The 2.33-carat Winston Red diamond, one of the rarest pure red diamonds in the world, is now on display at the Smithsonian National Museum of Natural History. Its striking color comes not from chemical elements, but from intense heat and pressure deep within the Earth—making it an extraordinary geological wonder.
A Diamond Like No Other
Though it might resemble a ruby at first glance, the 2.33-carat Winston Red is actually a pure red diamond—a color so rare that scientists estimate only one in 25 million diamonds exhibits it. Now housed at the Smithsonian National Museum of Natural History in Washington, D.C., this extraordinary gem sits not far from the famed Hope Diamond.
Discovered to be among the rarest of its kind, the Winston Red was donated to the museum in 2023 by Ronald Winston, son of legendary American jeweler Harry Winston. Measuring about 8 millimeters in diameter, it is currently the fifth-largest confirmed red diamond in the world. Based on its antique cut, gemologists believe it was likely mined sometime before the mid-20th century.
Decades-Long Journey
The diamond’s known journey began in 1938 when it was owned by the Cartier family, who later sold it to the princely family of Jamnagar, India. Ronald Winston acquired it in the late 1980s, eventually passing it on to the Smithsonian.
To unlock its secrets, Gabriela Farfan, curator of gems and minerals at the Smithsonian, led a two-year scientific study. Published on June 6 in Gems & Gemology, the research traced the diamond’s potential geological origin to Venezuela or Brazil and classified it as a Type IaAB, Group 1 diamond.
The Science Behind the Scarlet Red
Unlike white, yellow, or blue diamonds, whose colors stem from trace elements, the red and pink hues in diamonds are caused by something far more complex: intense pressure and heat that deform the atomic structure. This deformation, known as "plastic deformation," occurs deep within Earth’s mantle. The misalignment in the diamond’s crystal lattice alters the way it interacts with light, resulting in its striking red appearance.
Winston Red is classified as a “Fancy Red” diamond—a term used when a diamond exhibits a pure red hue without any secondary tones like purple, brown, or orange. Less than 0.04% of naturally colored diamonds achieve this level of color purity.
Advanced Techniques Confirm Rarity
Researchers employed luminescence analysis, spectroscopy, and cathodoluminescence imaging to study the stone. These methods revealed clear bands of deformation and confirmed the geological conditions, precisely balanced pressure and temperature—that led to the formation of its unique red hue.
Now officially on exhibit since April 1, the Winston Red diamond not only dazzles visitors but also offers scientists a rare opportunity to study one of Earth’s most elusive mineral masterpieces.
(according to Popular Science, Smithsonian)