A deeper look at fluorescence

Written by barry of ExcelDiamonds.com

Consumers shopping for diamonds both at B&M and with Internet vendors are receiving conflicting and erroneous information regarding the effects of fluorescence on a diamond's visual appearance. The dispensed advice takes the following forms:

1. Fluorescence is bad, stay away.
2. Fluorescence 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 fluorescence is faint or medium, not strong. In higher colors (D-H) it is detrimental; stay away.
3. Strong fluorescence is to be avoided at all costs.
4. Fluorescent diamonds need to be priced and sold at a discount relative to comparable carat weight, color/clarity-cut diamonds that are non-fluorescent

Much of today's consumer attitudes and behavior regarding fluorescence can be traced back to the diamond industry's perception of fluorescence. Briefly, some diamond merchants would look for near-colorless to light yellow diamonds with strong blue fluorescence because they believed that such fluorescence 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 fluorescents also termed "overblues". Gradually this perceived negative impact of fluorescence spread downwards to encompass color grades as far as F. In addition, with the significant influx of Russian goods which contain medium to strong fluorescence into the market, this perceived negative effect of fluorescence has been exacerbated.

Additional industry concerns about fluorescence took on the following perceived factors:

1. Non-fluorescent diamonds were thought to be more pure than fluorescent stones,
2. Non-fluorescent diamonds in the D-F color range were thought to be rarer than fluorescent counterparts, and
3. The hazy appearance in the "overblues" must perchance also exist to some deleterious degree in weaker fluorescent diamonds as well.

A 1993 South Korean TV "expose" on fluorescence aimed at consumers further served to highlight these perceived negative aspects of fluorescence.

Rapaport took these industry notions of fluorescence one step further by codifying these artificially trade induced price differentials into his Rap pricing sheet, thus the diamond 'Bible' had spoken and all say Amen, brother.

The fact is that fluorescence is not a negative in the diamonds; on the contrary it can be and is a very positive factor. Several of us in the trade have known and advocated this both in the trade. We do not price discount our medium or strong fluorescent SuperbCert diamonds as there is no reason to.

In 1997, GIA conducted an extensive study on the effects of diamond fluorescence on visual perception. Consumers and tradespeople were both asked to evaluate the effects of fluorescence on their visual perception and to note any meaningful distinctions between non-fluorescent to fluorescent diamonds of differing fluorescence intensities.

The results of this GIA study were highly instructive and surprising. GIA found that non-trade observers (akin to consumers shopping at their B&M jewelers) could not make ANY meaningful distinctions between non-fluorescent to the fluorescent diamonds and that fluorescent diamonds had no overall effect on the diamond's color or transparency!

For the experienced observers that encompassed tradespeople, the strength of fluorescence 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&Ms and diamond showrooms), diamonds that were described as strongly fluorescent or very strongly fluorescent were, on average, reported to have a better color appearance than less fluorescent stones. Strong fluorescence was reported to have little impact on perceived transparency of the diamonds.

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 fluorescence in a negative light and therefore no basis for price differentiation relative to non-fluorescent diamonds.