One of the more frequent terms you will hear when shopping for a diamond or gemstone is fluorescence. Fluorescence is usually defined as the emission of visible light from a mineral or gemstone when it is stimulated by radiation or shorter light wavelengths.
For instance, some gemstones will state fluorescence as its selling point. Usually the diamond or gemstone will undergo a burst of short wave light, x-rays or long wave light. Sometimes, fluorescence can be seen from shining normal daylight onto the stone or using high powered lamps.
Fluorescence is sometimes used to determine the quality of the stone, specifically traits that hint at the color. For instance, if a diamond undergoes a UV light and it fluoresces blue, this might be due to the fact that the diamond has a yellow hue in it, usually lowering the value of the stone.
Another method to test the fluorescence of an object is with a crossed filter. Usually very intense light is filtered through a special solution and then onto a gemstone. After after using this crossed filter, you can determine special qualities about a specific gemstone.
It should be noted that each gemstone fluoresces differently and no two stones fluoresce exactly the same way. While fluorescence might be stated, if you are shopping for a diamond or gemstone, it is always better to determine the value of the stone via traditional methods, for diamonds, this usually is the 4 C’s (carat, color, clarity and cut).