The Hope Diamond’s 45.52 sparkling, steely blue carats make it the most famous diamond in the world — shrouded in mystery and intrigue since it was pulled out of the ground in 17th-century India.
Scientists also look upon the diamond as a mysterious treasure, but for different reasons. Rather than a few centuries of legend and supposed curse, they would like to use it to study more than a billion years of the Earth’s history.
“It sort of gets lumped into this category of being really a piece of jewelry, a cultural icon, a cursed gem, whatever,” said Jeffrey E. Post, a geologist and curator at the Smithsonian Institution’s National Museum of Natural History, where the Hope Diamond is now on display for millions of visitors a year. “It has a natural history that goes way beyond its human history.”
This month, writing in the journal American Mineralogist, Dr. Post and his Smithsonian colleagues report the latest scientific tidbit about the Hope Diamond: It contains surprisingly high levels of the element boron.
Scientists already knew that natural blue diamonds had a smattering of boron. It gives them their color, and other unusual properties: The Hope, for example, glows orange-red when irradiated with ultraviolet light.
But other blue-diamond questions remain unanswered. For one, why are there any at all?
“If you go in your local jewelry store, they’re not blue,” Dr. Post said. “We’re talking maybe one out of millions of diamonds that are found each year that are in fact blue enough to be called a blue diamond.”
To better understand the blue diamonds, the scientists wanted to better understand the boron in them.
They placed 78 blue diamonds, including the Hope, in an apparatus that fired gallium ions, which peeled off atoms from a patch about one five-hundredth of an inch wide. These exfoliated atoms — hundreds of millions of them — were then sorted by weight to reveal how many were boron.
Even hundreds of millions of atoms correspond to only a few atomic layers, and the researchers tested other blue diamonds first to make sure that even under high-powered microscopes, no perceptible marks would be etched. “We don’t really want to have the Hope Diamond weighing less afterward than when it went in,” Dr. Post said.
Previous studies of blue diamonds had reported levels of boron of less than one in a million. But in parts of the Hope Diamond, boron levels were as high as eight per million atoms; in other parts, there was hardly any.
Curiously, diamonds with more boron were not necessarily bluer. “We tried to plot the intensity of the color versus the boron concentration,” said Eloïse Gaillou, the curator of the gem and mineral collection at the Natural History Museum of Los Angeles County and the lead author of the paper. “Basically, it gave no correlation at all.”
The boron data was intriguing, but ultimately the scientists would like to precisely count two versions of boron, one a slightly heavier isotope with an additional neutron. Rocks from the seafloor have more of the heavier boron than what is found in the earth’s mantle; that measurement would give strong clues to the origin of the boron.
Steven B. Shirey, a geochemist with the Carnegie Institution for Science in Washington, believes that the boron came from an ocean plate that was pushed downward near where the diamonds formed.
But to count the boron isotopes precisely would require a much longer experiment — days instead of hours — and that runs into logistical problem of conducting science on famous museum artifacts. “The public gets really surly when the Hope Diamond is not there on public display,” Dr. Post said.
So to perform their experiments on the Hope Diamond, the scientists had to pull all-nighters. After the museum closed, a jeweler removed the diamond from its ornate necklace setting to allow the scientists to make their measurements. It was returned to its display before the next morning.
Still, Dr. Post hopes the science shows that there is much more to the Hope Diamond than a curse.
“What this study, I hope, kind of reminds people,” he said, “is that it is also an incredibly interesting and perhaps almost unique scientific object.”