Fluorescence as a term means that a diamond will glow (in blue) under a UV lamp when illuminated. It was used originally in diamond certifications as additional information for identification, but eventually it began to affect the value of the diamonds.
How does Diamond Fluorescence affect price?
The impact of blue fluorescence on 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. 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.
Diamonds containing fluorescence fluctuate in prices roughly by the following:
| For D to H colors |
IF to VS |
SI1 to I3 |
| Very Strong Fluorescence |
-8% to -12% |
-3% to 0% |
| Strong Fluorescence |
-5% to - 7% |
-1% to 0% |
| Medium Fluorescence |
-2% to - 4% |
0% |
| For I to N colors |
IF to VS |
SI1 to I3 |
| Very Strong Fluorescence |
0% to +4% |
0% to +4% |
| Strong Fluorescence |
0% to +4% |
0% to +4% |
| Medium Fluorescence |
0% to +3% |
0% to +3% |
| Slight to Faint |
0% to +1% |
0% |
