the Cullinan belong to a family researchers call CLIPPIR diamonds — large, exceptionally pure, nitrogen-poor stones. Research led by GIA's Evan Smith, published in Science in 2016, found that such diamonds carry inclusions stable only at depths of 360 to 750 kilometres, far deeper than the 150 to 200 kilometres where most gem diamonds form. They appear to have grown from droplets of metallic liquid — iron and nickel, with traces of methane and hydrogen — and reached the surface through kimberlite eruptions, in the Cullinan's case an estimated 1.18 billion years ago: a sample of a part of the planet no human will ever visit, found eighteen feet below a South African field. It also has no price: never offered for sale since 1907, the two great stones are part of the Crown Jewels, held in trust by the monarch.
Gift, or Something Taken?
Not everyone tells the Cullinan's story the way the Royal Collection does. The Trust records, accurately, that the diamond was presented to Edward VII by the government of South Africa. Critics argue that a government installed under colonial rule, two years after a war Britain had won, could not give away the colony's wealth on behalf of its people — and that the indigenous population whose land the mine stood on was never consulted. Others point out that the Transvaal government was a forerunner of the South African state, that the gift was debated and voted on, and that the colony's representatives chose reconciliation. Both readings agree on the facts. They disagree on what the facts mean.
The argument flared again after the death of Queen Elizabeth II in 2022, when calls for the Great Star of Africa's return gathered thousands of petition signatures in South Africa, and again around the coronation of Charles III in 2023, when Cullinan I and II were on full display. The calls have not been backed by an official request from the South African government, and the stones remain in the Tower of London — carrying a question all along: who gets to give a country's largest diamond away, and who gets to ask for it back?
For now, the answer sits in the Jewel House, and on ceremonial days it leaves it — the sceptre at coronations, the crown at the State Opening of Parliament. The stone a mine manager mistook for a piece of glass still does the work it was cut for: the largest rough diamond ever found, cut into the largest colourless diamond ever cut, and never equalled since. Lumière Gems will keep following the stones whose stories, like the Cullinan's, turn out to be much larger than the stones themselves.