If you gaze into the Winston Red Diamond long enough, it almost seems to burn. The 2.33-carat gem gleams a deep, saturated crimson, as if the Earth itself bled light into its facets.
This tiny stone is an anomaly of geology. It is the rarest kind of diamond — graded “Fancy red,” pure and unmodified by other hues. There are fewer than 30 like it known to science. This one shines bright at display at the Smithsonian’s National Museum of Natural History, where it’s housed right next to the famed $350-million Hope Diamond.
But, for decades, even as it passed through royal necklines and celebrity fingers, no one truly understood what made the Winston Red red. Now, thanks to a meticulous investigation by scientists at the Smithsonian and the Gemological Institute of America, its secrets are finally out. What they found tells us not just about the stone’s peculiar glow, but also about the impossible pressures that created it — and the long, uncertain journey it took to reach the light.
A 2.33 Carat Mystery Gem
Unlike other colored diamonds, red diamonds don’t owe their hue to chemical impurities. There’s no boron to make them blue, no nitrogen for yellow. Pure diamonds are only made of carbon. So, the Winston Red is crimson for a stranger reason. The crushing pressures and blistering temperatures deep within the Earth twisted its atomic lattice just enough to change how it interacts with light.
This process, called plastic deformation, leaves behind invisible scars in the diamond’s crystal structure. These distortions create optical effects that bend and absorb light in unusual ways, especially around a wavelength of 550 nanometers — the sweet spot for red.
“The Winston Red owes its pure crimson color to a careful balance of absorption features,” the researchers write in their study published in the journal Gems & Gemology. These include the key 550 nm band linked to plastic deformation, as well as other nitrogen-related defects known by the cryptic names N3, H3, and H4.
Notably, the Winston Red shows no modifying hues—no brown, orange, or purple. That earned it the coveted “Fancy red” classification, a label so rare that it appears in fewer than one in every 25 million diamonds analyzed by the Gemological Institute of America (GIA).
From Empire to Exhibit
The story of the Winston Red begins in September 1938, in the London offices of the Cartier family. Jacques Cartier himself sold the stone—then known as the “Raj Red”—to Digvijaysinhji, the Maharaja of Nawanagar. In a letter from that year to the maharaja, Cartier imagined the diamond set in a ring or “put in your big necklace between the green diamond and the pink diamond pendeloque […]. The red diamond would take the place of the white triangular diamond.”
That necklace, known as the Ceremonial Necklace of Nawanagar, was one of the most extravagant pieces Cartier ever created: over 600 carats of diamonds, including legendary stones in green, blue, and pink. The red diamond was eventually set into the necklace, as confirmed by 1947 photographs showing the Maharaja holding the piece, the ruby-red gem glowing at its center.
The necklace was dismantled in the 1960s, and the red diamond disappeared from public view — until 1988, when Ronald Winston, heir to the House of Winston, purchased it from the Maharaja’s son. The diamond was briefly dubbed the “Raj Red” again and made its debut at a 1989 Tokyo event, worn as a pinky ring by actress Brooke Shields.
In 2023, Ronald Winston donated the gem to the Smithsonian. It was renamed the Winston Red and now sits in the museum’s Winston Gallery, surrounded by 40 other stones from the Winston Fancy Color Diamond Collection.
Tracking Origins in the Stone
The Winston Red’s journey through human hands is well documented. Its geological origin, however, remains elusive.
The diamond’s cut — an old mine brilliant with a large culet and thin girdle — suggests it was mined and fashioned before the mid-20th century. Its internal features place it in a category known to gemologists as a type IaAB Group 1 diamond. This group includes most red and pink diamonds that are heavily deformed but rich in aggregated nitrogen, particularly B-center nitrogen defects.
By comparing the Winston Red’s structure and spectroscopic fingerprint to hundreds of other Fancy red diamonds, the team narrowed its likely origin to either Brazil or Venezuela. These countries have known deposits that could produce diamonds under the extreme conditions necessary for this kind of color transformation. Yet even here, mystery endures.
“The geographic origin of the Winston Red diamond remains unknown,” the authors concede. “The geology of these specific areas has scarcely been studied.
And as rare as Fancy red diamonds are, the Winston Red is rarer still. Among GIA’s database of over a million fancy-color diamonds, only 0.04 percent received the Fancy red grade. Of those, just 4 percent weigh more than two carats. Most have low clarity scores, with inclusions, chips, and feathers — flaws that would lower the value of other gems but are forgiven in red diamonds because of their extraordinary rarity.
“Lower clarity in Fancy red diamonds is of little concern compared to the coveted red color,” the GIA notes in its study.
The Winston Red has an I2 clarity rating, due to internal feathers and chips around the girdle. But its color is so visually overpowering that few would notice.
A Unique Gem Now for Public Viewing
Its size places it second only to the 5.11-carat, $7-million Moussaieff Red among confirmed Fancy red diamonds in public records. But unlike the Moussaieff, which is privately held, the Winston Red is now available for anyone to see in the heart of the nation’s capital.
“This donation to the museum represents my life’s achievements in this domain,” said Ronald Winston. “And I am so happy to share this collection with the Institution and the museum’s visitors.”
Diamonds have always held our attention, but Fancy reds are in a league of their own. Their beauty is matched only by their scientific significance.
“These gems give us the opportunity to share with our visitors the full range of colors in which diamonds occur,” said Gabriela Farfan, the museum’s curator of gems and minerals.
And with the Winston Red now open to the public, scientists and laypeople alike can marvel at a gemstone forged by time, pressure, and chance — a rare red heartbeat in the stone skeleton of the Earth.
