What is Fluorescence in a Diamond?

• Gem-quality diamonds that emit light when exposed to long-wave ultraviolet light. B

What are the Gradations of Fluorescence set by the Gemological Institute of America?

• N: No Fluorescence
• F/FB: Faint/Faint Blue Fluorescence
• SL: Slight Fluorescence
• S: Strong Fluorescence
• EF: Extreme Fluorescence

Why is Fluorescence Bad for a Fine-Quality Diamond?

• Fluorescent diamonds, especially the extreme rare cases known as overblues, give a diamond a visible haziness that undervalues them on the market.
• They appear almost cloudy in light with strong ultraviolet content, which compromises their clarity and decreases their appeal.

Why is Fluorescence Good for Diamonds of Lesser Worth?

• Strongly fluorescent diamonds with yellowish body color have the appearance of better, whiter color in sunlight, a source of ultraviolet light.
• These lower-color diamonds with powerful fluorescence often command a premium.

Fluorescence Put to the Test by the GIA

• Fluorescence in diamonds is considered rare. 65% of diamonds have none.
• Strongly blue fluorescent diamonds possessed better color grade in the face-up position.
• No fluorescent effect was observed in the table-down position, which is how labs color grade diamonds.
• Color fluorescence was more apparent in diamonds grades I through K.
• Strongly or very strongly fluorescent diamonds were considered to have better color appearance than less fluorescent stones.
• Blue fluorescence had little effect on transparency.
• Overblues are rare, so they were not included in the GIA study.
• The GIA conclusion: fluorescent diamonds are stigmatized needlessly, which puts a negative impact on their salability.
• Fun factoid: The famous Hope Diamond fluoresces an extremely unusual red-an occurrence in blue diamonds-and this has influenced the legend of its curse.