Fluorescence, or No Fluorescence in a Diamond? An Ethical Diamond Buyers Guide.

Copyright: GIA and Harold & Erica Van Pelt. Courtesy: Harry Winston, Inc.

Fluorescence is the reaction of trace minerals within the diamond that cause the diamond to glow when exposed to ultraviolet light. In the laboratory, special ultraviolet lights are used to detect fluorescence, but the sun is also a source of ultraviolet rays so a diamond with strong fluorescence will react in daylight as well. About 35% of all diamonds fluoresce. The most common color is blue, and sometimes but rarely a yellow-orange.

The GIA considers diamond fluorescence an identifying characteristic. It is not a grading factor like the GIA 4Cs. GIA Diamond Grading Reports describe a diamond’s fluorescence by its intensity (None, Faint, Medium, Strong and Very Strong) when compared to masterstones used in the lab. If the fluorescence is Medium, Strong, or Very Strong, the color of the fluorescence will be noted.

Some trade professionals think blue fluorescence enhances a diamond’s appearance, especially diamonds with H to M color grades. Bluish fluorescence can make a faint yellowish diamond appear more colorless in UV light, such as natural daylight. As a result, near colorless to faint yellow diamonds with a very strong to medium bluish fluorescence may have a slightly higher per carat price than similar diamonds that do not fluoresce.

The opposite is true for diamonds with higher color grades: diamonds in the D to G color range with a bluish fluorescence are often considered less desirable by the trade. Some believe that a bluish fluorescence may cause a hazy or oily appearance in these diamonds, but only if the fluorescence intensity is very strong. Not all diamonds with very strong bluish fluorescence look oily, however, and they may sell for less than diamonds that do not have blue fluorescence.

The average person will not be able to see fluorescence in a diamond. Here is a quote on detecting fluorescence by the GIA: “For the average observer, meant to represent the jewelry buying public, no systematic effects of blue fluorescence on the face-up appearance of the groups of diamonds were detected. Even experienced observers did not consistently agree on the effects of fluorescence from one stone to the next.”

Simply, blue fluorescence had a negligible effect on the face-up appearance of diamonds in the colorless or near-colorless grade ranges (grades D through J) except for a slight improvement in the rare instances of very strong fluorescence intensity.

Our Diamonds are ethically sourced and most are graded by the GIA. Try our Diamond Search Tool and find your perfect diamond, fluorescence or no fluorescence.