Why does the Hope Diamond glow red in UV light?

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The Hope Diamond intrigues people with its beautiful blue color, its mysterious curse, and its sheer size. But did you know it glows "like a coal on a barbecue grill" for several minutes after it has been exposed to UV light? Learn the scientific secrets of the glowing blue diamond.

The Hope Diamond was originally found in India, made its way into the possession of several Kings of pre-revolutionary France, was lost in the Revolution but turned up in England, and then made its way — via the Robber Barons — to America and the Smithsonian. Considering the diamond was around since the 1600s and worn by the type of people who played for high stakes, it's no surprise that many of its owners met bad ends. Perhaps the fact that some of those ends could be described with the words "torn to shreds" resulted in what was called "The Curse of the Hope Diamond." But there's a much more solid and readily testable mystery associated with the diamond — when exposed to strong UV light it glows bright red.

Gemstone experts are naturally reluctant to allow the diamond to be cut up for research. Recently though, researchers carefully tested the phosphorescent spectra of several blue diamonds to try to see a pattern. They learned that other blue diamonds, especially ones of greater size, also glow red when exposed to UV light. Most diamonds have nitrogen impurities inside them, as well as natural cavities. Both influence the color, but only blue diamonds have boron inside them.


Scientists believe that when the stone is exposed to bright ultraviolet light, the boron and nitrogen interact and phosphoresce, giving off a certain quality of red light. When scientists treated colorless diamonds with boron, they turned blue, but they didn't give off the same color light under UV radiation. Although the mystery isn't solved, this does give diamond experts a way to know if a blue diamond is natural or made by humans.

And, we are pleased to report, that none of the research team was torn to shreds.


Top Image: 350zz33. Via The Smithsonian.