Did You Know That 2 Diamonds With the Same GIA Cert (and Price) Can Look Very Different? Here’s Why

JannPaul How to Read GIA Cert Diamond Consultation Online

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So you are taking the plunge and looking to buy a diamond engagement ring. Or perhaps you are a big fan of the coveted stone and want to find out more before you blow your entire salary (or more) on it.

In any case, it is very important to do your own research before you buy. Who are the reputable jewellers out there, what does a GIA certification even mean, and do you even understand what a diamond’s 4Cs are? Unless you are very rich, it’s not something you can easily buy off the shelf and replace later.Buying a diamond ring is also not as simple as you think — did you know that 2 diamonds of the same GIA certificate (same statistics) can look very different in real life?

You need to use your eyes, do a comparison with similar-priced stones, as well as use specialised tools to study each diamond before you decide that it’s worth paying for and that you are not sold a dud or being chopped like a carrot.

Here’s some insights to start you on your journey of becoming a diamond expert:

According to jeweller JannPaul, diamonds are not any other luxury branded good such as a Lamborghini or a Louis Vuitton bag, which are immediately recognisable.

Between a “branded” and “non-branded” diamond, there are many factors that affect a diamond’s beauty — much more than what you think (the 4Cs, which will be explained below).

In fact, walking into a branded diamond shop does not guarantee you a beautiful diamond.

To help its customers make the best diamond decision, JannPaul prides itself on providing education — even though this is not a norm in the jewellery industry.

Here’s how JannPaul guides its customers throughout the diamond-buying process (detailed explanations included here):


What is a GIA Certificate and how do I read it?

When a gemological laboratory has assessed the quality of a diamond, it issues a certificate with the diamond’s detailed specifications. There are a few well-known gemological labs — GIA, AGS, IGI, EGL, GSI, and HRD — with GIA (Gemological Institute of America) and AGS (American Gem Society) being 2 of the strictest, reliable and most recognised in the world.

And yes, this does matter, because the lab’s assessment will affect how the diamond is priced. Also, the stricter a lab is, the more accurate the diamond’s paper specifications will be.GIA Diamond Cert 1

Here’s how to read this sample GIA cert:

April 30, 2018 — The date the diamond was certified by the lab.

JannPaul says:  This shouldn’t be more than 3 years ago as the diamond may have suffered wear-and-tear since then, and could be of a lesser value now. If the diamond was damaged, it would not be reflected on the certificate.

GIA Report Number — This is a unique serial number of your diamond that is laser-inscribed on your diamond’s girdle.

JannPaul says: It is absolutely necessary to check the inscription number of the diamond to match its certificate before and after purchasing. This is to prevent any bait-and-switch tactic — there have been cases of private jewellers who would display a better diamond than what’s listed on the certificate. Once the customer makes the purchase, the actual diamond (as per the certificate) is then set onto the customer’s ring.

Shape and Cutting Style — The shape is pretty straightforward, and the cutting style refers to the facet pattern.

Measurements — This shows the length to width (longest to shortest diameter) and depth of the diamond. By dividing the length to width, you’ll get a ratio. 

JannPaul says: For a more symmetrical diamond, this ratio should be as close to 1 as possible. In the example certificate above, the ratio is 7.01/7.05 = 0.9943. If the ratio of the 2 numbers is too far apart, your diamond would appear more oval.

GIA Diamond Cert 2 - grading results

Now moving on to the 4Cs on the GIA cert, which are explained in more detail below:

0.69-and-0.70-price-differenceCarat Weight — How heavy the diamond is, with 1 carat = 0.2 grams.

JannPaul says: Carat is the weight of a diamond. If a diamond is cut too steep/deep, it will appear smaller even though it is of a higher carat weight. It is also recommended to avoid certain flat carat weights, such as 0.30, 0.40, 0.50, 0.70, 1.00, etc. This is due to diamond pricing brackets in the industry. For example, a 0.69ct and a 0.70ct can have a price difference as much as 20% even though it is just a 0.01ct difference.

Diamond HueColour Grade — The body tone of the diamond, best analysed from the pavilion side of the diamond (diamond flat-side down). The lower the colour grade, the warmer the tone of the diamond. For example, E is colourless and H has a very light tint.

JannPaul says: A diamond can come in different colour hues, such as yellow, green, brown, etc. depending on where the diamond is mined from. GIA grades a diamond’s colour by its tone and not its hue. Hence, the GIA certificate won’t indicate if a diamond has a brownish hue. Over 50% of diamonds in the market (branded and unbranded) have a brownish hue. This can only be detected under white light and especially when the diamond is placed against a true colourless diamond. 

This image above shows G Colour graded diamonds, in different hues. Under typical jewellery store lighting, it is almost impossible to see any difference as direct lights would mask the hue colours. However, when you view the diamonds under white light (eg. office lights, outdoor cloudy daylight, etc), these hue colours are very obvious.

JannPaul only accepts diamonds that have a yellow hue, as it is the least obvious colour amongst the others.

Clarity Grade — This refers to the inclusions (inside) and blemishes (surface) of the diamond. The clarity grade starts from flawless and goes to VVS (very, very slightly included), VS, SI (slightly included) and so on. The GIA cert also shows the diamond’s clarity characteristics, AKA the type of inclusions.

JannPaul says: There are many different types of clarity that seem harmless, even for a VS2 diamond. However, these are high-grade clarity diamonds that you need to watch out for and very careful about. Depending on the type and location of the inclusion, it may pose a durability risk on your diamond.

For example, a feather inclusion that cuts across a diamond’s girdle exposes the diamond to a durability risk. An accidental knock where the inclusion is located may end up cracking or chipping the diamond.

In addition, special attention is needed for cloud and pinpoint inclusions. While one type can be a high-value purchase where it’s transparent or translucent, the other can be very detrimental to the overall beauty of the stone. Depending on how dispersed the clouding or pinpoints are, you run the risk of having a diamond that appears chalky/milky, hence ruining the overall beauty of your diamond (it appears less sparkly/bright).

Milky Diamond

These 2 diamonds have the same Clarity grade. However, the diamond on the left has cloud inclusions, which causes the diamond to appear milky.

Diamond Excellent Cut

Cut Grade — This refers to a diamond’s proportion.

JannPaul says: The highest Cut grade on the GIA Certificate is ‘’Excellent’’. However, a diamond with very poor light performance can still be graded as an ‘’Excellent’’ cut as this term is extremely loose. Unfortunately, typical jewellery store lights are LED or Halogen — this makes most diamonds look the same. Furthermore, diamonds with poor light performance are hard to detect as these strong spotlights can mask the light leakages in a diamond.

GIA Diamond - white light and jewellery store lightingHowever, once you bring the diamond outdoors away from these jewellery lights or under white light (office light), the true appearance of the diamond is revealed. A poor performing diamond will appear darker, duller and less brilliant under these realistic everyday lighting environments. In order to avoid poor performing diamonds, you need to check the diamond’s proportions and light performance.

GIA Diamond - White Light

In order to check the proportions of a diamond, a free and useful online tool is the HCA Tool (Holloway Cut Adviser). Key in the values on the diamond’s GIA cert to obtain a final score. The score will range from 0.4 to 10, but the lower the score, the better the diamond’s light performance. To be safe, JannPaul recommends a HCA score of 1.4 or below.HCA Sarine Light Report

However, JannPaul cautions that the HCA tool should only be used as a rejection tool to weed out diamonds of poor proportions.

While a high HCA score means that a diamond has poorer light performance, a low HCA score may not necessarily guarantee that a diamond has good light performance. This is because the Crown and Pavilion angles on the certificate are only average values.

For example, a diamond may have crown angles of 33°, 35°, 35.2°, and get an average value of 34°. In addition, the HCA tool only takes into account 17 out of a diamond’s 57 facets. Hence, a low HCA score does not always translate to a good-performing diamond.

Once a diamond with a low HCA score (good proportions) is found, the next step is to check its light performance. This is the biggest factor in determining a diamond’s brilliance, fire and scintillation.

Aset Scope

The ASET Scope, which stands for Angular Spectrum Evaluation Tool, measures the light return of a diamond. This helps us analyse the diamond’s “fire” (the bursts of rainbow-coloured light when the gem is viewed under a direct light source) as well as the amount of scintillation (the amount of sparkles and flashes when the diamond is moved).

Other items on your GIA cert to look at include Polish (how smooth each facet of the diamond is) and Symmetry (how precise each facet aligns and intersects with one another, which can affect light performance).

For the latter, while a diamond may have Excellent Symmetry, the Hearts & Arrows pattern may not be optically symmetrical. So you need to check your diamond under the Hearts and Arrows scope.

There’s also Fluorescence, which can affect how the diamond looks under UV light or sunlight. Too much of it can make your diamond appear chalky/milky, dull or have an off-colour tint. So most people will opt for a diamond with no fluorescence.

The general rule of thumb is that diamonds with the same GIA certs and triple Excellent scores typically cost about the same in most jewellery stores.


Seeing is believing — don’t just rely on the GIA cert

The GIA cert still remains an important starting point for shortlisting your ideal diamond — at least where price and baseline specifications are concerned. The next step is to use tools and your eyes to compare your shortlisted rocks, under different types of lighting.

For example, JannPaul has done some of the shortlisting for its customers — its Super Ideal Cut diamonds are literally the creme de la creme of diamonds with GIA certs that show a triple Excellent score.

Casey Lai, a co-founder of JannPaul, tells us more: “The Super Ideal Cut term, introduced in Asia by JannPaul, upholds the strictest standard of diamond cuts in the world. However, it is a heavily misused term these days.

“When JP started 10 yrs ago, this standard of diamonds was never seen in the market before and it took the industry by surprise. Over the years, many jewellers have misused and abused the term to sell low-quality diamonds as their own ‘Super Ideal Cut’.

“Unfortunately, the diamond industry is not regulated, allowing any vendors to loosely label their goods. Up to today, we continue to educate our clients so they can make informed choices and not be misled.”

Are you looking to buy a diamond or to find out more about the selection process? Click here to find out more on JannPaul’s website.

Did you know that you can also get an online consultation from JannPaul? The jeweller now has the technology and tools to do so. Contact JannPaul at [email protected] to arrange for an online consultation service.

In-article photos and screenshots courtesy of JannPaul.

Have these insights helped you to make a more informed choice when you are buying a diamond? Let us know in the comments below!

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