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Diamond Fluorescence - Separating Fact From Fiction
Consumers shopping for diamonds both at B&M's and with Internet vendors are receiving conflicting and erroneous information regarding the effects of blue diamond fluorescence on a diamond's visual appearance. The dispensed advice takes the following forms:
1. Blue Fluorescence (FL) is bad, stay away. 2. FL in lower color diamonds, e.g.; I-J-K is a positive in that it will make the diamond face up whiter but only if the FL is faint or Medium, not Strong. In higher colors (D-H) it is detrimental; stay away. 3. Strong FL is to be avoided at all costs. 4. FL diamonds need to be priced and sold at a discount relative to comparable carat weight, color/clarity-cut diamonds that are non-FL.
Above: Diamonds exposed to concentrated long-wave ultraviolet radiation of a UV lamp.
Much of today's consumer attitudes and behavior regarding FL can be traced back to the Diamond Industry's perception of FL. Briefly, some diamond merchant's would look for near-colorless to light yellow diamonds with strong blue diamond FL because they believed that such FL imparted a more colorless appearance under lighting with a high UV content.
In the late 70's during the diamond "bren" when prices skyrocketed daily (analogous to the Tulip craze of the early 1800's), some diamantaires observed that some gem diamonds with a very hazy appearance also fluoresced strong blue to UV radiation. These dealers started offering significantly lower prices for these "Milky D's (D color diamonds with very strong FL and reduced transparency) and very strong FL also termed "overblues". Gradually this perceived negative impact of FL spread downwards to encompass color grades as far as F. In addition, with the significant influx of Russian goods which contain Med to Strong FL into the market, this perceived negative effect of FL has been exacerbated.
Additional industry concerns about blue diamond FL took on the following perceived factors:
1. Non-FL diamonds were thought to be more pure than blue FL stones,
2. Non-FL diamonds in the D-F color range were thought to be rarer than FL counterparts, and
3. The hazy appearence in the "overblues" must also exist to some deleterious degree in weaker FL diamonds as well.
A 1993 South Korean TV expose aimed at consumers on FL further served to highlight these perceived negative aspects of FL.
Martin Rapaport, Editor of the industry trade letter, The Rapaport Report, took these notions of FL one step further by codifying these artificially trade induced price differentials into his Rap pricing sheet, thus further solidifying the notion that blue diamonds were worth less.
The fact is that FL is not a negative, on the contrary it can be and is a positive factor. Several of us in the trade have known and advocated position.
In 1997, GIA conducted an extensive study on the effects of blue diamond FL on visual perception. Consumers and tradespeople were both asked to evaluate the effects of FL on their visual perception and to note any meaningful distinctions between non-FL to FL blue diamonds of differing FL intensities.
The results of this GIA study were highly instructive and surprising. GIA found that non-trade observers could not make ANY meaningful distinctions between non-FL to the FL blue diamonds and that FL blue diamonds had no overall effect on the diamond's color or transparency!
Above: E and G color set of diamonds under UV light.
From left to right, E color set shows: Strong, Medium, Very Strong, Medium, Medium, None Fluorescence.
G Color set from left to right shows UV Fluorescence of: Faint, Very Strong, Medium, Medium, None, Strong.
For the experienced observers that encompassed tradespeople, the strength of FL had no significant effect on the color appearance of the diamonds when viewed table-down (typical of lab grading). In the table-up position (which is the way consumers view the diamonds at B&M's and diamond showrooms), diamonds that were described as strong FL or very strong FL were, on average, reported to have a better color appearance than less FL stones. Strong FL was reported to have little impact on perceived transparency of the diamonds.
Above: Target diamond is measured for Fluorescence between two reference diamonds. Intensity of fluorescence should be stronger than the reference diamond on the left but weaker than the reference stone on the right.
The link to this GIA study is here:
http://www.gia.edu/pdfs/W97_fluoresce.pdf
This is a very important study and should be required reading for both consumers and all diamond and jewelry professionals. There are no grounds to consider blue diamonds in a negative light and therefore no basis for price differentiation relative to non blue diamonds.
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Comments
I have a diamond GIA certified, that looks blue in some light, but it is graded G color VV2 clarity and no florensce. Is this possible?
Posted by: Mary Kelsey on January 7, 2007 9:45 AM
The Blue diamonds were a hit in the early 1900's. Now we dicovered that they pose a haziness compared to a clear diamond.
What is the $ downgrade if you find that you have a one carot+ now? Bought yesterday. If the age of the diamond bought was from the early 1900's, will that make the blue diamond more worth $ ??
Dave
Posted by: Dave on August 14, 2007 7:29 PM
these diamonds are beautiful
Posted by: cm on December 6, 2007 7:03 PM
The strong Blue is good for E color?
Thanks
Tarn
Posted by: Tarn on January 11, 2008 6:35 AM
I have a diamond ring that under UV light one of the diamonds glows pink and the others dont appear to golw. But under black light some glow blue and the one that was pink under UV did not show anything. Why is this?
Posted by: Natalie on February 28, 2008 2:48 PM
I have been told by many people that diamonds that glow under a black light are not realy diamonds, but CZ gems.
Posted by: Grace on July 13, 2008 6:18 AM
For a F, Excellent cut, with Medium Blue fluorescence. What is the price downgrade as a percent for the diamond?
Would it exhibit haziness in the diamond? I have taken a look at the diamond and noticed that under natural sunlight it is quite colourless and under indoor light, it may sometimes to have a bit yellow.
Posted by: Pearl on July 2, 2009 10:52 AM