Before the Winston Red Diamond took its place as the dazzling centerpiece of a new exhibit at the Smithsonian’s National Museum of Natural History in Washington, DC, on April 1, the ultra-rare, 2.33-carat gem underwent one of the most thorough scientific evaluations ever conducted on a "Fancy red" diamond.
The examination was a collaborative effort between Gemological Institute of America (GIA) experts, Smithsonian mineral scientists and a curator from the Paris School of Mines. The team applied decades of research and cutting-edge instrumentation to analyze the diamond’s structure, color origin and geographic source.
“The Winston Red diamond is one of the most exquisite gems on Earth, from its unparalleled deep-red color to its rich history,” said Susan Jacques, GIA president and CEO. “Evaluating this spectacular gem is a scientific milestone for GIA and builds upon our expansive expertise in fancy-colored diamonds.”
Red diamonds are famously rare — less than one in 25 million diamonds receives a Fancy red grade. Of more than one million colored diamonds analyzed by GIA, only 0.07% are red, and fewer still qualify as Fancy red with no secondary hue. The Winston Red is the fifth-largest Fancy red diamond ever recorded and the only one of its kind currently on public display.
“When the Winston Red was recently submitted to GIA for grading, I immediately recalled examining it in 1987 — it is an unforgettable diamond,” said Tom Moses, GIA’s executive vice president and chief laboratory and research officer. “Its old mine cut, deep red hue and inclusions tell a story that can be traced back to September 1938 when Jacques Cartier sold the stone to the Indian Maharaja of Nawanagar.”
The diamond’s striking color and complex internal structure were of particular interest to researchers.
“It’s as if the diamond was squeezed and is now intensely blushing,” explained Dr. Ulrika D’Haenens-Johansson, senior manager of diamond research at GIA.
Her team determined that the Winston Red’s vivid red coloration is the result of plastic deformation—microscopic distortions in the diamond’s crystal lattice formed under extreme heat and pressure during its formation deep within the Earth.
Unlike other colored diamonds that owe their hues to trace elements in their chemical composition, red diamonds are colored by structural changes caused by immense geological stress. These same conditions often result in significant internal fractures. The Winston Red has an I2 clarity grade, reflecting visible inclusions, but these are characteristic of red diamonds and do not detract from its extraordinary value or rarity.
Mineralogical and historical evidence suggest the Winston Red likely originated in Brazil or Venezuela, further enhancing its mystique. Interestingly, the world's largest faceted Fancy red diamond — the 5.11-carat Moussaieff Red — was discovered in Brazil in 1989. Other regions known to produce red diamonds include Western Australia and South Africa.
“This gift by Ronald Winston is one of the most significant additions to the National Gem & Mineral Collection in recent decades,” said Dr. Gabriela Farfan, the Smithsonian’s curator of gems and minerals. “We’ve been working closely with GIA over the past two years to study and prepare the Winston Red for its debut.”
Now on display in the Smithsonian’s Winston Gallery — just steps from the famed Hope Diamond — the Winston Red acts as the conductor of a “symphony” of 40 other fancy color diamonds, all part of Ronald Winston’s extraordinary donation.
Credits: The 2.33-carat Winston Red diamond. Photo by Robert Weldon, courtesy of Ronald Winston. The Winston Red (center) is shown alongside two other colorful diamonds included in the Smithsonian exhibit: the “red-brown” "DeYoung Red" (left, 5.03 carats) and the DeYoung Pink (right, 2.82 carats). Photo by Dr. Gabriela Farfan.