This article explores diamond fluorescence, explaining how it affects the appearance and value of colorless and colored diamonds. It details the impact of different fluorescence intensities, including non-blue fluorescences like yellow and green. The article also covers how fluorescence varies under different lighting conditions and its market implications.
Table of Contents
1. What is Diamond Fluorescence?
Fluorescence in diamonds refers to the visible light emitted when a diamond is exposed to ultraviolet (UV) rays, such as those found in sunlight or under a UV lamp. This phenomenon is caused by trace elements within the diamond’s crystal structure, most commonly boron. When exposed to UV light, these elements can cause the diamond to emit a visible light, usually blue, but it can also appear in other colors such as yellow, green, orange, red, or even white.
Fluorescence Intensity: Fluorescence is graded by gemological laboratories on different scales. The most common scale used by labs like the GIA (Gemological Institute of America) and IGI (International Gemological Institute) includes grades such as None, Faint, Medium, Strong, and Very Strong. Some labs, like HRD Antwerp, may use slightly different terminology but follow similar grading principles, sometimes referring to "Slight" instead of "Faint."
The image above is from the GIA's educational materials
2. Effects of Different Fluorescence Colors in Diamonds
Fluorescence in diamonds is most commonly blue, but some diamonds exhibit fluorescence in other colors such as yellow, green, orange, red, and even white. Each type of fluorescence interacts differently with the diamond’s inherent color, and its impact can vary:
Blue Fluorescence: Blue fluorescence is the most prevalent and can either enhance or detract from a diamond’s appearance, depending on its color grade. In lower color grades, it can make the diamond appear whiter, while in higher color grades, strong blue fluorescence might cause a milky or hazy effect under UV light.
Yellow Fluorescence: Yellow fluorescence can accentuate any yellow tint in near-colorless diamonds, making them appear more yellow under UV light. In fancy yellow diamonds, however, this fluorescence can enhance the yellow hue, making the diamond appear more vibrant.
Green Fluorescence: Green fluorescence is rare and can impart a unique greenish glow under UV light. In green diamonds, this can enhance the stone’s color, while in white diamonds, it might introduce an undesired green tint.
Orange Fluorescence: Orange fluorescence, while uncommon, can deepen the color of orange or brown diamonds. In white diamonds, it might give an orange tint under certain lighting, which could be less desirable.
Red Fluorescence: Red fluorescence is extremely rare and can make red or pink diamonds appear more intense under UV light. This added intensity can increase the stone’s appeal and value.
White Fluorescence: White fluorescence can create a chalky or milky appearance under UV light. In high-color diamonds, this is often seen as undesirable as it can reduce the diamond’s brilliance and clarity.
3. Fluorescence in Different Lighting Conditions
Fluorescence affects how a diamond looks under different types of light:
Incandescent Light: Fluorescence is typically not visible under incandescent lighting, so the diamond will look like a non-fluorescent diamond in these conditions.
Sunlight: Natural sunlight contains UV rays, which can cause diamonds with strong fluorescence to glow faintly blue or another color, depending on the fluorescence type. This effect can enhance or detract from the diamond’s appearance, depending on its inherent color and the viewer’s preference.
UV Light (Nightclub or Black Light): In environments with UV light, such as nightclubs, diamonds with strong fluorescence can glow vividly. This can be a striking effect, but it can also make the diamond appear different than it does in natural or indoor lighting.
4. When Fluorescence is Beneficial or Detrimental
Fluorescence can be either an asset or a drawback, depending on the context:
Beneficial: Fluorescence is often beneficial in diamonds with lower color grades, where it can enhance the diamond’s appearance. Additionally, some buyers are specifically drawn to the unique glow that fluorescence can give a diamond under UV light, making these stones particularly appealing for certain settings, such as evening wear.
Detrimental: Conversely, in high-color diamonds, especially those intended for use in daylight or bright lighting, strong fluorescence can be seen as a flaw. The hazy effect under sunlight or UV light can detract from the diamond’s perceived purity and brilliance.
5. Fluorescence Impact on Colorless Diamonds
In colorless diamonds, fluorescence can have varying effects based on the diamond’s color grade and the intensity of the fluorescence. The most common fluorescence color in white diamonds is blue, which can enhance or detract from the diamond’s appearance.
Impact on Appearance: In high color grades (D-F), strong fluorescence can sometimes cause the diamond to appear milky or hazy under sunlight or UV light. However, in lower color grades (G-J), blue fluorescence can actually enhance the diamond’s appearance by counteracting any yellowish tint, making the diamond appear whiter.
Lighting Conditions: Under incandescent lighting (common indoor lighting), fluorescence is generally not visible, so the diamond will appear as it does without UV light. Under sunlight or in environments with UV light (such as nightclubs), fluorescence becomes more noticeable, potentially altering the diamond’s appearance.
6. How to Read the Fluorescence Impact Tables
In the tables provided, we have made some simplifications to ensure clarity and ease of understanding:
Simplified Fluorescence Intensity Categories: The levels of fluorescence intensity have been condensed into three main categories: Faint, Medium, and Strong. We have omitted the categories of None and Very Strong to streamline the presentation.
GIA and IGI Grading Equivalence: In the tables, GIA’s “Faint” fluorescence is equivalent to “Slight” fluorescence as graded by the IGI (International Gemological Institute). This is important to note when comparing diamonds graded by different institutions.
Simplified Color Characteristics: The characteristics of color—specifically hue, saturation, and tone—have been simplified into four categories: Light, Intense, Vivid, and Deep. These categories are based on human perception of color strength or richness, rather than detailed technical measurements, to provide a more accessible understanding of how fluorescence impacts diamond color.
Here’s a detailed table showing how fluorescence impacts different color grades in colorless diamonds:
Table 1: Fluorescence Impact on Colorless Diamonds
| Fluorescence Intensity | D-F (Colorless) | G-J (Near Colorless) | K-M (Faint) | N-Z (Very Light) |
|---|---|---|---|---|
| Blue – Faint | Good | Good | Bad | Neutral |
| Blue – Medium | Good | Good | Bad | Bad |
| Blue – Strong | Bad | Bad | Bad | Bad |
| Yellow – Faint | Bad | Bad | Bad | Good |
| Yellow – Medium | Bad | Bad | Bad | Good |
| Yellow – Strong | Bad | Bad | Bad | Good |
| Green – Faint | Neutral | Neutral | Bad | Neutral |
| Green – Medium | Bad | Bad | Bad | Bad |
| Green – Strong | Bad | Bad | Bad | Bad |
| Orange – Faint | Neutral | Neutral | Bad | Neutral |
| Orange – Medium | Bad | Bad | Bad | Bad |
| Orange – Strong | Bad | Bad | Bad | Bad |
| Red – Faint | Neutral | Bad | Bad | Neutral |
| Red – Medium | Bad | Bad | Bad | Bad |
| Red – Strong | Bad | Bad | Bad | Bad |
| White – Faint | Bad | Bad | Bad | Bad |
| White – Medium | Bad | Bad | Bad | Bad |
| White – Strong | Bad | Bad | Bad | Bad |
7. Fluorescence in Colored Diamonds
In colored diamonds, fluorescence can have unique effects. For instance, yellow diamonds with blue fluorescence may appear greenish under UV light due to the interaction between their inherent color and the fluorescence. Pink or blue diamonds with fluorescence might exhibit an intensified or altered hue when exposed to UV light.
The image above is from the GIA's educational materials
Impact on Rarity and Value: In some cases, fluorescence can add a layer of intrigue and uniqueness to colored diamonds, potentially making them more desirable to certain buyers. However, strong fluorescence can also make the color appear uneven or less consistent, which may reduce the diamond’s appeal.
8. Fluorescence Impact on Fancy Colored Diamonds
Here are the tables that detail how fluorescence impacts yellow, pink, green, and blue diamonds across different intensity levels.
Table 2: Fluorescence Impact on Yellow Diamonds
| Fluorescence Intensity | Fancy Light Yellow | Fancy Intense Yellow | Fancy Vivid Yellow | Fancy Deep Yellow |
|---|---|---|---|---|
| Blue – Faint | Good | Good | Good | Good |
| Blue – Medium | Good | Good | Good | Good |
| Blue – Strong | Bad | Bad | Bad | Bad |
| Yellow – Faint | Good | Good | Good | Good |
| Yellow – Medium | Good | Good | Good | Good |
| Yellow – Strong | Good | Good | Good | Good |
| Green – Faint | Neutral | Neutral | Neutral | Neutral |
| Green – Medium | Bad | Bad | Bad | Bad |
| Green – Strong | Bad | Bad | Bad | Bad |
| Orange – Faint | Neutral | Neutral | Neutral | Neutral |
| Orange – Medium | Bad | Bad | Bad | Bad |
| Orange – Strong | Bad | Bad | Bad | Bad |
| Red – Faint | Neutral | Neutral | Neutral | Neutral |
| Red – Medium | Bad | Bad | Bad | Bad |
| Red – Strong | Bad | Bad | Bad | Bad |
| White – Faint | Bad | Bad | Bad | Bad |
| White – Medium | Bad | Bad | Bad | Bad |
| White – Strong | Bad | Bad | Bad | Bad |
The colors of the diamonds shown are (from left to right): Fancy Deep Brownish Yellow, Fancy Vivid Yellow Orange, Fancy Vivid Yellow Orange, Fancy Deep Grayish Yellowish Green/Chameleon, Fancy Dark Gray Yellowish Green/Chameleon, Fancy Intense Yellow, Fancy Pink, Fancy Greenish Yellow, Fancy Intense Green Yellow, Fancy Intense Green Yellow.
Source: Benji Margolese, Leibish
Table 3: Fluorescence Impact on Pink Diamonds
| Fluorescence Intensity | Fancy Light Pink | Fancy Intense Pink | Fancy Vivid Pink | Fancy Deep Pink |
|---|---|---|---|---|
| Blue – Faint | Neutral | Neutral | Neutral | Neutral |
| Blue – Medium | Neutral | Neutral | Neutral | Neutral |
| Blue – Strong | Bad | Bad | Bad | Bad |
| Yellow – Faint | Neutral | Neutral | Neutral | Neutral |
| Yellow – Medium | Bad | Bad | Bad | Bad |
| Yellow – Strong | Bad | Bad | Bad | Bad |
| Green – Faint | Neutral | Neutral | Neutral | Neutral |
| Green – Medium | Bad | Bad | Bad | Bad |
| Green – Strong | Bad | Bad | Bad | Bad |
| Orange – Faint | Good | Good | Good | Good |
| Orange – Medium | Good | Good | Good | Good |
| Orange – Strong | Good | Good | Good | Good |
| Red – Faint | Good | Good | Good | Good |
| Red – Medium | Good | Good | Good | Good |
| Red – Strong | Good | Good | Good | Good |
| White – Faint | Bad | Bad | Bad | Bad |
| White – Medium | Bad | Bad | Bad | Bad |
| White – Strong | Bad | Bad | Bad | Bad |
Table 4: Fluorescence Impact on Blue Diamonds
| Fluorescence Intensity | Fancy Light Blue | Fancy Intense Blue | Fancy Vivid Blue | Fancy Deep Blue |
|---|---|---|---|---|
| Blue – Faint | Good | Good | Good | Good |
| Blue – Medium | Good | Good | Good | Good |
| Blue – Strong | Bad | Bad | Bad | Bad |
| Yellow – Faint | Neutral | Neutral | Neutral | Neutral |
| Yellow – Medium | Bad | Bad | Bad | Bad |
| Yellow – Strong | Bad | Bad | Bad | Bad |
| Green – Faint | Neutral | Neutral | Neutral | Neutral |
| Green – Medium | Bad | Bad | Bad | Bad |
| Green – Strong | Bad | Bad | Bad | Bad |
| Orange – Faint | Good | Good | Good | Good |
| Orange – Medium | Good | Good | Good | Good |
| Orange – Strong | Good | Good | Good | Good |
| Red – Faint | Neutral | Neutral | Neutral | Neutral |
| Red – Medium | Bad | Bad | Bad | Bad |
| Red – Strong | Bad | Bad | Bad | Bad |
| White – Faint | Bad | Bad | Bad | Bad |
| White – Medium | Bad | Bad | Bad | Bad |
| White – Strong | Bad | Bad | Bad | Bad |
Fun Fact: The famous blue Hope Diamond actually fluoresces cherry red!
Table 5: Fluorescence Impact on Green Diamonds
| Fluorescence Intensity | Fancy Light Green | Fancy Intense Green | Fancy Vivid Green | Fancy Deep Green |
|---|---|---|---|---|
| Blue – Faint | Neutral | Neutral | Neutral | Neutral |
| Blue – Medium | Bad | Bad | Bad | Bad |
| Blue – Strong | Bad | Bad | Bad | Bad |
| Yellow – Faint | Neutral | Neutral | Neutral | Neutral |
| Yellow – Medium | Bad | Bad | Bad | Bad |
| Yellow – Strong | Bad | Bad | Bad | Bad |
| Green – Faint | Good | Good | Good | Good |
| Green – Medium | Good | Good | Good | Good |
| Green – Strong | Good | Good | Good | Good |
| Orange – Faint | Neutral | Neutral | Neutral | Neutral |
| Orange – Medium | Bad | Bad | Bad | Bad |
| Orange – Strong | Bad | Bad | Bad | Bad |
| Red – Faint | Neutral | Neutral | Neutral | Neutral |
| Red – Medium | Bad | Bad | Bad | Bad |
| Red – Strong | Bad | Bad | Bad | Bad |
| White – Faint | Bad | Bad | Bad | Bad |
| White – Medium | Bad | Bad | Bad | Bad |
| White – Strong | Bad | Bad | Bad | Bad |
9. How Fluorescence Affects Diamond Pricing
Fluorescence can significantly influence the price of a diamond, with the impact varying based on the intensity of the fluorescence and the diamond’s color grade. Understanding these effects can help buyers make informed decisions. Below is a summary of how different levels of fluorescence impact diamond pricing:
Table 6: Fluorescence Impact on Pricing
| Fluorescence | Things to Consider |
|---|---|
| None | Excellent – No discount applied. |
| Faint | – D-E Color: Good, with a 3-6% discount on the price. |
| – F-G Color: Very Good, with a 2-3% discount on the price. | |
| – H and Above: Excellent, with a 0-2% discount on the price. | |
| Medium | – D-E Color: Good, with a 6-8% discount on the price. |
| – F-G Color: Very Good, with a 2-5% discount on the price. | |
| – H and Above: Excellent, with a 0-2% discount on the price. | |
| Strong | – D-E Color: Fair to Good, with a 12-18% discount on the price. |
| – F-G Color: Good to Very Good, with an 8-12% discount on the price. | |
| – H and Above: Very Good to Excellent, with a 4-10% discount on the price. | |
| Very Strong | – D-E Color: Poor to Good, with a 15-20% discount on the price. |
| – F-G Color: Fair to Very Good, with a 10-15% discount on the price. | |
| – H and Above: Very Good to Excellent, with a 5-11% discount on the price. |
Considerations for Buyers
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High-Color Diamonds (D-F Grades): In high-color diamonds, strong and very strong fluorescence can significantly lower the price due to potential visual effects like haziness or a milky appearance under certain lighting conditions.
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Mid-Color Diamonds (G-J Grades): For diamonds in this range, faint to medium fluorescence may be more acceptable or even desirable, as it can enhance the diamond’s appearance without major price penalties.
-
Lower-Color Diamonds (K and Above): Diamonds in this category tend to be less affected by fluorescence in terms of price. In some cases, fluorescence can improve the perceived color, especially in diamonds with warmer tones.
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Market Preferences: Different markets have varying preferences regarding fluorescence. For instance, some buyers may seek out diamonds with no fluorescence, especially in the U.S., where a premium is often placed on non-fluorescent stones.
By understanding how fluorescence impacts pricing, buyers can better navigate the market and select diamonds that align with their aesthetic preferences and budget.
10. Irradiation and Fluorescence in Diamonds
Irradiation is a treatment process where diamonds are exposed to high-energy particles such as electrons, neutrons, or gamma rays. This treatment alters the diamond’s atomic structure, often changing its color and potentially inducing fluorescence.
- How Irradiation Causes Fluorescence: Irradiation affects the crystal structure of a diamond by creating vacancies or defects in the carbon lattice. These structural changes can interact with trace elements already present in the diamond, such as nitrogen or boron, leading to fluorescence when the diamond is exposed to ultraviolet (UV) light. The fluorescence induced by irradiation can vary in color, including blue, green, yellow, or even pink, depending on the type of treatment and the diamond’s composition.
- Implications of Irradiation-Induced Fluorescence:
- Color Enhancement and Fluorescence: Irradiation is often used to enhance or change the color of a diamond, such as turning a colorless diamond into a vivid green or blue. These treated diamonds may show fluorescence as a side effect, which can either enhance their visual appeal or make them appear artificial under certain lighting conditions.
- Market Perception and Value: Diamonds that have been treated with irradiation are generally less valuable than untreated diamonds of similar appearance. The presence of fluorescence, especially if it is intense or in a non-traditional color, can further influence the diamond’s market value. Some buyers may find the fluorescence appealing, while others may see it as a sign of treatment and prefer untreated stones.
- Identification and Disclosure: It is crucial for irradiated diamonds to be properly identified and disclosed when sold. Gemological laboratories like GIA, IGI, and HRD can detect irradiation treatments and report them in the diamond’s certification. This includes noting any induced fluorescence as a result of the treatment.
11. Additional Considerations for Buyers
When considering a diamond with fluorescence, it’s important to view it under multiple lighting conditions. This will help you understand how the diamond’s appearance may change depending on where it will be worn.
Personal Preference: Ultimately, the choice of whether or not to buy a diamond with fluorescence depends on personal preference. Some people love the unique glow it provides under UV light, while others may prefer the consistent appearance of a non-fluorescent diamond.
Certification and Grading: Be sure to check the diamond’s grading report from a reputable laboratory, such as the GIA, IGI, or HRD, which will note the presence and intensity of fluorescence. Understanding this characteristic will help you make an informed decision.
Conclusion
Diamond fluorescence is a characteristic that adds another layer of complexity to choosing the perfect stone. While it can enhance a diamond’s appearance in some cases, it can also detract from it in others. Understanding how fluorescence interacts with different types of diamonds and lighting conditions, as well as recognizing the effects of treatments like irradiation, will empower you to make a more informed decision that aligns with your aesthetic preferences and lifestyle.
Whether considering a colorless diamond or a fancy colored one, evaluating fluorescence alongside other factors such as cut, clarity, and color is essential to selecting a diamond that meets your expectations both in beauty and value.