How a Smithsonian Curator Discovered the Hope Diamond’s Many Secrets

The storied past of the 45.52-carat sapphire-blue gemstone hails back to the days before the French Revolution

Hope Diamond
The Hope Diamond was cut from Louis XIV’s “French Blue." Chip Clark/National Museum of Natural History

Evalyn Walsh McLean knew how to throw a party. Every A-list ambassador, dignitary, politician or world leader made the guest lists at the parties thrown by the Washington, D.C. socialite who spared no expense and who owned and wore the most famous diamond in the world—the 45.52-carat sapphire-blue Hope Diamond. McLean was rich, famous and fortunate, and she never minded that the gem allegedly carried a curse.

She had married Edward Beale McLean (also rich) in 1908, and three years later the couple purchased the stone, which was cut from Louis XIV’s “French Blue,” for a cool $180,000 (equivalent to about $5.8 million in today’s dollars). After McLean died, the Hope, along with its 46-diamond necklace chain, was bought from the McLean estate by famed jeweler Harry Winston. In 1958, after touring it in his exhibition “The Court of Jewels,” he shipped the dazzling blue diamond to the Smithsonian via U.S. mail. The Smithsonian even kept the box it arrived in.

The Object at Hand

This authoritative guide delivers in-depth reportage on the history of remarkable objects from the Smithsonian's collections.

Today, the dazzling blue diamond occupies one of the most hallowed grounds at the Smithsonian’s National Museum of Natural History. Armed guards stand at the entrance to its high-security chamber. Inside, the gem is housed in a glass case that is also an impenetrable vault. Each night after visitors have left for the day, the diamond is mechanically lowered into the pedestal of the case for safe storage.

Jeffrey Post, the museum’s now-retired curator of gemstones, dedicated nearly four decades at the Smithsonian to the study of the Hope Diamond, and his curriculum vitae is studded with publications on this, his favorite topic. Post traced the history of the gemstone, tracking it from its origin point in India to a gem dealer who in 1668 sold it to Louis XIV, and its subsequent cutting into the “French Blue” to its current iteration, hung as a pendant on a necklace designed by Pierre Cartier in the 20th century.

At the time of the French Revolution, the historic gem was stolen, disappeared and then rediscovered. Each time the diamond made its appearance it was cut into a smaller stone for reasons of aesthetics or, in one case, to cover up a crime. And it is because of the ongoing scholarship of Post and his colleagues that we now understand much of how the diamond traveled from one hand to the next, how it was cut and who owned it.

Post’s work has shown that the diamond is much more than a pretty bauble—its magnificent blue, the azure color of the deep sea, is extremely rare, occurring in only one out of every several hundred thousand diamonds. “Its creation, as far as we know, is a completely unique event in the history of the earth,” Post said in 2010, when he was studying the diamond’s unusual coloration.

He learned that it was caused by a varying concentration of boron that ranged from zero to eight parts per million, making the Hope more of a mosaic of blues. Post also learned that under an ultraviolet light, the Hope phosphoresces, glowing orange for about a minute or so. Woe unto any thief hoping to make off with the priceless gem, because a spectrometer can measure the light spectrum and pick up the gem’s “fingerprint,” a telling imprint that differs from one diamond to another.

In 2014, Post with his colleague and partner, François Farges, a mineralogist at the French National Museum of Natural History in Paris, created a computer simulation of what the Hope Diamond would have looked like when it was owned by Louis XIV, who took on the grandiose title of Sun King. Through meticulous analysis and a delightfully impulsive discovery made by Farges, the pair figured out that the king had a very unusual way of displaying the diamond. The revelation was initially sparked when Farges noticed a peculiar specimen, made of lead, in the Paris museum’s collections. It was just happenstance that he came across it and had the forethought to compare it to drawings of the famous stolen French Blue. It turned out that this lead specimen was an exact replica—a cast made from a mold of the lost French Blue diamond.

With digital 3D measurements, he and Post were soon looking anew at the Hope, which had long been believed to have been cut from the French Blue. “It fit into the French Blue perfectly,” Post revealed in 2014. “You could see exactly how [it] was cut to form the Hope.”

That right there could have been the career high point for the two scholars, but the diamond-detective duo went on to figure out why the French Blue was cut in a most peculiar way: not to simply enhance its brilliance as a gemstone, but so that light would travel straight through certain facets and out the back of the stone. It was unusual and beyond the norm for how jewelers of the period would have cut diamonds.

Farges and Post revealed that the king’s jeweler had intended for the center of the stone to act much as a window. A 1691 note in the inventory of the French crown jewels indicated that the gemstone was “set into gold and mounted on a stick.”

With computer modeling, the pair replicated the trick. The result was that when the French Blue was placed before gold metal backing, its unique window revealed at the center of the magnificent blue stone a brilliant gold sun, dazzling to the eye. “Louis XIV was the ‘Sun King,’ and so this would have been an emblem representing his power,” said Post. “His colors were blue and gold, and so to have a blue diamond with a gold sun in the center—that’d be something that no one else has, something that would almost seem divine.”

And to think that Evalyn Walsh McLean, millionaire dilettante owner of the historic Hope Diamond from 1911 to 1947 playfully hung that glorious gemstone around the neck of her dog.

This story, and so many more, are featured in a new book out this month from Smithsonian Books: The Object at Hand: Intriguing and Inspiring Stories From the Smithsonian Collections. The volume explores artworks, scientific specimens, historical artifacts, airplanes, spacecraft, plants and other objects, contemplating how each item represents different facets of humanity and resonates with cultural poignance in surprising ways.

Get the latest on what's happening At the Smithsonian in your inbox.