Until relatively recently, fluorescence in a diamond was something that only gemologists and geologists paid attention to. For most of the jewellery buying public, the traditional 4C’s, as defined by the GIA (cut, colour, clarity and carat) were enough to decide whether a diamond was of an acceptable quality or not. In 1997, the GIA conducted a comprehensive study on diamond fluorescence and the associated effects on appearance and colour.

In the current information era we live in, it’s easier than ever to “research” topics on the internet, but as is the case in most instances, a little information can be dangerous. Fluorescence is perhaps the most misunderstood diamond property and many diamond shoppers express concern about fluorescence, without necessarily knowing why, or stopping to consider if their concerns are valid or not.

As you probably know by now, Katannuta Diamonds are big proponents of diamond education, so in this post we’ll be giving you all you need to know about diamond fluorescence. Is it a good thing? Is it a bad thing? Does it make your diamond less valuable?

What causes fluorescence in diamonds?

Fluorescence occurs when a diamond contains a trace amount of an element that reacts under UV light. Whilst diamonds are single element gemstones, made of virtually exclusively of carbon, minute traces of aluminium, boron and nitrogen may exist within a diamond. These parts per million (ppm) and parts per billion (ppb) concentrations cause diamonds to fluoresce. It’s also worth noting that rare blue diamonds are a result of boron imperfections and the yellow colour in diamonds is a result of nitrogen.

Fancy colour diamond

In the case of this natural, fancy deep yellow diamond, the strong yellow fluorescence actually enhances the yellow colour visible in the diamond.

Is diamond fluorescence common?

Most natural diamonds don’t fluoresce. The 1997 study by the GIA showed that only 25-35% of the 26,000 diamonds they examined showed any sign of fluorescence. Fluorescence is only visible when the diamond is viewed under an ultraviolet light and blue is the most commonly exhibited colour. Other recorded fluorescence colours include yellow, orange, white and green. If a diamond being certified by the GIA does fluoresce under a UV light, the GIA certificate will note the intensity of fluorescence exhibited (none, faint, medium, strong or very strong).

Non fluorescent diamond

A diamond with no fluorescence (left) and a diamond with strong blue fluorescence (right), viewed under an ultraviolet light.

Can you see the effects of fluorescence in a diamond?

Just as each diamond is unique, the effect of fluorescence in each diamond is unique too. In general, diamond fluorescence has no effect on the stone’s colour grade. It has been noted that near-white and slightly tinted diamonds (those in the I to N colour categories) can appear more white if they show medium to strong blue fluorescence. If you are looking at top colour diamonds, those in the D, E and F range, very strong fluorescence may result in the stone looking milky, or oily. This is the exception rather than the rule, however.

During its 1997 study, the GIA concluded, “For the average observer, meant to represent the jewelry buying public, no systematic effects of blue fluorescence on the face-up appearance of the groups of diamonds were detected. Even experienced observers did not consistently agree on the effects of fluorescence from one stone to the next.” Quite simply, blue fluorescence had a negligible effect on the face-up appearance of stones in the colorless or near-colorless grade ranges (grades D through J) except for a slight improvement in the rare instances of very strong fluorescence intensity.

M colour diamond

This bespoke Katannuta Diamonds engagement ring was set with an M-colour diamond with strong yellow fluorescence, yet the gem is near-white in colour to the naked eye.

Does fluorescence affect diamond prices?

The effect of fluorescence on prices is very dependent on the colour of the diamond, and the strength and colour of the fluorescence. For D, E and F colour diamonds, strongly fluorescent stones may sell for 3-5% less than stones with no fluorescence. Blue is the complimentary colour to yellow and, as such, blue fluorescence can make an I-M colour diamond appear whiter. Due to this, I-M gems may sell at a slight premium when they possess Medium to Very Strong fluorescence.

Is fluorescence a good thing or a bad thing?

Fluorescence is one of those subjective topics that people may never agree on. For the most part, the effects of fluorescence are so negligible that it shouldn’t be a major consideration in your diamond buying process. Diamonds are an emotional purchase symbolizing love and commitment and you’ll fall in love with the right diamond the moment you see it. If that stone happens to have some fluorescence in it, so be it. If that diamond doesn’t fluoresce, that’s ok too. It’s a personal choice.

We’ve sold diamonds to geologists who have specifically asked for strongly fluorescent stones, because they understand the unique science behind the colours. Ultimately, fluorescence is neither good, nor bad – it just is. If you make sure that the diamond you are purchasing shows no signs of having a milky or oily appearance, you’ll be good. Paying attention to the cut is far more important, because that is where your fire, sparkle, brilliance and scintillation will come from.

D colour diamond with fluorescence

We manufactured this ring for a geologist client of ours, who specifically wanted a diamond with blue fluorescence. The stone is a D-colour, yet shows no signs of any visible effects of the strong blue fluorescence when viewed under normal lighting conditions.

At Katannuta Diamonds we know that purchasing a diamond is a huge commitment and we know you want to get the best you can afford. We are here to guide you through the process of deciding on the best gem for your budget, taste and ring design. We encourage clients to set an appointment to look at available diamonds in person, and to compare different colours, clarities and levels of fluorescence, before settling on a diamond that speaks to your heart. Give us a call on + 27 (0) 832340247 or contact us via our website to enquire about our extensive range of loose diamonds. We’ll guarantee you better prices than your big name retail stores could ever offer you!