Things You'll Need
Instructions
Hold the diamond in question under a long wave UV light (also called a black light). If the diamond reflects a blue fluorescence, it is most likely authentic.
Be aware that while the majority of diamonds on the market will have a blue glow under UV light, high quality diamonds will not. The UV light method should be performed along with other tests to detect a fake diamond.
Know that cubic zirconia will glow mustard yellow under a UV light. Glass will have no glow at all.
Familiarize yourself with the other methods of detecting fake diamonds, such as the reflection colors within the stone, the weight, the quality of the setting and the wear and tear on the stone itself.
Know that the final word on detecting a fake diamond is a professional appraisal. A certified and experienced gemologist will have the knowledge and skills needed to determine without a doubt that the diamond in question is authentic or a fake.