Dismantling the fluorescence stigma

Rachael Taylor

Diamonds with this trait may fetch lower prices on the market, but some in the trade are embracing the opportunities they offer.

With an inconvenient leading letter, fluorescence falls outside of the 4Cs. Yet that hasn’t stopped it from becoming an essential element when it comes to haggling the price of diamonds.

In the grading world, fluorescence refers to “the visible light some diamonds emit when they are exposed to ultraviolet rays,” according to the Gemological Institute of America (GIA). Most of the time, the light is blue, though occasionally it can be white or yellow (see box).

“The first thing you do when you tip out a parcel of diamonds is put it under the flou lamp to see how highly flou it is,” admits Satta Matturi, founder of rough-diamond-buying service Ideal Luminescence.

While GIA studies show that this trait has no noticeable effect on a diamond’s appearance in the vast majority of cases, “diamantaires have generally looked down upon fluorescence” as reducing the stone’s value, notes Eddie LeVian, chief executive of American jeweler Le Vian.

Indeed, most industry buyers latch on to this diamond feature as a gateway to lower prices. The Rapaport Price List has a section dedicated to the discounts one can expect for diamonds with blue fluorescence. Depending on the stone’s color and clarity, the discount can be as high as 25% if the fluorescence is very strong, or as low as 1% if it’s faint (though lower colors may have no discount at all).

Why the bad rap?

Despite the stigma, there is little science to back up claims that fluorescent diamonds are inferior stones. Fluorescence is a commonplace trait, occurring in somewhere between 25% and 35% of all diamonds, according to the GIA. Only 10% of these would have a grading classification of “medium,” “strong” or “very strong” fluorescence — the levels that the lab says “may impact appearance.”

One of the most serious — and popular — criticisms is that fluorescence can cause diamonds to look milky. Yet the GIA reports that fewer than 0.2% of the fluorescent diamonds it’s received for testing have appeared “hazy or oily” as a result of the fluorescence, so that phenomenon is incredibly rare.

There is a perception that fluorescence affects the value of a diamond, and I think that is probably true,” comments gemologist, dealer and gemstone educator Eric Emms. “Whether that is fair or not is a moot point.

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Source Rapaport

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