Epic Diamonds

The Hope Diamond: The History and Science of the Priceless Blue Gemstone

Dr. Sally Eaton-Magaña of GIA gets unprecedented access to the famous diamond.

hope diamond
The 45.52 carat Hope Diamond at the Smithsonian National Museum of Natural History. Photo Credit: Marvin Joseph/The Washington Post

A gemstone of legends, kings—and superstitions—, the Hope Diamond is one of history’s most famous diamonds. This 45.52 carat fancy deep grayish-blue diamond has an incomparable history and an extraordinary combination of physical properties.  During its long history, it has intersected with the French monarchy—Kings Louis XIV through XVI—, and likely the British monarch King George IV.  It has been owned by wealthy merchants and some of the most well-known individuals within the jewelry world, including Pierre Cartier and Harry Winston. 

“A tiny fragment of midnight sky, fallen to earth and still aglow with star gleam.”

Washington Post, 1947
hope diamond
The Hope Diamond is 45.52 carats with a fancy deep grayish-blue color. Photo Credit: Smithsonian Institution

A Closer Look at the Hope Diamond

In 2005, I was fortunate to be part of a research team that documented and researched the Hope Diamond’s red phosphorescence, which was previously observed many times before, yet never fully investigated. Those heady days were an exciting opportunity for me; it was enthralling to hold this singular stone and come so close to its incomparable story.

hope diamond
Dr. Sally Eaton-Magaña with the Hope Diamond. The diamond was taken off display for research within the back rooms of the Smithsonian’s National Museum.

The History of the Hope Diamond

The Hope Diamond got its name from one of its first documented owners, Henry Philip Hope, a wealthy British banker and an avid collector of gems and paintings. Included among Hope’s holdings when he died, the diamond was passed down through this family until 1901 when it was sold to a jeweler. Then, it traded hands several times until it was bought in 1912 by Evalyn Walsh McLean, a Washington, D.C socialite, who owned it until her death in 1947. Harry Winston owned it for the next eleven years until he donated the Hope Diamond to the Smithsonian Institution in 1958. Now, the gem belongs to all Americans.

So how did the story of this illustrious diamond begin? It all goes back to the Tavernier Blue, a 115 carat blue diamond that was brought from India to France, and purchased by the “Sun King”, King Louis XIV, in 1673. The stone was re-cut by his royal jeweler into the 69 carat French Blue, and fashioned with a gold backing that allowed the “sun” to shine within is central field of blue.

hope diamond science
Photosimulation of the 69 carat ‘French Blue’ diamond with a gold backing that was part of the French Crown jewels for King Louis XIV, the Sun King. Farges et al., Europhysics News, Vol. 43, No. 1, 2012; The rediscovery of the ‘French Blue’ diamond (europhysicsnews.org)).

This beautiful blue diamond was stolen during the French Revolution in 1792. Twenty years later, a smaller (although still spectacular) 45 carat blue diamond surfaced in London. This diamond, which ultimately became known as the Hope Diamond, appeared just days after the twenty-year statute of limitations for crimes committed during the French Revolution had passed. However, there is little information about who might have done the re-cutting of the gemstone. Although it had been speculated for decades that the lost French Blue and the Hope Diamond were actually the same stone, convincing evidence was not presented until the mid-2000s. 

Read More: The Science of Colored Diamonds

Realistic replicas of the 115 carat Tavernier Blue (the original blue diamond that was presented to King Louis XIV) and the 69 carat French Blue were created. Computer models were produced of all three diamonds to verify that the Hope could be wholly contained within the French Blue. Some of the cutting decisions of the Hope Diamond, such as its asymmetric shape, were best explained by its prior history as the 69 carat French Blue. 

hope diamond science
These computer models show the Hope Diamond nested inside the French Blue and the Tavernier Blue and provides the most convincing evidence to date that the Hope Diamond derived from the French crown jewel. Photo Credit: Museum Diamonds.

So what was so special about the Hope Diamond that it attracted such prestigious and royal attention? Well, for starters, the Hope Diamond was graded by the GIA in 1988 and in 1996 as a 45.52 carat diamond with a cushion shape with antique brilliance, VS1 clarity and a Fancy Deep grayish-blue color (the result of an incredibly high concentration of observable boron impurities determined as about 1.7 parts per million). 

hope diamond gia grading report
Excerpt of the GIA diamond grading report (# 5230103) issued in 1988. The color for the Hope Diamond was described as Fancy Deep grayish blue in an updated report in 1996.

The vast majority of natural gem diamonds (about 99%) have high amounts of nitrogen impurities, with the remaining 1% having little-to-no detectable nitrogen. Less than 0.1% of diamonds—including the Hope—have detectable boron; among these, the vast majority have lower quantities of boron than the Hope Diamond, with most ringing in with less than 0.5 parts per million.  Therefore, any natural diamond with such a high quantity of boron is exceedingly unusual, and the occurrence within such a large diamond is truly rare.

Another extraordinary trait of the Hope Diamond is its fiery red phosphorescence. When the diamond is exposed to ultraviolet (UV) light, the diamond will glow like a burning ember for longer than a minute. Like the diamond’s blue color, the red phosphorescence is also related to the boron that was incorporated into the diamond while the gemstone formed. When exposed to short-wave UV, those boron atoms interact with other impurities within the diamond that cause the gemstone to emit visible light. The vibrant red glow, coupled with its extended duration, makes this trait quite distinctive for the diamond.

hope diamond
The Hope Diamond glows a fiery red when exposed to short-wave UV light. It excited phosphorescence bands located at 500 nm and 660 nm. Photos by Chip Clark and John Nels Hatleberg

Though superstition and suspicions of a curse have surrounded the history of Hope Diamond for decades, scientific examinations of the diamond—particularly over the last twenty years—have exposed many of its long-held secrets. Such recent research endeavors include the computer modeling that convincingly demonstrated its origin as the French Blue, spectroscopic details and origins of its phosphorescence, plus determination of both its total boron concentration and its observable boron concentration.

harry winston holding the hope diamond
Harry Winston displays some of the gems in his collection in the palm of his white-gloved hand, including the Sapphire of Catherine the Great (next to thumb), the Hope Diamond (between index & middle), the Royal Spanish Emerald (green), the Idol’s Eye (left of emerald), the Jonker Diamond (C, square cut), the Star of the East diamond (tear shaped, bottom), a large ruby and a pair of 50-carat matched pear shaped diamonds. (Photo by Bernard Hoffman/The LIFE Picture Collection/Getty Images)

Although this diamond passed through many hands before arriving at the Smithsonian where it will continue to captivate millions of visitors, it is fortuitous that this gemstone found its name from one of the first documented owners—Hope. The concept of hope is a universally human sentiment and a fitting appellation for this priceless gem.

Gemological Institute of America