Diamond Fluorescence

Diamonds have many unique properties, including natural blue fluorescence under any source of ultraviolet light. Fluorescence is a phenomenon which causes some diamonds to glow under ultra violet light (UV), which is abundant in natural daylight and some artificial lighting.

The following are the possible grades given to fluorescence: Faint, Medium, Strong, Very Strong.

All grading reports denote the diamond’s fluorescence as well as color. It is estimated that 20%-25% of all diamonds have some degree of fluorescence. Most often diamonds will fluoresce blue, but occasionally yellow or green or an unusual color may occur.

The Gemological Institute of America's Gem Trade Laboratory, the country's leading diamond grading lab, lists fluorescence as an identifying characteristic, not a grading factor. And based on a GIA GTL random sample of data for 26,000 diamonds, diamonds with fluorescence are more rare than nonfluorescent stones: 65 percent of diamonds have no reported fluorescence. Listed below is GIA's list of abbreviations for strength of fluorescence as well as their meanings:

• N : No Fluorescence
• F or FB : Faint or Faint Blue Fluorescence
• SL : Slight Fluorescence
• M : Medium Fluorescence
• S : Strong Fluorescence
• EF : Extreme Fluorescence

Strong fluorescence can cause a diamond to look hazy or less transparent, however this is not always the case. Years ago the term "blue white" was used to describe the finest of diamonds, many of which had bluish overtones caused by fluorescence. Unfortunately the term became misused and seldom accompanied a diamond that was truly white or blue. It is not appropriate to use the expression in modern times unless the diamond truly possesses a bluish hue.

Fluorescence is the caused by trace impurities in the diamond. Approximately one-third of all gem-quality diamonds fluoresce, usually blue, But white, yellow, green, orange, and very occasionally red also may be witnessed. Pink diamonds may fluoresce a bright orange.

Effect of fluorescence on diamond color:

Fluorescence is a characteristic that makes some diamonds appear to change color when they are exposed to the ultraviolet light that surrounds us every day in sunlight, and in the light produced by fluorescent bulbs.

• The higher (colorless) grades, D through F, will be adversely effected by fluorescence. They will appear milky or oily.
• The middle grades, G through I, appear to have some tolerance for fluorescence. Mild to moderate amounts of fluorescence can be acceptable. However it is advisable to shy away from strong fluorescence with these color grades. Personal taste in the appearance of your diamond is suggested here.
• The lower grades, J through M, can actually have their appearance improved by fluorescence. The blue of the fluorescent light, and the yellow tint from the diamond will have a tendency to cancel each other out, allowing the diamond to look whiter.

Impact of diamond fluorescence on diamond price:

The impact of blue fluorescence on diamond price depends on its noticeability. For some higher color stones, fluorescence gives the stone a milky white appearance, which greatly lowers value. In some instances, the fluorescence is hardly noticeable and has minimal impact on the stone's brilliance and value. Fluorescence often adds value to lower color stones as it gives the stones a whiter, brighter appearance.

It is common to find that diamonds with colorless grades (D-E-F) or near colorless grades (G-H-I-J) are lower in price when they exhibit fluorescence and faint yellow grades (K-L-M) are higher in price when exhibiting fluorescence.

A strong yellow fluorescence will brings prices down, sometimes quite a bit, since yellowish tinted diamonds are generally less desirable than whiter stones. A blue fluorescence can help increase the prices of diamonds with yellowish tones.

Some buyers regularly pay better prices for highly fluorescent "I" color and lower stones. Yellow fluorescence may require an additional 5 to 10 percent discount. Generally, the higher the quality and price per carat the more strong fluorescence lowers value.