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Diamond Fluorescence - Good or Bad?

Image courtesy of GIA

If you’ve ever shopped for a diamond, you may have come across one that had all the characteristics you’re looking for, but offered at a price below other diamonds of similar characteristics. Upon review of the diamond’s certificate, you notice it has fluorescence. Is this cause for concern or can this really be a great value? To answer this question, you need to know a little more about diamond fluorescence and how it effects the particular stone you’re looking at.

Diamond fluorescence occurs when certain diamonds emits a glow when exposed to ultraviolet (UV) rays from sources such as regular sunlight. This glow can be in the form of a bluish light or more rarely, a yellow or orange light. The fluorescence effect stops once the diamond is removed from the UV environment (while indoors.)

Stuller's Red Box Diamonds

About a 3rd of all diamonds exhibit some degree of fluorescence. GIA considers diamond fluorescence an identifying characteristic; not a grading factor like the 4Cs (color, clarity, cut, and carat weight). GIA Diamond lab reports will describe a diamond’s fluorescence by its intensity from None to Very Strong, and note its color if the fluorescence is Medium, Strong, or Very Strong.

There is a perception in the jewelry trade that fluorescence has a negative effect on the overall appearance of a diamond. Recently, GIA conducted visual observation experiments to study this relationship, where 4 sets of very similar diamonds, covering the color range from colorless to faint yellow, were selected for the different strengths of blue fluorescence. These diamonds were then observed by trade professionals and average observers in various positions and lighting environments. The conclusion was that the average observer (which represented the jewelry buying public) were unable to notice no effects of fluorescence. Even the experienced observers didn’t consistently agree on the effects from one diamond to the next.

Image Courtesy GIA

Sometimes, diamonds within the faint color grades of K-M, bluish fluorescence may make the diamond more expensive because they may appear colorless. However, diamonds with colorless color grades will typically be priced lower, due to the perception that most diamonds with a strong bluish fluorescence will produce a milky or oily appearance in natural sunlight; which is not always the case.

How we do it: We won’t recommend a stone until we’ve been able to verify the stones visual beauty under all lighting conditions, including UV or natural sunlight. If all is OK, a diamond with fluorescence may be a great value indeed.

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