Was the Cullinan Diamond a Royal Gift or Stolen Gem?

Named the Cullinan diamond after Thomas Cullinan, the owner of the Premier Mine, it was — and still remains — the largest gem diamond ever found. In its uncut state, it weighed 3,106 carats and measured roughly 4 inches by 2.5 inches by 2.3 inches (10.1 by 6.35 by 5.9 centimeters). For comparison, the blue-hued Hope Diamond weighs a little over 45 carats.

The rough stone was gifted to King Edward VII in 1907 (more on that transaction in a minute) and cut into nine major diamonds named Cullinan I through IX, ranked from largest to smallest.

The Cullinan I, also known as the "Great Star of Africa," is the largest colorless cut diamond in the world. It weighs more than 530 carats and is mounted on the Sovereign's Scepter, part of the British royal family's priceless crown jewels. The Cullinan II, no slouch at 105.6 carats, is the second-largest cut diamond in the world and is the sparkling centerpiece of the family's Imperial State Crown.

The Cullinan diamonds are not only some of the world's largest cut diamonds, but they're also some of the most beautiful, possessing all of the most-prized characteristics of gem diamonds, says Evan Smith, a senior research scientist at the Gemological Institute of America (GIA), the organization that grades diamonds according to the "four Cs": cut, clarity, color and carat weight.

"The Cullinan diamonds are the ultimate color, they're very large and their clarity is very good," Smith says. "They're the quintessential top tier in terms of what makes an attractive diamond — something that's completely colorless and nearly transparent inside."

When Queen Elizabeth II was laid to rest in 2022, Cullinans I and II were on prominent display. Both the scepter and the crown (and a third bejeweled object called the Sovereign's Orb) were placed on the Queen's casket during the funeral procession, which was broadcast live around the world.

While heads of state paid their respects to Elizabeth for her dignity, strength and poise during her historic, nearly 71-year reign, others criticized the Queen for never formally apologizing for atrocities committed during Britain's colonial era, which included colonial rule over part or all of South Africa from 1795 to 1961. The discovery and sale of the record-setting Cullinan diamond is wrapped up in that messy colonial history.

The Premier Mine, where the Cullinan was discovered, was located in an area formerly known as the Transvaal. In the early 19th century, Dutch settlers called Boers fled the British-controlled Cape Colony and trekked to the hot, dry interior of South Africa near modern-day Pretoria. There, the Boers defeated local tribes and founded the Transvaal Republic.

In 1867, a 15-year-old boy named Erasmus Jacobs, son of a poor Boer farmer, found a shiny rock on his otherwise desolate land. When neighbors convinced him to send the rock to British authorities in the Cape Colony, tests confirmed that the brownish-yellow stone was in fact a 21.25 carat diamond now known as the Eureka Diamond.

"This diamond," wrote the British Colonial Secretary at the time, "is the rock upon which the future success of South Africa will be built."

The discovery of diamonds in the Transvaal drew a flood of prospectors to the region. Fifteen years later, they also discovered gold there. The British, who had signed treaties recognizing Boer independence in the 1850s, turned around and annexed the Transvaal and other Boer territories. After two bloody conflicts known as the Anglo-Boer Wars, the British prevailed and claimed the Transvaal as part of the Crown's colonial holdings in South Africa.

Thomas Cullinan, a British citizen born in South Africa, bought the land for the Premier Mine in 1902, the year the Boers ceded the Transvaal to the British. When the remarkable Cullinan diamond was discovered there in 1905, the government of British-controlled Transvaal bought it from Cullinan in 1907 for £150,000 British pounds (the equivalent of £20 million pounds today or $22 million) and presented it as a birthday gift to King Edward VII, who reluctantly accepted it "as a token of the loyalty and attachment of the people of Transvaal."

The Cullinan diamonds that adorn the Sovereign Scepter and the Imperial State Crown are usually kept behind bulletproof glass in the Tower of London, where the crown jewels are on display for tourists. But something about seeing these incredibly valuable objects — the Cullinan I alone is worth an estimated $400 million — riding along with the Queen's funeral procession fired up critics of Britain's colonial past.

"It is clearly way past time to repatriate all these grisly reminders of empire as part of a broader reparations effort," journalist Helena Cobban wrote Sept. 24, 2022. "How many new houses, roads and bridges might be built... from the sale or repatriation of just a few of these gems?"

Everisto Benyera, a professor of African politics at the University of South Africa, called into question the legitimacy of the British Transvaal government, which had forcibly taken the land from the Boers, who themselves had stolen it from African tribes.

Of King Edward VII and the rest of the royal family, Benyera told CNN, "Receiving a stolen diamond does not exonerate the receiver. The Great Star [of Africa] is a blood diamond."

GIA's Smith made headlines in 2016 when he and his colleagues published groundbreaking findings in the journal Science showing that very large and strikingly clear diamonds like the Cullinan are formed hundreds of miles deeper inside Earth than 99 percent of the world's gem diamonds.

"Diamonds are already an incredibly unique geological material," Smith says. "Yet even within the realm of diamonds, diamonds like the Cullinan are a special category that form in a slightly different way and have their own really unique properties."

Almost all the standard diamonds that adorn engagement rings and earrings are formed around 90 to 125 miles (150 to 200 kilometers) below the surface in the lithosphere, which corresponds to the base layers of the thickest sections of continental plates. At GIA, Smith was able to examine much rarer and more expensive diamonds called CLIPPIR diamonds, an acronym for the qualities of these prized gems: Cullinan-like, large, inclusion-poor, pure, irregular and resorbed.

Inclusions are tiny specks of minerals trapped inside diamonds that affect their clarity. CLIPPIR diamonds like the Cullinan have almost no inclusions, but by examining the few impurities he could find in hundreds of large diamonds, Smith concluded that CLIPPIRs formed at depths closer to 410 miles (660 kilometers) where liquid metal churns inside Earth's mantle.

"Super-deep" diamonds like the Cullinan are thrust to the surface and mixed with shallower diamonds during a particularly deep and explosive type of volcanic eruption known as a "Kimberlite" eruption. Kimberlite magma, named after the South African city Kimberley, contains more water and CO2 than regular magma.

"It's almost like shaking a Champagne bottle and releasing all of that pressure," Smith says. "That's the kind of energy we're talking about."

All of the biggest and clearest diamonds in the world have been recovered from Kimberlite deposits, many of them in South Africa, but also in Brazil and India, the source of the fabled Koh-i-Noor diamond. The 105-carat Koh-i-Noor, which means "Mountain of Light" in Persian, was taken from India by the British in the 19th century and also became part of the crown jewels.

As with the controversial Cullinan, the Queen's death prompted renewed calls for the Koh-i-Noor to be repatriated to India.