Diamond Fluorescence: Everything You Need To Know

Diamond Fluorescence Described

When grading diamond color the stone will also be checked for fluorescence. About 30% of diamonds have some amount of fluorescence, caused by chemicals in the earth where it formed. Fluorescence can be excited by ultraviolet light or x-rays, and re-emit visible light. In most cases fluorescence is blue, but colors such as yellow, white, orange and red are possible. The strength and color of fluorescence will always be noted on grading reports issued by top-tier laboratories.

How is fluorescence graded?

Short-wave and long-wave ultraviolet light are used to test diamonds for fluorescence. When present, the strength and color of fluorescence will be noted on the grading report.

Fluorescence Chart

The scale above is used by GIA and most other laboratories. The AGS examines and reports fluorescence differently:

AGS uses the term “negligible” for diamonds with faint or lower fluorescence: First, because the presence of fluorescence at these low levels has negligible impact. Second, because AGS prefers not to state none when stronger levels of UV might make some amount of fluorescence discernible.

AGS grades fluorescence by observing the diamond in the face-up position, since fluorescence can sometimes be directional, and they wish to grade its influence the same way the diamond will normally be viewed.

In keeping with the above, GIA qualifies their grade of “none” as follows: “A fluorescence description of ‘none’ represents a range of fluorescence from indiscernible to very faint. Used for identification purposes.”

Will I see fluorescence?

MAYBE.

It depends on the strength and color of fluorescence in the diamond, the brightness of the environment and how much ultraviolet light is present.

Medium, Strong and Very Strong Blue Fluorescence can usually be seen in a dark room when UV light (such as black lights in a dance club) is present. Medium Blue typically shows itself as a soft blue glow, while Very Strong Blue appears to be lit from within. If the UV source is strong enough, the faint glow of Faint Blue Fluorescence can also be detected.

The influence of Strong and Very Strong Blue Fluorescence can frequently be detected in sunlight, which has a natural ultraviolet component. In general terms, a hint of blue can be seen in casual appearance as well as its underlying optical performance.

Very Strong Fluorescence Example

The two photos below show the same 1.34ct diamond. The photo on the left shows what the stone looks like under normal lighting conditions. The photo on the right shows the same stone mounted in a ring, with a strong UV light directed at it, causing the very strong blue fluorescence present to become excited.

Does Fluorescence Impact Value?

YES.

Fluorescent diamonds are traded at a discount, usually in proportion to the strength of fluorescence. D, E and F colored diamonds with fluorescence are discounted more severely than near-colorless and lower diamonds. Whatever the case, you will find that diamonds with medium and higher fluorescence nearly always trade at a discount.

The amount of devaluation is not always inconsistent. For most diamonds, it lands somewhere between 10-25%. For D, E and F colors it can leap to 35%. This chaos makes future value certainty impossible. As a result, some diamond sellers do not make the same guarantees for diamonds with fluorescence that they do for diamonds with negligible or no fluorescence.

Long term value: Our vetted vendors include Whiteflash, Blue Nile and JamesAllen.com – all of whom inspect the diamonds they sell to protect you from any deleterious effects of fluorescence. They have experts ready to listen and help you determine which combo of the 4Cs is perfect for you – and nicely in budget. Call or chat now, and get help today.

Intermediate Diamond Fluorescence

Fluorescence is feared and celebrated for different reasons. Long ago, when diamonds largely came from one source in Africa, a series of “overblue” fluorescent diamonds created negative perception about all diamond fluorescence. That reputation persists today, even though such overblue examples are exceedingly rare now. Alternately, those selling diamonds with fluorescence may enthusiastically point to “color improvement,” due to blue fluorescence – which is possible but not always present.