Fluorescence - What You Need To Know


what is fluorescence?

Fluorescence is the visible light some diamonds emit when they are exposed to invisible ultraviolet (UV) rays. On a GIA diamond grading report, fluorescence refers to the strength, or intensity, of the diamond’s reaction to long-wave UV, which is an essential component of daylight. The light emitted lasts if the diamond is exposed to the ultraviolet source.  

Fluorescence is not graded like the four C's, but instead if a diamond does exhibit fluorescence, then its strength is measured and this will go on the diamond report. There are five strength grades: none; faint; medium; strong and very strong.

how does fluorescence impact on a diamond?

Only 25% - 35% of diamonds exhibit some degree of fluorescence, so it doesn't affect most diamonds and fluorescence affects different diamonds...well, differently.

For the rare white or colourless diamonds graded from D to H, fluorescence can emit a bluish tinge. Some also believe that a strong fluorescence can make a diamond appear hazy or oily in appearance. This means that these diamonds are frequently less expensive than ones which exhibit no fluorescence at all.

In diamonds at the other end of the colour spectrum; so diamonds graded from around an I to an M - the diamonds that emit a slightly yellowish tinge - fluorescence can sometimes be regarded as a good thing, as the blueish tinge can make the diamond appear whiter than it actually is.

is it important? Should you care?

The GIA (Gemmological Institute of America) conducted a study on fluorescence and concluded that blue fluorescence has a negligible effect on the appearance. In short, most people can not tell the difference between a diamond with fluorescence and one without.

To find out more, go to the GIA website here.