This emission, unlike phosphorescence, ceases as soon as the source of excitation is removed, and so the glow disappears. The light emitted is generally of a lower frequency than the radiation absorbed, which is generally ultraviolet light. Picture yourself proposing marriage in a romantic, candle-lit setting and noticing that your precious diamond engagement ring appears to be glowing in the dark. Medium to strong blue fluorescence in a diamond of D-H color may cause a foggy or milky quality in daylight with high UV lighting conditions. The lion's share of the diamonds I sell have a none to slight blue fluorescence.
Blue fluorescence can contribute to the enhancement of the natural beauty of some diamonds.
You may have heard of this effect as in ' premier ' diamonds. Nowadays some of my clients still ask for blue-white. I do recommend viewing a prospective diamond under uv light. Most jewelers will have a diamondlight with its own uv light source. If the diamond picks up a light neon blue hue under the uv light, it most probably has a slight fluorescence that may have little positive effect on the diamond's color grade or appearance.