Diamond Fluorescence: What It Is and When It Matters

Fluorescence is one of the more misunderstood lines on a diamond certificate. It is not a flaw, and for most buyers it changes nothing you can see. Here is what it actually is, how the scale works, and when it is worth a second thought.

What fluorescence is

Fluorescence is the soft glow, almost always blue, that some diamonds give off when they are exposed to ultraviolet light, such as sunlight or the UV lamps in some clubs. It is caused by trace elements in the diamond. Around a quarter to a third of diamonds show some degree of it. In normal indoor and daylight, most people never notice it at all.

The fluorescence scale

Labs grade fluorescence from None up to Very Strong:

When fluorescence helps

In diamonds with a faint warm tint, lower on the colour scale, a little blue fluorescence can cancel that warmth and make the stone look a touch whiter. For those stones, faint to medium fluorescence is sometimes seen as a small bonus.

When fluorescence hurts

At the Strong and Very Strong end, a minority of diamonds can look slightly hazy, milky or oily in bright sunlight, which takes away from the crisp sparkle you are paying for. This is uncommon, but it is the one scenario worth avoiding, and it matters most on already colourless stones where there is no warmth to cancel.

Varniya's stance

Because every Varniya diamond is already DEF colourless, there is no warmth that needs cancelling, so fluorescence offers no upside and only carries the small risk of haziness at the strong end. For that reason Varniya favours diamonds with None to Faint fluorescence, and never accepts a stone whose fluorescence causes any visible haze. Combined with our Ideal cut and VS1-and-above clarity, that keeps every stone crisp and bright in any light.

FAQs

Is diamond fluorescence bad? Not in itself. Faint and medium fluorescence have no visible effect, and a little can even help lower-colour stones look whiter. Only strong or very strong fluorescence occasionally causes haziness.

What fluorescence should I choose? For a colourless DEF diamond, None to Faint is the safe choice, which is exactly what Varniya stocks. There is no benefit to stronger fluorescence on an already white stone.

Next: Diamond Clarity. Back to Diamond Buying Guide.