Gemologists Uncover the Secrets Behind the Rarity of Red Diamonds

Red diamonds remain one of nature’s most elusive and captivating treasures. With only 24 specimens over one carat ever publicly recorded, their scarcity is legendary. Among them, the remarkable Winston Red has now taken centre stage at the Smithsonian National Museum of Natural History in Washington, DC.

This exceptional gem was donated in December 2023 by Ronald Winston, son of the renowned American jeweller Harry Winston. Weighing over one carat, the Winston Red is not only a visual marvel but also a scientific mystery—until now.

Recent research published in Gems & Gemology has provided unprecedented insight into what makes red diamonds so rare. Using advanced imaging and spectroscopic techniques, gemologists have identified that the Winston Red’s vivid crimson hue results from a combination of factors: a unique distribution of nitrogen impurities and a heavily deformed crystal lattice structure composed of tightly stacked red-to-pink layers.

These structural distortions—formed under extraordinary heat and pressure—are thought to alter the way light interacts with the diamond, giving rise to its intense red colour. Such conditions are extremely rare in the Earth’s mantle, further explaining the diamond’s scarcity.

Historical records trace the Winston Red as far back as 1938, when Jacques Cartier sold the stone to the Maharajah of Nawanagar. Combined with its cutting style and geological characteristics, the evidence suggests the gem likely originated from diamond-producing regions in Brazil or Venezuela.

For gemologists and collectors alike, the Winston Red represents both a scientific breakthrough and a pinnacle of natural beauty—an enduring reminder of the Earth’s ability to create something truly extraordinary.

Source: DCLA

One of the World’s Rarest Red Diamonds Goes on Display

The Winston Red, an extraordinary and exceptionally rare diamond, is now on show to the public — making it the only known pure red diamond of its kind currently on display anywhere in the world.

Weighing 2.33 carats, it holds the distinction of being the fifth-largest pure red diamond known to exist. To put that into perspective, fewer than two dozen red diamonds over one carat have ever been recorded, making this a truly exceptional stone.

It’s now on exhibit at the Smithsonian National Museum of Natural History in Washington, D.C., as part of a special showcase of natural coloured diamonds.

A team from the Gemological Institute of America (GIA), working alongside experts from the Smithsonian’s Department of Mineral Sciences and the Paris School of Mines, have conducted an in-depth examination of the gem.

GIA’s president and CEO, Susan Jacques, called the Winston Red “one of the most exquisite gems on Earth,” noting its intense deep-red colour and fascinating history. Red diamonds are incredibly rare, and among the more than one million coloured diamonds studied by GIA, a mere 0.07% were red — and just over half of those qualified for the elite ‘Fancy red’ grade awarded to the Winston Red.

Through advanced research, GIA scientists have identified the diamond’s colour origin and believe it likely came from either Brazil or Venezuela.

Tom Moses, GIA’s executive VP and head of research, shared his personal connection to the stone, having first examined it back in 1987. He recalled its striking deep red hue and historical significance — a diamond once sold by Jacques Cartier in 1938 to the Maharaja of Nawanagar.

The Winston Red is now the star attraction in a new exhibition at the Smithsonian, which features 40 other rare coloured diamonds from the Winston Fancy Color Diamond Collection. The collection was donated by Ronald Winston, son of legendary jeweller Harry Winston.

This exhibition is a rare opportunity to witness one of nature’s most elusive and captivating treasures — a true celebration of colour, history, and craftsmanship.

Source: DCLA