Diamonds that belong to a group called type IIB tend to appear blue. However, after absorbing high-energy light, such as UV light, these diamonds can emit a residual glow for a short period of time. This phosphorescence can vary in color from blue to pink and fiery red, depending on the diamond. Fluorescence in diamonds is the brightness that can be seen when the diamond is under ultraviolet (UV) light.
Approximately 30% of diamonds will shine under UV light, and the GIA rates diamond fluorescence as None, Weak, Medium, Strong and Very Strong. When some real diamonds are subjected to a dark room with ultraviolet light, they can give off a certain glow. This is due to a phenomenon called fluorescence and approximately 35% of natural diamonds show some degree of this effect. In nature, the presence of certain chemical impurities within the diamond composition triggers this brilliant effect in the presence of an ultraviolet light source.
The diamond may appear to glow purple under a black light because the source itself looks a little violet. Interestingly, diamonds can also glow under black light in a variety of other colors ranging from yellow, white, red, green and orange. First, you can check the authenticity of the diamond you have by matching the inclusions to the clarity graph of the diamond. Keep in mind that cut quality determines the brilliance of a diamond and not its ability to shine in low light conditions.
Another practical benefit of buying a diamond with fluorescence is that it can help improve the color appearance of diamonds in the lower color ranges. When it comes to choosing your diamond, it's best to approach fluorescence in the same way you approach other diamond characteristics such as shape. They have a specific line of diamonds called “Brian Gavin Blue” that offers exceptional diamonds with medium and very strong fluorescence intensities.