Blue fluorescence impact on color and value:
A diamond that reflects a bluish glow when excited with UV light has 'blue fluorescence' and this phenomenon is triggered by the amount of boron and nitrogen present in each diamond.
The intensity of fluorescence is measured and defined by the GIA as follows:
None [NN]; Faint [FT]; Medium [MED]; Strong [STB]; Very Strong [VSB].
Faint and medium fluorescence is not detectable to the naked eye and is simply a noted characteristic with little impact on value.
Medium fluorescence in colors D to H should lower value modestly (approximately 3%.)
However, blue fluorescence in I to K colors actually increases the diamond’s value (3-5%) because these colors appear whiter when they have blue fluorescence present.
'Strong blue' fluorescence may have little effect on brilliance of certain diamonds and in these stones the impact on value should be modest (5-10%.)
If however a 'blue glow' is clearly visible to the naked eye, value drops dramatically and one should exercise caution before buying.
Diamonds with 'very strong fluorescence' that appear cloudy have very little value and should be avoided. Learn More >