Diamond Fluorescence: The Good, the Bad, and the Hazy.

When you expose some diamonds to ultraviolet light, they give off a blue glow. This glow is the diamond’s fluorescence. Up to 30% of all diamonds will have diamond fluorescence. While in 99% of the cases the glow is blue, sometimes it could be yellow, white, or green.

The amount of diamond fluorescence is graded by the GIA as none, faint, medium, strong, and very strong. Diamond fluorescence affects the overall appearance of the diamond. Moreover, it can cause the diamond to appear more colorless or it can cause the diamond to appear hazy.

Diamond fluorescence, is it good or bad?

Whether diamond fluorescence is good or bad depends on its effect on the overall appearance of the stone.

Is faint fluorescence OK in a diamond? Faint or medium fluorescence can cause a diamond to appear whiter than it is. In this case, it would be a good thing.

However, strong to very strong fluorescence causes the diamond to appear hazy. Furthermore, it reduces the amount of light entering the diamond which then reduces the overall brilliance of the stone.

When shopping for a diamond, a faint fluorescence can cause a diamond to appear whiter. This means that you can get the appearance of a diamond that is high on the color scale but for a fraction of the cost.

Are diamonds with fluorescence cheaper?

Just how much you can save on the cost of a diamond depends on the degree of fluorescence. When viewed under normal conditions a diamond with a very strong or strong fluorescence will often appear hazy, this will make a diamond cheaper. A medium fluorescence will only rarely appear hazy. A diamond with a faint blue fluorescence never appears hazy and will be more expensive.

That said, it is advisable to be highly cautious when buying a diamond with strong fluorescence in the D-F color grades. Buyers should also avoid diamonds with a very strong fluorescence in the G-H color grades. These diamonds will not have enough color to neutralize the florescence.

When shopping for a diamond, observe the stone under normal lighting and decide for yourself whether fluorescence negatively affects the appearance of a diamond.

A strong blue fluorescence doesn’t always mean that a diamond’s appearance will be affected.


Carl A. Jones, GIA GG

Carl A. Jones is a GIA Graduate Gemologist with over 20 years of experience in the diamond industry. He is an independent jewelry appraiser. He specializes in determining the value of diamonds and advising consumers on how to buy quality diamond jewelry.

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