Diamond Education

Diamond Fluorescence

Fluorescence is the visible light that some diamonds emit when exposed to ultraviolet radiation. On a report, it is a description of the diamond's response under specified conditions.

It is not another name for clarity, and it should not be read as a universal good-or-bad quality label.

What the report describes

GIA's fluorescence terminology addresses the intensity of a diamond's reaction to long-wave ultraviolet light. Reported categories commonly include None, Faint, Medium, Strong, and Very Strong. A reaction may also have a stated color.

The visible emission lasts while the diamond is exposed to the relevant ultraviolet source. Its presence alone does not establish whether a stone is natural or laboratory-grown.

Does fluorescence change appearance?

GIA research indicates that fluorescence has no widely noticeable effect on appearance for the overwhelming majority of diamonds. Some individual stones require closer consideration under relevant viewing conditions.

Rather than assuming a category predicts your personal experience, view the actual item and ask about any specific appearance concern.

Avoid simple rules

A statement that all fluorescent diamonds are undesirable is too broad. So is a statement that fluorescence always improves appearance. A report field should be interpreted alongside the stone's other information.

If haze, transparency, or a visual effect concerns you, describe that concern directly. Do not assign a cause from a single report word.

Compare in a useful way

Ask to see the stone under more than one ordinary lighting condition and understand whether ultraviolet light is relevant to the demonstration. Compare the same item and keep the complete report available.

If buying remotely, request an explanation of the viewing conditions used for photographs or video. Dramatic lighting can show an effect without establishing how the diamond will look in everyday use.

Use fluorescence as information

The most useful approach is to read the field, understand what it describes, and investigate any question about the individual diamond. It is one part of a complete description.

Further reading: GIA: About fluorescence