Flourescence

[thamvo]

What is Flourescence in a Diamond? Is a diamond with a Faint Flourescence bad? How about Medium Flourescence?

 

[DiamondExpert]

Faint or medium BLUE fluorescence will not affect the way the diamond looks.

Here is some stuff I wrote earlier for my web site - Fluorescence, produced by ultraviolet light from the sun, by black lighting or other long-wavelength UV source, occurs in an estimated 35% of gem grade diamonds, and >90% is blue. (Virtually all diamonds fluoresce when exposed to X-rays, and this forms the basis for their identification and collection at mining sites.)

The UV light excites electrons in the diamond crystal, which then release this absorbed energy in the form of visible light, producing a blue, or sometimes other color, of faint to very strong intensity. Once the light source is removed however, the fluorescence is no longer observed. If, in rare situations, light emission continues for a period after the exciting light has been turned off, the phenomenon is called phosphorescence.

Blue fluorescence, if strong or very strong, may alter the perceived color of a diamond in a negative or positive way. For example, stones in the colorless/near colorless ranges (D-F) may appear milky or oily, detracting from their appearance. On the other hand, diamonds in the lower, more yellow color ranges (G-I and lower) may appear to have less yellow color due to the fluorescence, adding positively to their appearance. Thus, the trade will sometimes slightly discount prices of diamonds in the former category, while sometimes adding a very slight premium to those in the latter. (Don't look for this to be a factor in Ideal or Super-Ideal cut diamonds.)

The presence and color (most frequently blue, but can be any color) of fluorescence and its intensity (none/inert, negligible, faint, medium, strong, very strong) are indicated on all GIA and AGS grading reports. However, these terms are considered by GIA to be only descriptive, and are not grading terms. (For an in depth study of blue fluorescence in diamonds, see: Gems and Gemology, Vol. 33, Winter, 1997, pp. 244-259.)

When shopping for a diamond, check to see if it has fluorescence. If it does make sure that it is BLUE and not some other color. The last thing you want in a colorless diamond is a potentially interfering fluorescing background color such as yellow, green or orange, which might greatly detract from the stone’s appearance. If the diamond has blue fluorescence, it probably won’t be a factor in the stone’s appearance UNLESS the intensity is strong or greater, and even then only infrequently is it a problem. Nevertheless, make sure you verify that there is no effect of fluorescence under all conditions of lighting – from bright sunlight to all types of artificial lighting.