DIAMOND FLUORESCENCE

GIA Fluorescence Grading Scale

1. Diamond fluorescence is technically speaking: the emission of energy in the form of light by a diamond as a result of its simultaneously absorbing radiation of another wavelength. The electrons of some diamonds are excited by the radiation and emit the excess energy in returning to their original state. 

2. This emission, unlike phosphorescence, ceases as soon as the source of excitation is removed, and so the glow disappears when removed from an ultra-violet light source. 

3. Fluorescence is a naturally occurring phenomenon in diamonds and other gemstones. If it is present in a diamond, it cannot be removed and if a diamond does not fluoresce, it cannot be induced into the stone. The fluorescence that occurs in a diamond arises from submicroscopic structures within the diamond when it is exposed to invisible UV light. 

4. Blue is the most common color of fluorescence but other colors such as yellow, green, orange and white are also found. 


Diamond Fluorescence and its Effect on Value

1. Diamond fluorescence in colors other than blue can have a very negative impact on value. That is because fluorescence in these colors will make the color of a diamond appear to be darker, more yellow or more "fuzzy" under light that includes ultraviolet radiation. 

2. Knowledgeable diamond dealers will discount the value of these stones by up to 50%. 

3. Blue fluorescence can have both positive and negative effects on both the appearance of a diamond and its value. 

4. "Faint Blue" or "Medium Blue" fluorescence can enhance the apparent color of a diamond under many lighting conditions, making it look whiter than it really is. There is no premium for these diamonds. 

5. On the other hand, diamonds with "Strong Blue" or "Very Strong Blue" fluorescence can appear "milky" or "cloudy" in these lighting conditions. The value of the later diamonds can be discounted by the trade by 20% to 50%. 

THE DIAMOND FLUORESCENCE HONESTY GAP

Since certain fluorescent diamonds can be far less expensive than similar stones that do not fluoresce this price difference can be exploited by some dealers.  Some dealers purchase inexpensive highly fluorescent diamonds then market the fluorescence as a positive.  While not exactly dishonest they do deliberately prey on the lack of knowledge on the part of the consumer to make an easier or a larger than normal profit.