Diamond Fluorescence

An estimated 1/3 of diamonds in the market are fluorescent when seen under the ultra violet (UV) light (or ultrasound). The effect is like white clothes in a nightclub or fluorescent minerals in the museums of natural history. Fluor ranges from faint to very strong. Some stones may also continue to glow for a while when they UV light is switched off.

The most common fluorescent color is blue, the complimentary color to yellow. As for yellow, it is the most common hue in diamonds. An important feature of blue fluorescence is that it changes the color of yellowish diamonds making them white or colorless.

You can also encounter diamonds with yellow or orange fluoro. Such diamonds, seen under the UV light, will have a lower color. Therefore, they should be only bought if they have the same hue as the fluorescence. In this case, fluoro will make the color of the diamond more intense.

The GIA poll discovered that fluorescence diamonds were in high demand than simple ones both in the lower and in the higher (D, E, F) colors, with the letter often discounted by the trade. Many years ago, colorless fluoro diamonds were considered most valuable. They were called “blue-white”. However, when sales people began to apply this name to any fluorescent diamond the US trade practices law forbade its usage.

The most obvious reason for fluorescent diamonds discounting is plain ignorance of jewelry sales people who cannot “interpret” such phenomenon as fluoro to the buyers, confused by any unclear comments written on a report.

The GIA Gem Trade Lab grading lights emit a small amount of UV light, so flouro diamonds can be assigned a better color grade. On the one hand, it is a good reason for discounting fluorescent diamond. On the other hand, UV light can be found in viewing environment, therefore color should be graded in realistic lighting.

There are diamonds, which look oily or cloudy due to extremely strong fluorescent. Though they are not regarded as good diamonds, such stones are very rare according to GIA research. There are little opportunities to find enough cloudy stones from more than 26 thousand samples.