What is Diamond Fluorescence?

Posted on Monday, July 9th, 2012 at 11:10 am by Debbie Fox

Take Away:
You may be able to save money when purchasing a diamond with a color of H or below. Look for a faint to medium blue fluorescence so the diamond appears whiter, but be sure you see it in person under optimal lighting before you make your purchase. If buying a diamond with a color of G or above, look for no to faint blue fluorescence so your diamond doesn’t look hazy.

Diamond fluorescence is when diamonds emit a soft glow under UV light, much like a white shirt is bright under a “black” light. Sometimes diamond fluorescence can save you money or give you a better looking diamond. There are some important factors to consider when selecting a diamond.

Examples of Diamond Fluorescence

Diamond Fluorescence from none to very strong

Diamond fluorescence is a hotly debated topic in the diamond industry. But an in-depth study by the GIA (Gemological Institute of America) in 1997 suggested that fluorescence makes very little difference in the appearance of a diamond. More importantly, most consumers can not see a difference between diamonds that do and do not fluoresce (But there are certain fluorescent diamonds to avoid though--described later.). Here’s an excerpt from the GIA study:

"For the average observer, meant to represent the jewelry buying public, no systematic effects of fluorescence were detected. Even the experienced observers did not consistently agree on the effects of fluorescence from one stone to the next. "In general, the results revealed that strongly blue fluorescent diamonds were perceived to have a better color appearance when viewed table-up [ed: right-side up, as when placed in a setting] with no discernible trend table-down [ed: upside-down]. Most observers saw no relationship between fluorescence and transparency."

About one third of all gem quality diamonds fluoresce, and while they can fluoresce in many colors, almost all fluoresce blue. fluorescence is graded by GIA and AGS (American Gem Society) from inert, faint, negligible, medium, strong and very strong. The visible effects of diamond fluorescence grades of medium or below can only be detected by a trained gemologist under controlled lighting conditions. Diamonds with strong fluorescence often appear hazy in regular light, and can affect the beauty of your diamond. This is especially true of diamonds with a higher (better) color grade (approximately G or above). A diamond’s beauty in these color grade may even be affected by a medium fluorescence grade.

But fluorescence affects diamonds with a lower color very differently. For lower color diamonds (approximately H color and lower), fluorescence may make the diamond appear to have less of a yellow tint, making the diamond look better.

The diamond industry has slightly adjusted prices for fluorescence in diamonds but not fully. Diamond pricing appears to be influenced by gemological statistics and full credit is not given to the ultimate beauty seen by the average consumer. Therefore, there are opportunities if one choses carefully.

When shopping for a diamond, it is best to view fluorescence diamonds in person under correct lighting, as the appearance varies from diamond to diamond. For example, some diamonds with a medium or strong fluorescence in a higher color grade will be sold at a discount. But upon viewing, you may determine that a diamond is spectacular and unaffected by the fluorescence.