Diamond fluorescence is a unique phenomenon that occurs in certain diamonds when they are exposed to ultraviolet light or x-rays. This ability to glow can be seen with gemological instruments or under black lights, such as those found in nightclubs. It's important to note that fluorescence is a relatively rare occurrence, with only 25 to 35 percent of diamonds exhibiting this trait.

It's worth pointing out that the fluorescence of a diamond does not affect its color grade under normal lighting conditions. However, some studies suggest that when viewed face-up, a strong blue fluorescence can make some diamonds appear better than similarly color-graded diamonds with no fluorescence. This is because a strong blue fluorescence can mask faint and very slight yellow color grades, making the diamond appear more colorless.

When discussing diamond fluorescence with customers, it's essential to note the various colors and intensities in which it can appear. Blue is by far the most common, but it can also appear in other colors. Fluorescence is noted on certified diamond reports as none, faint, slight, or strong, with some labs using the descriptors "very faint" or "very strong."

While fluorescence does not affect a diamond's fire, brilliance, or durability, it can have an impact on its value. At the higher end of the D-to-Z color scale, the phenomenon can sometimes make a diamond look slightly milky or hazy, which can reduce its value. However, in some cases, the fluorescence can actually be beneficial, as it can make a diamond appear more colorless and improve its perceived quality.

It's important to disclose any fluorescence to customers, even if they are unaware or uninterested in the phenomenon. This is because some customers may be upset if they discover that a stone they bought suddenly glows on the dance floor. Additionally, it's crucial to note that fluorescence is not an identifying characteristic of natural or synthetic diamonds, and some CZs can also exhibit fluorescence.

In conclusion, diamond fluorescence is a fascinating phenomenon that can add to the beauty and perceived quality of a diamond. However, it's essential to educate customers about the various aspects of fluorescence, including its rarity, colors, and intensities, as well as its potential impact on a diamond's value. By doing so, jewelers can help their customers make informed decisions and avoid any misperceptions or misunderstandings.