The famed Hope Diamond glows a mysterious red when exposed to ultraviolet light, a finding that scientists say can help them "fingerprint" blue diamonds and tell the real ones from the artificial. The phosphorescence comes from boron in the gem, the same element that makes it appear blue in normal light, explained Jeffrey Port, curator of the National Gem Collection at the Smithsonian. But while all blue diamonds glow in ultraviolet light, most glow blue. The Hope glows red, indicating a different mix of boron and nitrogen...

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