Here are some additional things to keep in mind when using short wave UV light to test diamonds:
The color of the fluorescence can vary depending on the type of diamond and the impurities present in the stone.
The intensity of the fluorescence can also vary. Some diamonds will fluoresce very brightly, while others will only fluoresce faintly.
The fluorescence can also be affected by the surrounding environment. For example, diamonds will fluoresce more brightly in a dark room than in a well-lit room.
If you are unsure whether a diamond is real or fake, it is always best to have it appraised by a gemologist.