Here’s what you’ll learn when you read this story:

• The Cullinan diamond was once the largest uncut gem-quality diamond ever discovered, and today its cut and polished pieces adorn priceless royal regalia.
• This behemoth of a diamond was found when a mine supervisor in South Africa noticed something glinting in a shaft wall. Then its journey began.
• Protected by a mirage of fancy locked cases and military fanfare, the Cullinan actually traveled to London in a plain box, and to Amsterdam in the jeweler’s own pocket.

Millennium Star. Koh-I-Noor. Excelsior. Hope. Centenary. Diamonds of extraordinary value and renown. And though its road to sparkle and stardom was anything but glamorous, the Cullinan Diamond deserves to be mentioned right alongside these other priceless gems.

Back in January 1905, the Premier Mine near Pretoria, South Africa was a trove of diamonds just waiting to be discovered. Superintendent Captain Frederick Wells was carrying out his daily inspection of the mine 18 feet down when he caught a flash of light. Wells pulled out his pocketknife, used his blade to dig into the shaft wall, and discovered what he at first thought was a shard of glass left there as a practical joke. It turned out to be a rock unlike anything he’d ever seen.

What Wells had found turned out to be the largest gem-quality diamond on Earth. At 1.37 pounds (621 grams), what would eventually become known as the Cullinan diamond—named for the owner of the mining company—was 3.97 inches long, 2.5 inches wide, 2.3 inches deep, and weighed an astounding 3,106 carats. The mine owners sold it to the South African Transvaal Colony government for $203,000 in 1907 (over 7 billion dollars today), and the government decided that the diamond belonged in the hands of King Edward VII.

The diamond’s size, bluish cast, and incredible clarity instantly made it a future royal heirloom, and it was presented to Edward VII on his birthday in the wake of the Second Boer War, as a tribute to five years of peace. But to do that, the diamond needed to be transported to London safely, without thieves turning the operation into a jewel heist.

Transporting the diamond safely meant figuring out how to divert the eyes of the press during its secret passage across the ocean. As reporters hunted for details, the colonial government hired armed guards and military personnel with much fanfare. What the media never realized, however, was that the entire thing was an elaborate decoy. While the Cullinan diamond’s supposed guardians boarded a ship to London, the diamond itself was actually being shipped in a plain box hidden amid a normal shipment of packages.

The diamond landed in London safely, but after it was presented to King Edward VII in 1908, he was told that it couldn’t be cut and polished as it was. It would need to be divided into smaller pieces for that to be possible, which again demanded that the diamond make a journey to another country, this time to Amsterdam in the Netherlands. So the king had the uncut diamond insured to the tune of the $49.4 million it was then worth (the various gems it was eventually cut into are today estimated to be worth several billion dollars collectively) and put this undertaking into the hands of M.J. Levy & Nephews. Eventually, the stone would go to renowned jeweler Joseph Asscher at the Royal Asscher Diamond Company in Amsterdam.

Journalists once again swarmed when the Cullinan diamond reportedly boarded a Royal Navy ship in a sealed box. They were unaware, however, that this box was empty. This time, Asscher’s brother, Abraham, carried the diamond in his coat pocket during the trip across the North Sea. The Cullinan eventually landed safely at company headquarters, where Joseph Asscher took over, analyzing the diamond before making an embarrassingly public attempt to cut the stone that ended in his cutting tool breaking. After reinforcing his tools, Asscher succeeded in privately cutting the gem in two (with no one but a Notary Public present).

After initially being cut into two pieces of 1,997 and 1,040 carats respectively, the diamond was eventually divided into a total of nine main stones, 96 smaller gems, and a handful of polished leftovers. The leftover fragments were Asscher’s payment, which he would eventually incorporate into family bridal jewelry that still survives today. As for the rest of the Cullinan, King George V had the two largest pieces, Cullinan I and II, set in the Sovereign’s Scepter and the Imperial State Crown after Edward VII’s death. He later bought Cullinan VI and VII from Asscher as a gift to Queen Alexandra. These (and the Cullinan III and IV, which belonged to Queen Mary) were passed down to Queen Elizabeth II at her 1953 coronation.

The final phase of the Cullinan diamond’s metamorphosis is now on display with the rest of the Crown Jewels in the Tower of London. Cullinan I, also known as the “Great Star of Africa,” is the literal jewel of the royal crown. It weighs 530.2 carats and reflects light from 74 facets. The “Smaller Star of Africa” joins thousands of brilliant-cut diamonds (along with rubies, sapphires, and pearls) on the royal scepter. Cullinan III is slightly more obscure, but this pear-cut gem ended up as a brooch for Elizabeth II, which she wore alongside Cullinan IV when she met with Joseph Asscher’s brother, Louis, in 1958.

“Here, Mr. Asscher, you can take them in your hands,” she said, even as he struggled to believe what he was witnessing with his failing eyesight. “You held them in your hands before!”