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Diamond fluorescence and how it affects the appearance of the stone

diamond fluorecsence

Diamond fluorescence is a relatively new diamond property added to the already long list of abstract (for the average buyer) things to worry about when choosing a diamond. It is the one that has less significance than the famous 4C’s and some diamond labs don’t even find it important enough to mention it. How important is really the diamond fluorescence?

What is diamond fluorescence?

It is the ability of some diamonds to display luminous colour (usually blue) under UV light. It is important to note that it is not detectable under normal lighting conditions and not all diamonds have it. The embedded video shows two diamonds with same cut size and colour grade with solid difference in the fluorescence display. By GIA standards fluorescence in diamonds is graded with one of the following levels:  none, faint, medium, strong and very strong.

Is fluorescence affecting the appearance of the stone?

Usually not. In many cases even makes the diamond look a grade better in colour. First important note here is that fluorescence grades up to medium never have negative effect on the stone. Grades of strong and very strong sometimes makes the diamonds of high colour appear hazy, however it is not always and not at all for diamonds of colour H and below. This is why if the diamond fluorescence does not affect the appearance of the stone it is not mentioned in some certificates. If the grader think it does he will mention it in the comments section of the report. The diamond fluorescence is always mentioned in GIA certificates, however this does not mean that their opinion is that the appearance of the diamond is affected.


The more I write the more complicated it sounds so here it is in the nut shell. Don’t bother if the fluorescence is graded none, faint or medium. Strong and very strong fluorescence is a bonus if your diamond is colour H or lower. It will give you one colour up in appearance and this might be big savings for bigger stones. Pay attention if the stone is graded strong or very strong and is colour G or higher.  Make sure you can see the actual stone (not buy it online) or have it examined by independent specialist before you buy it.

All diamonds we sale at Kirov JS are taken on consignment (not bought) and carefully examined. Stones with appearance affected in any way by cut, inclusions or fluorescence are returned to the dealer and never offered for sale.