GIA Scientists Evaluate One of the World’s Rarest Diamonds

The Winston Red is now on public display at the Smithsonian Institution

CARLSBAD, Calif. – April 7, 2025 – A team of scientists from the Gemological Institute of America (GIA), collaborating with their colleagues from the Smithsonian National Museum of Natural History Department of Mineral Sciences and the curator from the Paris School of Mines, recently examined the Winston Red diamond – a very rare 2.33 carat red diamond which is now on display at the Smithsonian’s National Museum of Natural History in Washington, D.C. The Winston Red diamond is the fifth-largest diamond with an exceptionally pure red color known to exist and the only such red diamond on public exhibit.
 
“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. “Natural fancy-colored diamonds are very scarce, and red diamonds are exceedingly rare treasures of Mother Nature. Just two dozen pure red diamonds over one carat exist in the public record. Evaluating this spectacular gem is a scientific milestone for GIA and builds upon our expansive expertise in fancy-colored diamonds.”
 
Through careful analysis using advanced instrumentation and drawing on decades of research, experience and historical records, GIA scientists and their collaborators were able to determine the cause of the diamond’s rare color and its possible geographic origin, which is most likely Brazil or Venezuela, based on its mineralogical characteristics and history.
 
“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 executive vice president and chief laboratory and research officer. “The Winston Red diamond is a historic and very rare diamond; 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.”
 
“It’s as if the diamond was squeezed and now is intensely blushing,” said Dr. Ulrika D’Haenens-Johansson, senior manager of diamond research at GIA in New York City. “The reason why so few diamonds are red has eluded scientists for generations. Our detailed examination of the Winston Red, supplemented by data from other red diamonds evaluated over decades by GIA, uniquely positions us to probe this question. We can attribute the color to features introduced by plastic deformation – subtle changes to the diamond’s crystal structure caused by a long and stressful history under tremendous heat and pressure deep within the earth. The highly concentrated red color, along with its documented history makes this diamond extraordinary.”
 
“This gift by Ronald Winston of the Winston Red diamond and the Winston Fancy Color Diamond Collection is one of the most significant to the National Gem & Mineral Collection in recent decades. It is an honor for the Smithsonian to be the forever home for these natural history treasures, especially as a place where they can be enjoyed by the public,” said Dr. Gabriela A. Farfan, curator of gems and minerals at the Smithsonian Institution National Museum of Natural History in Washington, D.C. “Over the past two years, we have been working hard to study the Winston Red and get it ready for its big exhibit debut in the Winston Gallery, next to the Hope Diamond. The exhibit was inspired by the symphony, where the Winston Red acts as the conductor to a rainbow of other fancy color diamonds.”
 
Only one in ten thousand diamonds has a noticeable fancy color outside of the subtle color range normally associated with colorless diamonds. Of the more than one million colored diamonds examined by GIA, only 0.07% are red, and just over half of those received the coveted GIA color grade of ‘Fancy red’ given to the Winston Red.
 
The Winston Red is the centerpiece of a new exhibit of fancy color, natural diamonds that opened on April 1 at the Smithsonian’s National Museum of Natural History. The exhibit features 40 other gems from the Winston Fancy Color Diamond Collection, gifted to the museum by Ronald Winston, the son of distinguished jeweler and gem collector Harry Winston.
 
Dr. Farfan is the lead author and Dr. Ulrika D’Haenens-Johansson is a co-author of a scientific article on the Winston Red to be published this spring in Gems & Gemology, GIA’s quarterly scientific journal. The other co-authors are Russell C. Feather, II, collection manager for the National Gem Collection at the Smithsonian Institution; Dr. Eloïse Gaillou, director and curator of the Mineralogy Museum of Mines Paris – PSL (Paris School of Mines); Stephanie Persaud, a research associate at GIA; Dr. W. Henry Towbin, a postdoctoral research associate at GIA; and Dr. Daniel C. Jones, a research scientist at GIA. The article will be freely available, as are all issues of Gems & Gemology since 1934, on GIA’s website, www.gia.edu/gems-gemology.