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Diamond And Jewellery Blog | Poggenpoel

What Is Diamond Fluorescence? All the Pros and Cons Explained.

Posted by Johan Poggenpoel on Feb 1, 2019 10:49:26 AM

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If you want your engagement ring to look amazing, it's important to ensure the main diamond is the star of the show and has all the brilliance and fire you would expect from a diamond. 

Fluorescence is a little-known diamond specification that can drastically alter the price and appearance of any diamond you cross paths with.

Mother nature rolled the dice and around 30% of diamonds emit some degree of fluorescent glow when exposed to concentrated UV light. It's random.

As you know there’s UV in sunlight, and although far from concentrated there is a small reaction with the UV light in natural sunlight.

In natural everyday light, even the most experienced diamond graders find it impossible to tell what the fluorescent grade of a diamond is.

Fluorescence can increase the visual appeal of a diamond, or compromise it with bland internal milkiness. Some diamonds are affected (in a good or bad way) and others are completely unaffected and appear identical to diamonds free from any fluorescence. There's no direct correlation. 

How do you determine if a diamond has fluorescence?

Most grading laboratories state the intensity of the fluorescence on the grading report or inside the diamond parcel on a sticker-note.

Cert location 1

Any decent jeweller will have a UV flashlight that will reveal the colour and intensity of fluorescence when pointed directly at a diamond. Blue fluorescence is by far the most common, and what you should be looking for. Orange, green, pink and so forth should be avoided.

For more information on diamond grading laborotories this blog (link) will be a good starting point. 

So, how do I know if the fluorescence grade is affecting a diamond’s appearance?

First of all, it's important to know that diamond fluorescence comes in every colour of the rainbow. The only one that will has an upside is blue. Steer clear from other colours of fluorescence. 

blue fluorescence (1)

*These diamonds are all fluorescing under strong UV light. In normal light, they're all shades of white with no faint hue of colour from the fluorescence. Pretty cool.

Secondly, the intensity of the flourescence will determine the size of the effect, if any.

gia fluorescence scale

*This image supplied by the GIA, clearly shows how a diamond can have a high fluorescent grade, but still look perfectly fine in normal light. 

When a diamond is negatively influenced and you can often spot some cloudiness in the diamond - that’s most probably fluorescence gone rogue. 

At the polar opposite, if a diamond has been positively influenced by this fluorescence reaction, the colour just seems higher. There's not a hint that fluorescence upped the colour you see by a grade or two. Even to very experienced eyes the colour grade simply appears to be higher than that stated on the grading certificate.

For interest's sake; diamonds are graded in very sterile light conditions that don’t contain any UV light waves.

Images of milkiness and how to spot it is discussed a few paragraphs below.

For now, imagine you’re waiting in a police station for your embassy required clearance certificate to go on that long overdue trip to New York.

Two guys with identical clothes walk into a police station and up to a counter.

What would the outcome be? You don’t know.

One might be turning himself in and the other just wants a copy of his ID certified.

We can liken the fluorescence grade to these two gents appearing similar when they arrive. On paper (the diamond grading report) they seem identical. They’re in a police station so you know there might be an issue, but you won’t bet on it.

Once the police officer starts investigating the request and person the outcome and impact on each gent varies drastically. This is the effect of fluorescence. No one assumes everyone walking into a police station is on their way to do some time.

Images like the one below make it out to be an obvious, predictable effect that a diamond looks more dull and milky as fluorescence increases. That’s an oversimplification to the point where it’s noise. It’s just factually deficient.

Fluorescence chart with No

When and how does a diamond benefit from a strong fluorescent grade?

Diamond colours range from D (the ice white cream of the crop) down the alphabet to Z.

Z-colour has a prominent yellow or brown hue. For interests sake a D-colour diamond can cost 10x that of a Z.

The possible effect of fluorescence differs from one colour range to the next.

I J K colour diamonds: Improved colour.

As you saw in the image fluorescence is mostly blue, but it also turns the diamond into a small but expensive glowing bulb of sorts.

Although the effect is much less pronounced in normal lighting conditions, that reaction happens on a mini level and increases the perceived colour by a grade or so in certain colour categories.

Because these diamonds appear whiter than they are in sterile laboratory light, they sell at a small premium. That 2%-5% premium is well spent to up the colour into the whiter territory.

A K-colour diamond with strong blue fluorescence can easily look like it’s somewhere between an I and a J.

Using research on international diamond pricing by the Rapaport Group, these would be the average US$ asking prices for the colours just mentioned.

Price comparrison2

A round brilliant 1,00ct K-colour, VS1-clarity diamond’s average selling price is around $3 220 on the wholesale side. If there’s fluorescence the price will be bumped to around $3 300... but now it appears like a diamond between I and J colour, which when averaged out would cost around $4 400. That tiny premium was money well spent.

Using fluorescence in your favour is a much more affordable way to up the colour a notch. It’s actually a little-known hack.

This colour elevation effect rarely occurs on colours higher than I. 

Although the improvement in perceived colour is rather predictable, these diamonds can still, although rarely, have some cloudiness in them. 

This is one of those nuances that calls for dealing with a jeweller who has very experienced eyes, and can guide you along. Ensure the diamond you choose is crystal clear.

Milkiness appears in grades, sometimes it’s not obvious… until you know what to look out for. You don't have to ram into an iceberg to learn this lesson. 

We curate our diamond stock obsessively to ensure every diamond we sell is free from any detrimental effect of fluorescence. 

D E F colour diamonds: Great Deals.

These high-end colours are most vulnerable to the negative effects of fluorescence.

Keep in mind, many are entirely unaffected by any grade of fluorescence and will appear identical to other options in this range that are free from even a hint of fluorescence.

In bad cases, the fluorescence in D-E-F coloured diamonds can make them look very cloudy and milky. This compromised lustre can be from barely visible to all fogged up inside.

milky vs not milky diamond

*These diamonds are the same size and colour. But it's obvious that fluorescence has compromised the diamond on the left. 

Many buyers in the highest tier would rather pay a premium than figure out this fluorescence topic.  So, the demand for diamonds in these top colours without fluorescence is higher than for those with it. This demand deviance creates substantial pricing differences.

earrings with diamond fluorescence

*A very high end neck-piece where it's clear the diamonds that emit fluorescence have no detrimental effects to their appearance. 

I can easily find you a D-E-F colour diamond with strong fluorescence that’s completely free from any hazy compromises at up to a 30% discount to those without fluorescence. On a 1 carat size that can be over R40 000.

The overseas mega-factories we work with are a call away and know trust in this industry is everything. Every diamond they stock has been evaluated by an in-house gemologist who amongst other things comments on the visual impact of its fluorescence.

Use a knowledgeable jeweller - there are tremendous bargains to be had.

You can view all our diamonds HERE, and please get in touch for any special requests. We import batches of diamonds weekly. 

A tool to help you spot milky diamonds with poor lustre.

By now you know that fluorescence is mentioned on the grading report, but its impact on the stone isn’t.

The collective name for grading cloudiness and milkiness is “lustre”. It has 6 degrees from perfect lustre to obviously poor: L1 - L2 - M1 - M2 - M3 - M4.

Once the lustre dips into M2 - M3 - M4 territory, most grading laboratories would penalise a diamond's “clarity” rating by a grade or two. The clarity grade refers to the type, location and severity of impurities and imperfections in a diamond. Read more on diamond clarities here (link).

For instance, a SI1 clarity diamond will probably be clean to the naked eye. Once you use a jeweller's loupe for magnification the tiny impurities will be visible. If you think a diamond is milky, and you cant find any inclusions - the diamond was probably penalised for the poor lustre.

This method is not foolproof. Another reason to head over to us, where we cover your back… and ours.

Every diamond we sell comes with a 100% upgrade guarantee where you will receive full credit for the diamond you purchased initially towards the upgraded diamond’s price.

I don’t want to buy back milky diamonds as per our guarantee - so we don’t sell them to start off with.

Where to from here?

Please make us your first stop.

It's never too early to reach out, and you'll save yourself a lot of time. 

You're welcome to read the over 200 000 words on this blog, but my whole crew is marinated with diamond knowledge. 

We've got your back. 

Our studios in Pretoria & Rosebank have brilliant full time designers, and you’re welcome to visit us for a session with one of them - no strings attached and zero sales pressure.

If distance is an issue - emails & phone call work better than you would imagine.  

For questions, quotes and consultation bookings please feel free to reach out on info@poggenpoel.com or get in touch via your preffered channel.

Take care. 

Johan Poggenpoel


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Topics: Diamond Investing, Diamond Buying, Diamonds, Comparing Diamonds, Versus, Diamond Colours, Diamond Clarities