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Diamond Essentials

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Diamond grading

Our 6 C citeria in Diamond Grading explained


You certainly have heard about the 4 C's in traditional diamond grading.
Everything is about

Carat Weight

But which ones should you value most?

Are there any other criteria, influencing the value of your diamond?
Antje Paul-Kessel is the owner of the e-boutique Noemi Diamonds, jewelry designer, gemologist and member of the international international diamond trade network. She explains to you with this hands-on-guide what you should know- before you buy a diamond.

Buying a natural diamond is always a long- term investment.

Therefore, two new trends in the trade and society play a role in the future evaluation of the diamond which you buy today:




The 5th C: Consciousness

will secure the long-term value of your diamond


Conflict- free is good, transparent origin is better

Consciousness, or otherwise also called as responsible sourcing of diamonds, such as conflict-free diamonds, ethical mining, sustainability policies of mining companies is in the mind of many jewelry lovers. The diamond trade established the KP (Kimberley Process) to eliminate conflict diamonds. Conflict regions come and go; some areas develop peacefully over time. However tight or not the KP control might be, continuous, seamless monitorings needs still need to be in effect at each stage of the value chain.
The focus has now turned towards the environment. Mining of natural diamonds is in the middle of Nature and very often, at the end of the inhabitable world. A few rare species and plants are living amazingly in those remote areas of the world, perfectly adapted to a harsh environment. Lovable creatures like karibu, mammals, fish and other species and their fragile habitat need to be protected.

Purchasing a diamond from other than clean mining will affect the long-term value of your diamond. Buying a diamond without knowing its origin is a considerable risk now. It could undermine the longterm value of your diamond without even that you might realize it. The ongoing awareness for conflict diamonds is still in our mind and influenced massively the evaluation of diamonds over the past years. The same is likely to happen with the environmental awareness, which is receiving more and more wind from the side of activists and global political movements.

The branch organization Rapaport established a classification of investment diamonds with some grading criteria. An investment diamond is, if you want to choose a synonym, a diamond worth your money. At this moment, Rapaport excludes diamonds from the Marange fields in Zimbabwe, Africa. They are rejected to be investment diamonds. The humanitarian problems of Zimbabwe are not yet resolved and diminish the value of their diamonds in the international community. Other countries could follow the Marange diamonds into the ban, for the same or for different reasons. With the consequence that these diamonds would plunge significantly in value.

Could the origin of diamonds be hidden? Yes and No. On the paper, yes. But from scientific investigation, no. Particular diamonds bear the characteristics of the Earth where they come from, and this becomes visible in detailed gemological assessments. We can expect full traceability of diamonds in the nearby future. 

At Noemi, we disclose the source of diamonds to our customers and we advocate to phase out diamonds with no description of origin.


Which origin is o.k. for diamonds?


The leading diamond- lab GIA now offers an additional origin- report. That means that the consumer can trace the diamond down to the mine when GIA has received it as a rough diamond first. We have a strong preference for diamonds from controlled mining. Controlled mining implies that a mining company has funds to invest in environmental and social efforts to improve actions for more sustainability and better social care. 

The laws of the country play a significant role in environmental protection. Canada has stringent requirements regarding ecological responsibility. 


We offer diamonds from miners with enhanced, verifiable ESG reporting. 

Family run- mines can be considered from case-to-case and for fancy colour diamonds, the Argyle mine in Australia offers origin- reports with transparency to shareholders.


Responsible trademarks 

  • Canadamark (TM) 
  • Argyle (TM).
  • GIA Diamond origin report (TM)
  • The Rapaport Diamond Certficate (TM)


Initiatives in traceability

Natural diamond producers have founded a project Tracr to follow down the diamond to its origin by blockchain. The blockchain company Everledger implements already blockchain applications for large consumer groups in Asia.

Some mining companies are making progress in the integration of blockchain technology.


Please have a look at our consciously sourced diamond offers (main menu).


The 6th C: The Certificate

It secures the value of your diamond


 Did you know? Professionals buy diamonds "on paper", only based on the grading report, they don't need necessarily to look at it. 

It is sometimes inevitable to examine a stone with one's own eyes. But, in case of a sealed stone with a GIA report, it is often not necessary. 
The condition for this confidence is, of course, that the report is of a highly-reputed gem-lab. The international diamond trade tends to rely on the elite- standards of four diamond-grading labs: GIA, HRD, IGI and recently also AIG.
GIA (Gemological Institute of America) is the leading authority, as it offers the broadest service and invests in education and research. Especially when it is about the top-class of diamonds, as we are offering in our e-boutique, the high value of the diamonds would not justify any risk to miss the boat with a certificate of low quality. The best resell- value for the consumer comes from GIA reports, followed by HRD (an independant subsidiary of the Antwerp World Diamond Centre) and the fast- working AIG as a newcomer. IGI represents an acceptable standard of grading, too, and is now in the ownership of a Chinese group.
We do not recommend diamonds of other grading standards, except for SSEF and Gübelin, two Swiss companies.
So, briefly, how much a diamond grading counts, is influenced by its report issuer.

The Rapaport diamond certificate requires a GIA lab- report and is therefore a double grading (first by GIA and then by Rapaport). If you own an investment grade diamond now, it could be eventually interesting to perform an additional grading as investment diamond.

If you own already diamonds, we recommend to renew the lab- reports from time to time to keep it up-to-date and valuable. 



The 4 C's in one model

The graph shows the virtually pictured multi-layered "price engine" of a diamond. The four propellers C- Carat, Colour, Clarity, Cut turn each of them the price either to a higher or lower value. Their different quality antipodes drive the dynamic range of diamonds of commercial gem- quality. The lows and highs have a common range in jewelry. In Colour, the exceptionally high quality is the colour D, for the lower end it is J. For the Clarity it is from FL/IF- (Internally) Flawless (high quality) to SI (Slightly Included). For the Cut, it is from Ideal/ 3x Excellent (Triple Ex) to Good as a low but under the circumstances considerable quality. And the Carat size propels the diamond to a higher value or lesser value, too.

Did you know? For a 1 Carat Round Brilliant diamond, the lowest quality which a professional would probably advise would be a J Colour, Good Cut, SI2. At the other hand, the best quality customers can get like a 1 Carat would be an Ideal Cut/ Triple Ex, D-Colour, IF/ FL (Flawless) diamond. Consider both the diamonds would have a GIA certificate.  

The price difference for a 1 Carat can be as high as 13000 Dollars and more. 


Hands-on: Carat, Colour, Clarity, Cut 


Imagine you want to choose a diamond for your engagement. You go to your favourite Jeweler and tell him: I am planning to give a diamond ring to my love. I saved a very long time to buy a beautiful engagement ring (or anniversary/ birthday ring). Now, my budget is 16.000 dollars. I want to get something exceptional and highly valuable for my money. Which diamond can you offer to me?
The Jeweler comes back with six diamonds. He says: They all cost the same. I ask 16.000 Dollars for each. They all have a GIA certificate, no fluorescence and a Triple Ex cut.

Which one is best for you?

  • 1.33 Carats, D, VS1
  • 1.4 Carats E, VS1
  • 1.42 Carats, F, VS1
  • 1.5 Carats G, VVS2
  • 1.5 Carats H, IF
  • 1.8 carats J, VVS2

Who didn't think at first sight the 1.8 Carat would be the best one? Now you might wonder: Which one should you choose and why? While looking at the diamonds, you start to doubt. Ok, you can see the difference in size, yes. The 1.8 Carat immediately attracts your attention. But does the slight variation in the colour matter? And will your love ever take a loupe to find that one tiny impurity which the certificate mentions and which the Jeweler says to be so-called "invisible with the naked eye" and "eye-clean"?
Does the Jeweler speak the truth when he is saying that this diamond of 1.8 Carats has the same value than the smaller one of 1.33 Carats?
The answer is, Yes, the Jeweler is right with his offer. All those diamonds- within the range mentioned in our example- trade more or less as the same value in money.The price of diamonds is daily/ weekly fixed at the diamond exchanges of the world. That means, that, in a commercial sense, none of the diamonds which the Jeweler selected for you is more precious than the other.
Is it then up to you, which Characteristics of the diamond you value most?

Please see the following information which has been written to help you make your choice. 


Does size matter? The answer might surprise you. While bigger diamonds are certainly showstoppers and will add visibly to your glamour, the average size for an engagement ring varies per city. According to a study, you needed in New York in 2019 a 1.45-carat engagement ring, while in LA, it was a 0.83- carat ring. Fashion and social expectations play a role and influence the reselling value of your diamond. The average German engagement- ring size in 2019 was 1.18 carat. Diamonds sizes, which are in the trend, sell faster and make your love happier. 

A diamond meeting investment grade criteria should have a weight of a minimum of half a carat or higher. 


Did you know that diamond graders need a special light to determine the exact colour grade? That should be either a particular lamp or the "cold" Northern daylight at noon with absolutely no ray of sunlight or colour reflections of the environment. Only by then you can tell the subtle differences!
There are many articles about diamond colours in general with a lot of information. But the variety of colours, including the lower end is overwhelming for the customer. Here is what you need to know:
The colours D- E/F fetch high prices. They are pure exceptionally white and are eligible for "investment-grade" diamonds, which means that the trade is quite sure about the future evaluation of the diamonds with this particular colour range. According to what we know by now, your D-E diamond will always be in demand, because it is so rare. Even Jewelers might have the challenge to find yours in the size you want. Of all diamonds mined, only a tiny fraction of gem-quality diamonds are of the exceptional white colour.
F as a "Rare white" colour grade is beautiful to have, too. There are not so many diamonds on the world of this shade- they appear only from time to time. But that diamond ring of your best friend might be a G-H colour. It seems to be "White". Will you see the difference?
Think about it: how often are you outside with your diamond in "Cold Northern Daylight" and have a diamond connoisseur looking at your jewel (given that there are no reflections of colourful objects in the environment)? -

Right. In all other cases, your G-H diamond will sparkle white, just as beautiful as the D- F qualities. However, it is essential if you choose this appealing colour range not to trouble the impression. Flaws in cut or too many impurities can manifold the hint of warm white. G-H Colours have the best effect with high clarity and a perfect cut, which should also secure their desirability in the future.
D- G colour diamonds are recommended to be set in white gold or platinum settings. The reflections of the tinted gold would otherwise influence the white appeal of the diamond. Notabene, this is only the case for the tiny setting around the diamond itself. The necklace, bracelet or ring body can be of Yellow or Rose Gold, too.
The colour J is at the lower end of the usual diamond colour range which Jewelers offer. But, it is Slightly Tinted White. Therefore, they trade significantly lower in price although their brightness is appreciated, too. Sometimes, you see the colour J with its somewhat visible "Warm White" combined with impressive high carat sizes. This kind of offer is desirable for diamond lovers who prefer big sizes or for those who want to set the diamond in yellow gold settings. In terms of investment, the long-term value of J- Colours is not as natural to determine as the ones of Exceptionally White- White colours. There are more insecurities concerning the future demand for this colour. However, the striking impression of a relatively big J-colour diamond might create the moment of surprise and happiness you want.

Investment grade diamonds are required to have a colour grade D-H. 



While the colour of a diamond might appear for some buyers the most apparent attribute, the clarity decides on the value, too. A flawless diamond has neither inside nor at the outer skin a flaw. An internally flawless diamond (IF) has just as little effects inside but could have minor details of polish at the outer surface. In the VVS grade (very very small inclusions), the tiny imperfections are invisible with the naked eye. It would be best if you had a 10x loupe to discover them. And an experienced diamond professional will have to look at the certificate which maps the exact location of the blemishes; otherwise, they will be challenging to find. Microscopic inclusions (VS clarity grade) can hardly become visible in the eye-sight: the stone is so-called eye-clean. In clarity grades from SI1 onwards, you can see the inclusions very often without the loupe. Also, they start to disturb the perfect brilliance of the stone because they interfere with the geometrical order of the cut. (SI2) is already a questionable clarity grade. In (I) included grade categories, the inclusions are so visible that most people will start to see them even from a distance. Therefore, diamonds with a clarity grade (I) often do not reach the shops of the jewelers. The usual range is between (IF) and (SI1). Fancy colour diamonds do not always have a clarity grading, as their colour intensity is the most desirable part of the characteristics.

Investment grade diamonds are mandatory to have a VS clarity grade or better.