Supplier News: Week of April 7

By Brittany Siminitz | April 09, 2025

GIA Evaluates the Winston Red Diamond

The Winston Red, the fifth-largest diamond with an exceptionally pure red color known to exist, was recently evaluated by a team of scientists from GIA prior to going on display at the Smithsonian National Museum of Natural History in Washington, D.C.

“Just two dozen pure red diamonds over one carat exist in the public record,” said Susan Jacques, GIA president and CEO, in a statement. “Evaluating this spectacular gem is a scientific milestone for GIA and builds upon our expansive expertise in fancy colored diamonds.”

Weighing 2.33 cts., the Winston Red was gifted to the Smithsonian by Ronald Winston, son of distinguished jeweler and gem collector Harry Winston. It is the only pure red diamond on public display anywhere in the world.

“The Winston Red diamond is one of the most exquisite gems on earth, from its unparalleled deep red color to its rich history,” Jacques said. “Natural fancy colored diamonds are very scarce, and red diamonds are exceedingly rare treasures of Mother Nature.”

Utilizing advanced instrumentation, historical records, and decades of research, GIA scientists and their collaborators were able to determine the cause of the diamond’s rare color and its possible geographic origin—likely Brazil or Venezuela—based on its mineralogical characteristics and history.

“When the Winston Red was 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, in a statement. “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.”

On April 1, a new exhibit of natural fancy colored diamonds, with the Winston Red as its centerpiece, opened at the Natural History Museum’s Winston Gallery, home of the Hope Diamond (which was donated to the Smithsonian by Harry Winston in the 1950s).

Top: The Winston Red diamond (photo by Robert Weldon)