Shedding light on diamond fluorescence
Posted by kingofrocks on July 17, 2008
More and more often we are receiving clients who are not only familiar with “the 4 C’s” of diamond shopping, but are also making their preferences known regarding a diamond’s fluorescence. Unfortunately, a lot of the information they have acquired from their own research as well as from diamond dealers is misleading, conflicting and erroneous. So, what exactly is fluorescence, and how does it affect the appearance and value of the stone?
Fluorescence is a phenomenon that occurs in approximately 20% of gem quality diamonds. A diamond exhibiting fluorescence will literally glow a purplish-blue or sometimes a yellow hue when viewed under an ultraviolet (UV) light source such as a black light. It may also be activated when viewed under natural sunlight, a natural UV light source.
This characteristic in a diamond has been widely used to cast aspersions on other dealer’s stones, as well as to overvalue non-fluorescing diamonds. Typically, the dispensed advice takes the following forms:
- Blue Fluorescence (FL) is bad, stay away.
- 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.
- Strong FL is to be avoided at all costs.
- FL diamonds need to be priced and sold at a discount relative to comparable carat weight, color/clarity-cut diamonds that are non-FL.
The fact is that FL is not a negative, on the contrary it can be and is a positive factor. Several respected members in the trade have known and advocated this position for years.
In 1997, GIA (Gemological Institute of America) conducted an extensive study on the effects of blue diamond FL on visual perception. Both consumers and tradespeople were asked to evaluate the effects of fluorescence 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!
The link to this GIA study is here: http://www.gia.edu/pdfs/W97_fluoresce.pdf
This is a very important study and is recommended reading consumers and should be required reading for all diamond and jewelry professionals. The bottom line? There are no grounds to consider blue diamonds in a negative light and therefore no basis for price differentiation relative to non blue diamonds.
(KingOfRocks.com is a Montreal-based online jewellery retailer focussing on quality diamond and gold pieces, offered at reasonable prices and provided with the very best of customer care. )
This entry was posted on July 17, 2008 at 3:53 pm and is filed under Just jewellery. Tagged: buying diamonds, diamond fluorescense, diamond grade. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
Joe Brandt said
Kudos on a very well-written and carefully researched article; I’ve been maintaining this basic stance for nearly 40 years. Although I agree with the conclusion that (in general) prices for fluorescent vs. non-fluorescent diamonds should not vary, there ARE certain exceptions. I was not present for the GIA visual testing, but I would like to point out that some fluorescent diamonds display certain visual characteristics that differentiate them from others. Firstly, I have seen (on a number of occasions) where a fluorescent diamond (viewed “face-up”) WILL fool the eye (even that of an experienced jeweler) into judging the color to be better than it actually is, sometimes by several color grades. (FYI, diamond color is never graded when viewing a stone face-up.) I consider this to be a positive factor, since a “I” color (or even a “J” color) will look to all the world like a “G” or “H” color when worn in a ring, particularly in daylight. Secondly, some diamonds, especially those that display strong fluorescence, will have a slightly hazy (or “milky”) appearance, which most certainly should have a negative effect on the value, as this may be observed quite easily by the keen observer, both layman and expert alike.
(J.L. Brandt Company, founded in 1928, functions as a consultant to retail jewelers, and provides a jewelry advisory service to the general public.)
kingofrocks said
Honoured to have caught your attention Mr. Brandt. I hope that if we post anything completely erroneous, you’ll be around to set us straight. Thanks for your input on this subject.