So, what is diamond fluorescence?

Fluorescence is a phenomenon that occurs in approximately 20% of gem quality diamonds. A diamond exhibiting fluorescence will literally glow a purplish-blue or sometimes a yellow hue when viewed under an ultraviolet (UV) light source such as a black light. It will also be activated when viewed under natural sunlight, a natural UV light source.

Does fluorescence affect a diamond’s beauty?

That depends. Generally, medium to strong fluorescence will detract from a diamond’s beauty, especially in colourless or near-colourless diamonds. Medium to strong fluorescence will cause the diamond to look oily or cloudy, even if a stone has a high clarity.

In diamonds that are yellowish in colour however, strong-blue fluorescence often ‘whitens’ the look of the otherwise yellow-ish looking diamond.

Does fluorescence affect a diamond’s value?

A diamond with medium to strong fluorescence will bring down the price of most diamonds anywhere from 10%to 30%. The exception to this is in diamonds with more yellow to them (colour K or lower). Medium to strong fluorescence in these diamonds tend to increase their price since they tend to ‘whiten’ their appearance.

What should I take away from this?

As a general rule, stick with diamonds with either no or faint fluorescence. If you’re not sure about a diamond’s fluorescence rating, make sure you ask. It’s a factor that is often not stated on many of the diamond mini-certs that are popular in the diamond trade.