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GIA GTL's Color Grading Of Fluorescent Diamonds

Consumer Deception?

35% Of Diamonds Graded Will Now Potentially Get A Better Color Grade By Fiat Of The Gemological Institute Of America


Martin D. Haske GG, NGJA, MS

The nonprofit Gemological Institute of America had, for over fifty years, taught tens of thousands of jewelers and gemologists what they, the jewelers and gemologists, thought was the proper way to color grade diamonds.  GIA’s own historical teaching record summarized below, said in one way or another, that “diamonds should be graded at their poorer color in artificial light devoid of ultraviolet radiation, rather than at their daylight grade”.

The GIA diamond color grading system, based on these teachings, was, and still is, the implied “standard” used in the United States and most of the world, and in effect has been codified in 16CFR§23, “Guides for the Jewelry, Precious Metals, and Pewter Industries”. 16CFR§ 23.1 Deception (general), states:

                         “It is unfair or deceptive to misrepresent the type, kind, grade, quality, quantity, metallic content, size, weight, cut, color, character, treatment, substance, durability, serviceability, origin, price, value, preparation, production, manufacture, distribution, or any other material aspect of an industry product.”

The framers of these “guides”, without explicitly defining such, necessarily expected that there has been, and is, a respectable and defined, repeatable “standard” within the industry, against which one would “grade” factors such as “color”, which have such a huge economic impact on the price (or “value”) of a consumer item such as a diamond. This implication of repeatability and consistency is paramount to the purpose of the “Guides”, that is, to protect the consumer.  Unfortunately, that does not appear to be the case.

Documented below is fifty years of GIA teaching the trade a relatively consistent method of observing the “color” in diamonds, that is, until 2002, when abruptly, the illumination source quoted is now daylight fluorescent, with no mention of removing the ultraviolet component from this illumination source.  It can be shown scientifically, and is admitted to in the quoted GIA teachings below, that fluorescence, stimulated by ultraviolet, affects perceived color. Any shift to the “white” by adding a blue component to the diamond’s color by stimulating fluorescence, can affect perceived color.  GIA itself, in its 1997 study in Gems & Gemology, stated parenthetically that 35% of a large random sample of diamonds graded had notable fluorescence. If we are now told by implication, that we have to excite the fluorescence by using unfiltered “daylight fluorescent”2002 illumination instead of “cool white, filtered fluorescent light (UV free)”1990 , then any “standards” which the framers of the “guides” thought to have existed (by implication of 50 years of GIA teachings), have been thrown out the window.

It can be easily demonstrated to most people, that color grade shifts of two to three color grades are not unlikely in stronger fluorescent diamonds, but indeed even a one grade shift in the “advertised” color grade, can make many hundreds, to tens of thousands of dollars difference in the price of a diamond, in every level of the marketplace, especially in the finer clarity stones, VS and better.  Going from E to D color, as exemplified in “The Guide” pricing reproduced below for 5 carat stones, can be a very lucrative shift in the wholesale market.On a 5 carat IF stone the E to D pricing difference is $70,000.00!  Even on a 1 carat IF stone the E to D pricing increase is $4,400.00 per carat! It is any wonder why few in the trade would complain about this switch in color grading technique.  However, I wonder what fraction of consumers would complain? How about the FTC?

"The Guide to Wholesale Gem Prices"
Price Per Carat

Used With Permission of  "The Guide"

Appendix A

GIA Diamond Grading Standards
The Historical Perspective

1948 Robert M. Shipley, GIA Course “Gemology, The Science Of Gemstones”, Fourth Edition
 Section 38 The Diamond Color:

The GIA, after long experimentation with various light sources, developed the Diamondlite, which utilizes a standard Mazda bulb with a filter which removes the preponderance of long wave-lengths of light, noncharacteristic of daylight. The resulting illumination differs from daylight somewhat in that the ultra-violet rays are lacking.”

1949 Robert M. Shipley GIA Course “Diamonds”, Volume II Section 32

Page 1:… “Standard conditions of light source and environment, and standardization of methods of color comparison and matching have been established for such commodities such as walnut meats. At the same time, the abuses resulting from the lack of such standardization for diamonds have reached alarming proportions.”

Page 2:…”Daylight, though it is an excellent illumination for distinguishing faint nuances of color when it is good, is not sufficiently constant from day to day, or from one locality to another, to be entirely satisfactory as a standard.  Also, the color of fluorescent stones improves in daylight depending upon its content of ultra violet rays.”

1972 GIA Course “Diamonds”: Assignment 18

…“An instrument for this purpose is the DIAMONDLIGHT(trademark), which utilizes an incandescent bulb with a filter that gives the same balance of wavelengths as north light but with the ultraviolet subtracted. For one who lacks access to a Diamondlite, a fairly effective color-grading light source can be made by using a low-intensity fluorescent fixture with a cool-white tube, filtered through a frosted glass plate, and removed as much as possible from other light sources.”

Page 6: “If the stones fluoresce strongly, they will have a different color in daylight than in artificial light.”

Page 7: “Also, because of the presence of ultraviolet in sunlight, the color of stones that fluoresce blue improves in daylight.”

1978 GIA Course “Diamonds”: Assignment 19

 Page 10: XII. Color Grading Of Fluorescent Diamonds

“Fluorescent diamonds should be graded at their poorer color in artificial light devoid of ultraviolet radiation, rather than at their daylight grade.”

1989 GIA Course “Diamond Grading”: Assignment 10 Grading Color

Page 9 (version E/DY): “Filtered, cool white balanced fluorescent light is best: unlike sunlight, it is nearly free of ultraviolet”

1990 GIA “Diamond Grading Lab Manual”

Page 10 (version H/YA): “Use cool white, filtered, fluorescent light (UV free) in a darkened room”

1995 GIA Course “Diamond Grading”, Assignment 10

Page 9 (version E/DY): “Filtered, cool white balanced fluorescent light is best: unlike sunlight, it is nearly free of ultraviolet” {Note that the grade is grading at the bottom of the DiamondLite, where any UV present in the bulbs used would have the minimum impact on color grade perceived}


1997 Gems & Gemology Winter 1997, “A Contribution To Understanding The Effect Of Blue Fluorescence
On The Appearance Of Diamonds”, Thomas M. Moses, Ilene M. Reinitz, Mary L. Johnson,
John M. King and James E. Shigley

· Page 248:  “The data revealed that approximately that approximately 65% of these diamonds {26,010 GIA GTL grading reports} had no reported fluorescence to long wave UV radiation.(Note that a report description of ‘none’ means that any fluorescence exhibited is weaker than that of the reference stone that marks the none/faint boundary.)” {Comment: This is a convenient, trade beneficial, consumer be damned, redefinition of the word “none”.}

· Page 248: “Of the 35% (9,175 diamonds) for which fluorescence was reported, 38% (3,465) were reported as having faint fluorescence and 62% (5,710) had descriptions that ranged from medium to very strong.”

· Page 248:  Figure 2 shows the Gem Instruments Long Wave / Short Wave ‘booth’ in use, with the long wave lamp closest to the viewer and furthest from the diamond(s). “At GIA/GTL, the diamond being examined is placed table down and moved between the fluorescence reference stones until the intensity of the fluorescence is stronger than the reference stone on the left and weaker than the reference stone on the right.” {One might note that if one were to turn the light around (cord on left) such that the long wave lamp were on the bottom, then you would experience a greater UV luminance on the diamond.}

· Page 251: Table 2 shows five viewing environments:

1. DiamondLite, in a darkened room, Verilux type fluorescent tubes(2)
2. Overhead desk-mounted light in a lighted room, 18” Phillips F15T8/D 15-watt fluorescent tube
3. Overhead desk-mounted light in a darkened room, 18” Phillips F15T8/CW 15-watt fluorescent tube
4. Ceiling mounted room lighting, Phillips FB40CW/6 40-watt fluorescent tubes
5. Window (indirect sunlight), South daylight (1:00-4:00), July, in New York City
{What about UV free cool white, taught for 40 plus years?}

· Page 252:  “Because different intensities of ultraviolet radiation in the light sources could affect the diamonds’ fluorescence reaction, we used a UVX digital radiometer manufactured by Ultraviolet Products, Inc., to measure the UV content in each of the light sources chosen, The measurements revealed no appreciable differences in long-wave content from one fluorescent light source to the next. According to our measurements, indirect daylight through our windows has about as much UV radiation as the fluorescent light sources.” {Comment: evidently the test designers never heard of north daylight, nor of fifty years of teaching, “filtered cool white, devoid of ultraviolet”.}

· Page 255: “In other words, there did not appear to be any difference among the light sources we used in their effect on perceived color relative to fluorescence.” {Comment: given that each light source above had the same measured UV content, would you expect any difference?}


2002 GIA Course “Diamonds and Diamond Grading”

Page 15: “The most widely available and accepted lighting for color grading diamonds is balanced, daylight equivalent, fluorescent light” {Comment: no mention of UV free, as in the last 50+ years.}

2002 Diamond Grading 13, Page 14

{Oh, a strong blue! Lets get a better color grade!}

{Comment: The subtlety here is that you are maximizing the influence of UV on the diamond being graded. Compare this technique to that of the picture shown previously from the 1995 Diamond Grading course Assignment 10.}

New Bulbs Versus Old


Colors Of Fluorescent Lights

Verilux Bulbs (from 9/26/02)


Note UV Response Of New Verilux Bulbs


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