Diamond fluorescence is the ability of a diamond to emit light and change color when subjected to ultraviolet rays. For example, if you go to a night club and there happens to be UV light, your diamond may start glowing blue.
It is worth noting that not all diamonds fluoresce, and those that can glow differ in the intensity of the light they emit. Around one third of all diamonds are estimated to exhibit some kind of fluorescence.
The cause of diamond fluorescence is hidden within the stone. Diamonds contain different chemical elements, which, depending on their concentration, can glow in the dark.
Diamonds can fluoresce in many different colors, such as yellow, red and green, but the most widespread color is blue. Stones with non-blue fluorescence are extremely rare.
How Fluorescence Affects Diamond Quality
Whether the diamond is fluorescent and what color it glows will be usually listed on the stone’s grading report. The effect of fluorescence on the quality of a diamond, however, is a controversial topic.
The G.I.A. (Gemological Institute of America) has conducted a study on fluorescence and concluded that whether a diamond is fluorescent has no effect on how the average observer perceives the stone’s quality. It is also worth noting that the experts participating in the study could not agree on whether fluorescence has a significant effect on the appearance of a diamond.
There are jewelers who claim that in their experience, diamonds that exhibit strong fluorescence also tend to appear foggier.
The bottom line: You need to decide for yourself whether a particular diamond looks good to you, regardless of fluorescence. If you think the stone looks a bit misty, then go with another one. Don’t let fluorescence alone influence your decision without looking at the diamond as a whole.
Fluorescence and Diamond Prices
Because strongly fluorescent diamonds are considered by some people to be negatively affected by this characteristic, these stones can command lower prices compared to similarly graded, non-fluorescent diamonds. So, if you see a fluorescent diamond, check if it is a bargain – if you like its color, clarity and cut, you might save some money.
Some people find that for diamonds of lower color grades, i.e. stones that exhibit yellowish tints, blue fluorescence can actually improve the color appearance by masking the yellow color. Again, only you can decide whether this is true for any particular diamond.
Diamonds with yellow fluorescence are usually priced lower because it is thought that the yellow hues diminish the quality of the stone’s color.
After a fluorescent diamond is no longer exposed to UV light, it may continue to glow for a while. This property is rare and is called phosphorescence.
Considering Fluorescence When Buying Diamonds
When you are shopping for diamonds, ask to see the stone under both UV and normal lighting conditions. You should be aware of how the diamond looks in different settings before deciding.
Don’t forget to look at the stone when it is exposed to daylight. Remember that sunlight contains UV rays, which will bring out your stone’s fluorescent color when it is sunny.
Diamonds exhibiting yellow fluorescence will look yellow whenever UV rays are present, including in daylight. Keep this in mind if you don’t want anything to do with yellow when it comes to diamonds.
If a diamond is fluorescent, compare it with a non-fluorescent stone of similar quality in order to judge whether you can see any difference in color or clarity.
Synthetic diamonds don’t fluoresce, so if a stone is fluorescent, it is most certainly a real diamond; however, keep in mind that about two thirds of real diamonds don’t exhibit fluorescence.For more information on diamonds: Read our Diamond Cut Quality Guide.
Important: We recommend that you only buy diamonds that you have seen and examined in detail. Each diamond is unique, and a mere description of color, cut and clarity is not sufficient, as even stones of the same grades might look different.