Why the deep-blue Hope Diamond glows red  

Washington, January 9: An expert at the United States Naval Research Laboratory (NRL) has unearthed the reason why the deep blue Hope Diamond exhibits a red glow for several seconds, and looks like a fiery coal, upon being bathed in ultraviolet light.

Gem researcher Sally Magana says that the legendary 45.52-carat diamond, which sits centre stage in the Smithsonian Institution's United States Gem Collection, emits far less green-blue light when bathed in ultraviolet light, allowing its red glow to dominate.

She, however, says that this happening is not exclusively related to the Hope Diamond.

Magana says that her team had also studied the phosphorescence of 66 other rare natural blue diamonds, including the world's second-largest Blue Heart blue diamond, along with the Hope Diamond.

She says that her research revealed that all natural blue diamonds phosphoresce with red or blue-green light in various ways.

"It's really not that rare," Discovery News quoted her as telling of the Hope Diamond's glow.

Magana has also found that the Hope Diamond not the best at the glow-in-the-dark trick. She says that several other blue diamonds glow red for a much longer period, 28 seconds in one case as compared to the Hope Diamond's 8.2 second glow.

She says that the unique mix of colours given off by different individual diamonds, coupled with each diamond's individual rate of fading, provides a new way to fingerprint any natural blue diamond.

This will help settle all questions about whether certain smaller stones were really cut from larger stones, such stones should share the same phosphorescent signature.