Diamond Fluorescence

Fluorescence negatively affects a diamond’s price, making it look lifeless. However, it does not have the same impact on all diamonds; in some cases, it might even be a positive factor. Here are some scenarios when fluorescence might work in your favor:

1. Price: Since fluorescence is perceived as a negative factor universally without being dealt with on a case-by-case basis, it presents an opportunity for a buyer to grab an exceptional diamond at a discounted price.
2. Positive effects: Blue fluorescence is frequently beneficial in diamonds with a yellow tint (H, I, J colors or lower grades). This is because blue compliments yellow and makes a diamond appear whiter than its color.
3. Level of intensity: Fortunately, the intensity with which a diamond emits fluorescence is not the same. While stronger vigor often leads to a higher negative impact, lower intensity ranges, i.e., faint or medium blue, usually do not drastically harm a diamond's brilliance.
4. It does not hurt all diamonds the same way: In some cases, fluorescence might make a diamond look overly dull or oily; in others, it might not impact the visual appearance. However, most diamonds with fluorescence get a discounted price because of the perception problem, even if it does not affect their beauty.

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Image Credit: GIA

Fluorescence Scale and Observations

Carefully review the chart below containing our summarized insights on diamond fluorescence. Please also check the subsequent chart on discounts you might get in a given fluorescence range and why color is a significant factor in determining them. 

The picture below shows how diamonds that emit different types of fluorescence look in regular settings. It is hard to distinguish between diamonds with no fluorescence and those that emit fluorescence while inspecting them with the naked eye. Observing this effect is harder under indoor lighting, though it may be easier to detect under sunlight.

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Key Critical Observations

• Fluorescence is an invisible glow that some diamonds emit under Ultraviolet (UV) rays. After evaluating hundreds of diamonds, we can confirm that many exceptional diamonds are unnecessarily avoided due to mild fluorescence.
• In a nutshell, in D-F color diamonds, no fluorescence is a must. In G color diamonds, none to faint fluorescence is good. In H-Z color diamonds, medium to strong blue fluorescence can be a helpful factor because it is a complementary color to yellow.
• Among the 4Cs, the key relationship of fluorescence is with color. To understand the effects of fluorescence, a buyer must know how it relates to the color of a diamond. It is generally not desirable in colorless white diamonds (D-F color range), though it can be a positive factor in H and lower color ranges.
• If you buy a diamond with fluorescence, make sure you have a solid return policy in case the fluorescence negatively affects the stone (making it look oily or hazy in front of the sun), which is the case in less than 10% of diamonds with fluorescence in them.
• To summarize, fluorescence in a diamond generally affects its price negatively. However, this is not often the case in the I-Z color range, especially for faint or medium blue fluorescence.

Estimated Discount by Percentage Breakdown

This diamond price discount breakdown by fluorescence type is our rough estimation based on color. The discount percentage will change depending on how big the stone is and how significantly its fluorescence influences it, especially if its effect is negative (making it look dull or hazy).

The estimated price discount above should not be viewed as absolute as it might change from diamond to diamond and the degree to which fluorescence affects brilliance positively or negatively. Generally speaking, you will get a higher discount on D-E color diamonds with fluorescence. In F/G colors, the discount may be lower in the faint range, but it can be higher in the medium-to-strong blue range. In H, I, and J color (even up to Z), you may not get any discounts because the fluorescence can positively influence the brilliance of the diamond. As mentioned earlier, blue is a complementary color to yellow and might make such stones look whiter than their actual color grade.

As confirmed in the Gemological Institute of America’s (GIA’s) study, we also guarantee that consumers will often not be able to detect the presence of fluorescence in a diamond. Furthermore, most diamonds with fluorescence can have as much brilliance as those without it. The milky, hazy, and oily appearance of a diamond can also be found in stones with no fluorescence.

The most important factor in a diamond is its appearance; if you are happy with its appearance, do not worry about fluorescence. Instead, enjoy the 4-15% discount you may get when you buy a diamond with fluorescence. We believe the discount should be up to 2% for faint fluorescence, up to 5% for medium blue, 12% for strong blue, and 18% for very strong blue.

Summary of GIA's Study

Of the diamonds submitted to GIA over the past decade, around 25% to 35% exhibited some fluorescence level. In under 10% of these diamonds, fluorescence affected the appearance of the diamond. However, this effect is not necessarily harmful and can sometimes complement a diamond’s brilliance. The visible color is blue in more than 95% of the diamonds exhibiting fluorescence. Since blue is a complementary color to yellow, tinted diamonds look more colorless.

None or No Fluorescence: After reviewing a random sample of 26,010 diamonds, GIA found that only 9,175 or 35% exhibited some level of fluorescence. In GIA's words: "None" means that any fluorescence shown is weaker than the reference stone's. The institute notes, "a report description of ‘none’ means that any fluorescence exhibited is weaker than that of the reference stone that marks the none/faint boundary.”

Faint Fluorescence: After reviewing a random sample of 26,010 diamonds, GIA found that only 9,175, or 35%, exhibited some level of fluorescence. Of the 9,175 diamonds, 3,465, or 38%, reported faint fluorescence. Please note that GIA considers faint fluorescence the lower end of blue fluorescence, e.g., faint blue, medium blue, strong blue, and very strong blue.

Medium to Very Strong Blue Fluorescence: After reviewing a random sample of 26,010 diamonds, GIA found that only 9,175, or 35%, exhibited some level of fluorescence. Of the 9,175 diamonds, 62% or 5,710 had blue fluorescence, ranging from medium to very strong blue. While 97% of these fluoresced blue in varying intensities, 3%, or 162 stones, fluoresced other colors, such as yellow, white, and orange.

Of the 11,901 diamonds in the D-to-F range evaluated in the study, 3,250 fluoresced.

Key Findings of the GIA Study

1. For average buyers (consumers), no systematic effect of fluorescence was observed.
2. Even experienced observers or graders did not agree on the effect of fluorescence on the stones they were given to evaluate.
3. Diamonds with strongly blue-colored fluorescence were perceived to have a higher grade than their actual color grade.
4. Most observers did not find any connection between fluorescence and diamond clarity.

Please watch the video by Petra Gems to learn important tips about diamond fluorescence and how it affects the price of a diamond.

Some of our key thoughts on diamonds with fluorescence:

• Fluorescence in most diamonds does not affect the overall appearance of the diamond. It can be a positive factor if it is near colorless or tinted.
• Blue fluorescence can help make near-colorless diamonds look colorless. We have seen H-colored diamonds with medium blue fluorescence that look colorless to the naked eye.
• Strong blue fluorescence is not necessarily bad. Many diamonds with strong blue fluorescence do not adversely affect their appearance. Once, we observed an M color diamond looking like a near-colorless diamond because of very strong blue fluorescence.
• Diamonds with very strong fluorescence, always blue, are not common.
• Fluorescence is your ally, not your adversary because it can reduce the price of a diamond by 4–10%. The cost of a diamond is not significantly affected if it has medium blue or faint fluorescence.
• In some cases, diamond fluorescence may affect the overall appearance of a diamond. Avoid diamonds with fluorescence that look hazy, oily, or cloudy. Fluorescence can make diamonds look foggy or cloudy in very few cases, so it is best to avoid them. Ask your diamond dealer about such a possibility before making the purchase.
• Inquire about the dealer's return policy and make sure you can return your diamond if you end up not liking the look because of its fluorescence or for any other reason.
• It is common for high-grade diamonds to have blue fluorescence, such as D or E color diamonds. It is also found in F-color diamonds.

Important facts about Fluorescence in a Diamond

Do all diamonds fluoresce? No! When GIA analyzed about 26,000 diamonds, only 25-35% of them exhibited some level of fluorescence.

Can fluorescence be seen with the naked eye or in any lighting? You might see fluorescence under very bright sunlight or in places with strong UV rays, such as a tanning bed. Once the source of UV rays is removed, you will not be able to see the fluorescence.

Can fluorescence be easily identified and detected? No, it is tough for trained gemologists to see it. Most gemologists use high-tech tools to figure out the degree of fluorescence in a diamond.

Why is fluorescence not a grading factor like the 4Cs? While GIA considers fluorescence an identifying characteristic in a diamond, we believe it is a significant price and quality factor. It can be helpful in certain diamonds but is generally a slight negative factor in colorless ones.

Is fluorescence only blue in diamonds? While blue is the dominant color in fluorescence, there are also yellow, orange, red, white, and green colors. However, the latter colors are usually less desirable and least preferred than blue.

How bad is strong blue fluorescence? We have explained this in detail in this article. It generally depends on the color grade and is not always a negative influence. You will have to look at it case by case and inspect the diamond in person. You might end up lucky and get an extra discount while also getting a diamond with strong blue fluorescence with no adverse effect.

Can diamond fluorescence make a diamond less durable? No, fluorescence does not influence the durability of a diamond; the latter’s structural integrity remains intact.

Fluorescence working to your advantage

1. You may get a 4% to 10% discount on your diamond purchase without compromising quality. In our opinion, the discount should be up to 2% for faint fluorescence, 5% for medium blue, 12% for strong blue, and 18% for very strong blue.
2. Medium blue fluorescence might enhance the color of your diamond if it is within the H-L range or higher.
3. Faint fluorescence will also help you save money on your diamond without losing its overall brilliance.
4. When buying a diamond with fluorescence, make sure you have the option of returning it to be on the safe side.

Range of Diamond Fluorescence in GIA grading reports:

None or no fluorescence, medium blue, strong blue, very strong blue, faint, yellow, and green. Blue is the most common form of fluorescence in diamonds.

Additional Background:

Most of you have noticed the term "Fluorescence" on GIA or AGS Diamond Grading Reports or Petra Gems blogs. Unfortunately, the concept of fluorescence is often misunderstood. According to GIA, it is ultraviolet (UV) light's effect on a diamond and delineates its strength against the long-wave UV light. It is an invisible glow that a diamond emits under UV rays. GIA scale uses five grades to identify fluorescence: None, Faint, Medium, Strong, and Very Strong. More than 95% of the time, the fluorescence color is blue, but diamonds can also fluoresce other colors, mainly yellow.

Given the invisible property, fluorescence will often have no impact on the aesthetics of a diamond. A typical diamond wearer will not see that effect if the grade of Faint, Medium Blue, and in some cases, Strong Blue fluorescence is chosen.

What are the misconceptions about Fluorescence?

Some websites discuss fluorescence as a negative factor for diamonds. The two most misunderstood concepts in fluorescence are color and strength. A diamond will look whiter if it fluoresces blue. Do not panic if the diamond fluoresces blue; it is recommended in the H to J color range. Most high color grades, such as D-E, will often have blue fluorescence.

As stated at the beginning of this blog, the fluorescence grade ranges from None to Very Strong. Diamonds with very strong fluorescence tend to have a milky look even under everyday lighting conditions. A diamond might rarely appear dirty or cloudy to a typical observer under very strong fluorescence. A good rule of thumb would be to double-check with your diamond dealer about the effect of fluorescence on the diamond you are considering purchasing. Avoid buying a diamond with intense fluorescence in terms of strength.

Frequently Asked Questions About Diamond Fluorescence

If I had the option to pick between no or faint/medium blue fluorescence, what would be the best choice for me?

Generally, no fluorescence is preferred. However, blue fluorescence is helpful and recommended in H, I, and lower color diamonds. If you can, avoid it in D-G color diamonds. Faint is also great for G color.

Why is fluorescence perceived negatively?

Because it is not a black and white topic such as carat weight or color, consumers have no clarity about how to go about fluorescence. Hence, they generally try to be on the safe side and assume the worst.

What about fluorescence in D-F color diamonds, and why should it be avoided in such a range?

In most cases, fluorescence in D to F color diamonds does not negatively impact the stone. In very few cases, it can make the diamond look bluish, so most people prefer to avoid it. However, some prefer the bluish hue of white diamonds, so that might be your preference.

Is strong blue fluorescence bad?

You could get fortunate with strong blue fluorescence. People assume it is a super negative factor and avoid it, but it is not bad in H and low-color diamonds. It can help them look much whiter than their color since blue complements yellow. But, in D- G color diamonds, it can be somewhat negative. Therefore, make sure you see the diamond in person to determine how the fluorescence affects it or have a solid return policy if you buy a D-G color diamond with strong or very strong blue fluorescence.