An interesting property of some diamonds is that they can glow in the dark. When illuminated by ultraviolet light, certain diamonds can absorb the high-energy radiation and re-emit it as visible light. These diamonds are called fluorescent. Some can even continue glowing after the ultraviolet source is turned off. These diamonds are phosphorescent.

This 2.15-carat, cushion-cut diamond fluoresces in daylight but not in incandescent light, such as that given off by a light bulb. It is a color-change diamond, going from intense, greenish yellow in fluorescent light or daylight to yellowish brown in incandescent light. This Brazilian diamond has a historic pedigree, having been given by Pedro II de Alcantara (1825-91), emperor of Brazil, to his niece. Dom Pedro II, a descendant of the Hapsburg family and the Braganza royal family that ruled Portugal, ascended to the throne of Brazil in 1831 and ruled until 1889. He was a scientist in his own right and was greatly interested in diamonds, mineral specimens, and geology.