Last Updated on 11/04/2023 by Wit Sudjaiampun

How to Read GIA Diamond Report Like a Gemologist


Share this story

A diamond certification is a guarantee that will help you confidently make your purchase.

If you are planning to buy diamonds larger than 0.18ct, certification is important and should not be overlooked.

Diamond certifications from world-leading institutions such as GIA or HRD can be viewed as an insurance that the diamond you are receiving has the qualities you are looking for. Moreover, these certified diamonds price are usually graded under a trustable standard.

But not every diamond with certification is not an exquisite one. That is because most buyers do not have enough knowledge in reading certifications and so they slip-up and receive a diamond that is lower grade than the standard.

And so I am determined to write this article – to share this knowledge. To make you able to read certifications correctly and use it as a means of investing in diamonds in the future.

I believe that “knowledge is power”. The more you know about diamonds, the more confident you will be about purchasing them.

4 Advantages of Buying a Certificated Diamond

  • 1. Buy Diamonds Without Worries

real diamond vs fake diamond

If you are like most buyers who lack the expertise in differentiating real diamonds from fake diamonds with just your eyes; you might be at risk for buying an artificial diamond for the price of a real one or buying diamonds set at such a low price, you cannot pass up on the deal.

In today’s times, technology is moving so fast that scientists can make “laboratory-grown” artificial diamonds that are indistinguishable from real diamonds. They are known as CVD (Chemical Vapor Deposition), they look so much like real diamonds that most people cannot separate them from each other. Unlike CZ (or Russian Synthetic Diamonds), that can still easily be told if they are fake or not.

Even GIA has to open a new department to issue certifications for this specific type of diamond. In the certification, it will clearly be stated in silver grey colors as “GIA Synthetic Diamond Report” as seen in the picture below:

GIA Synthetic Diamond Report

Even so, synthetic diamonds are still not as well-received as real diamonds. They lack the natural charm of the real diamonds which goes through a process as long as billions of years. That is why synthetic diamonds’ values are greatly below the real diamonds.

When you buy a real diamond with certifications, you will immediately know the origins of your diamond. That they truly came from nature and has immense value in itself, therefore making you confidently in purchasing your diamond.

That is why certification should be a priority when making your purchase.

  • 2. You Get What You Pay For

round diamond 1 carat

If you are buying a diamond without any certifications, you are relying on your trust in the vendor. The vendor might tell you that your diamond has an E color grade, but in reality, it might have an F color grade. The price difference between those two color grades is vast, and they are impossible to tell by your naked eyes.

That is why when you buy a GIA or HRD certified diamond, there will be a clear list of details about the 4C’s of Diamonds. You can rest assured about the accuracies of these certifications because the institutions that I mentioned are two of the top institutions of the world. They have professional gemologist who grades their diamonds directly from their labs.

Checking if the certification matches your diamond or not is easy, you just have to check if the laser inscription on the edge of your diamond matches the report number on the certification.

  • 3. It Is Easier to Compare Value

diamond grading

When you have all the details on the characteristics of your diamond, you can easily compare diamond prices.

For example, if you are looking for a 1 carat diamond with E color grade and VVS Clarity and you come across two diamonds of the same price. Only that one diamond has 3 Excellent Cut whilst the other diamond only has 2 Excellent and 1 Very Good, you will immediately know that the first diamond is the better option.

At the same time, if you are purchasing a diamond without any certification – the price is indeed lower…but it may mean that you are paying more when compared to the quality of the diamond you are receiving.

  • 4. Easy Purchase, Quick Resale

2 carat oval diamond ring

For those who have purchased diamonds already, when time passes and their career moves forward to a place of stability and greater financial status, they will commonly look for a bigger and better diamond to enhance their status. That might mean selling the previous diamond as they do not wear it any longer.

In the market of second-hand diamonds, the value of the diamonds without any certification is comparable to those with certifications. The same can be said for a brand name timepiece without any receipt or insurance. That is because the person who is buying your diamond off of you would like to have reassurance as well, a certification is a guarantee of the diamond’s value.

So, if you are looking to invest in a sizable diamond, I recommend you increase your budget a bit – so that you may buy the confidence and reassurance which comes with a certified diamond. It is the more reasonable choice in the long run.

GIA Certified Diamonds Are The International Standard

There are 2 types of GIA Diamond Certifications:

  • GIA Diamond Grading Report

GIA Diamond Grading Report

A “Grading Report” is a certification that GIA commonly issues for diamonds which are 1 carat or greater. Inside the report, there will be a diagram, clearly stating the locations of its flaws. It may come with a laser inscription, but it is usually not needed as the information on the grading report is enough to see if the diamond matches.

Sometimes, you might find the opportunity to see a diamond lesser than 1 carat with a grading report. This is fairly common, only that, issuing a grading report is far more costly than a diamond dossier. That is why you will more commonly see the grading reports issued for diamonds greater than 1 carat.

  • GIA Diamond Dossier

GIA Diamond Dossier

A “Diamond Dossier” is a certification issued by GIA, it is commonly issued for diamonds less than 1 carat. The dossier does not contain any diagrams stating the flaws of the diamond but there will still be a laser inscription on the edge of the diamond, so you will still be able to check if the diamond matches the certification by yourself.

Update: Previously, in January 2023, GIA lab announced transitioning the GIA Diamond Dossier from paper reports to fully digital. However, the decision has been reverted. From April, 9th 2023 onwards, all diamonds submitted for grading with GIA will return with hardcopy paper certificates. If you already have the digital certificate, you can still access the digital report anytime from website.

How to Read a GIA Certification

Before we start, I have an interesting fact that I would like to share with you. GIA is the institution that invented the grading system of diamonds – the system is known as “4C’s of Diamonds”.

The 4C system can explain the details of a specific diamond precisely. That is why it is widely accepted in the industry. Other institutions have adopted and adapted the same principles to use for grading their diamonds as well.

That is why the “how to read diamond reports” will have many similarities. They are all based on the same principles as GIA, there are only minor differences in the terminology. I will mainly explain the GIA certifications because chances are, you will be seeing GIA diamonds more often than the other institutions.

When you have learned how to read GIA diamond reports fluently, you will also be able to read certifications from other institutions easily.

GIA Diamond Report:

GIA certificate

  • 1. Upper Section: The Name of the Institution Which Issued the Certification.

GIA cer 1

The first thing you should look for is the name of the institution which issued the certification because it greatly affects the trustworthiness in the precision of the diamond’s grading. If you buy a cheaper diamond with no certifications or certifications from a less renowned institution – it is likely that the diamond’s grading does not match reality.

For the diamond industry in Thailand, the most widely-accepted institution is GIA and HRD.

GIA or “Gemological Institute of America” is an American non-profit organization, they were established in 1931. Their goals were to create confidence for diamond buyers and sellers. Because of their strict and precise standards in grading diamonds, they became accepted as the most trustworthy institution in the business.

HRD or “Hoge Raad Voor Diamant” which means “Diamond High Council” is another organization with the same purpose as GIA. They are a Belgian organization, established in 1973. They are one of the most widely accepted institutions in Europe.

Comparison: GIA and HRD

If you want me to talk about their trustworthiness – both have exceptional reputations. The main difference as a buyer is that HRD diamonds will be securely sealed in plastic panels when they leave the lab – to reassure their buyers. Whereas GIA will send back the loose diamond in an envelope which comes with the certification.

But receiving a diamond that does not match the certification is not something you have to worry about. Both institutions will have laser inscriptions and so you will be able to check if you have received the right diamond by yourself.

Generally, GIA diamonds will have a higher value than HRD diamonds by about 5-10% as GIA is the more renowned institution and so their demand is higher.

  • 2. GIA Report Number, Shape, Cutting Style and Measurements

GIA cer 2

Report Number

The next detail you will see on the certification is the “Report Number”, it is essentially a serial number used to state the information of each diamond. You will find the same number on your diamond’s laser inscription.

Both GIA and HRD will store all their data on their website. You can check the website anytime you need to:

If you have lost your diamond report, do not worry, you can always send your diamond to the institution and have the certification reissued with some additional costs.

Shape, Cutting Style and Measurements

In the following sentences, you will find information about the shape, the cutting style, and the measurements in millimeters of diamonds.

The most popular diamond shape is the round diamond, in the certification, it will be stated as “Round Brilliant”

  • 3. The Essence: 4C’s of Diamonds

GIA cer 3

Next, the essence of a diamond is in its details – its, respectively, 4C: Carat, Color, Clarity, and Cut

diamond size chart

Carat is the weight of the diamond, it is always measured in carats (1 carat = 0.2 grams), 1 carat is equal to 100 points (same logic as 1 dollar equals 100 cents). It is common for people to refer to the weight of diamonds in points out of habit. For example, a 50 points diamond is a 0.50 carat diamond.
The carat of a diamond will directly affect the size of the diamond. The more carats, the bigger the diamond.

diamond color chart

Color is used to measure how “white” the diamond is. In truth, whiteness means a lack of color. That is because if there is color in the diamond, it will have a yellowish tint. The standard of measuring this is by the “D to Z Grading”, starting from D Color and onwards as follow:

  • D Color = 100% “White” Colorless
  • E Color = 99% “White” Colorless
  • F Color = 98% “White” Colorless
  • G Color = 97% “White” Near Colorless
  • H Color = 96% “White” Near Colorless
  • I Color = 95% “White” Near Colorless
  • J Color = 94% “White” Near Colorless
  • K Color = 93% “White” Faint Yellow

You can list the color of the diamond on downwards with the same principles of reciting ABC when you were younger. For diamonds there is no ABC, instead, it will start with D as the first alphabet and Z as the last.

And so, D Color diamonds are the whitest and most valuable whereas Z Color diamonds are the yellowest and least valuable.

But that does not mean yellow-colored diamonds are bad. If the yellow color surpasses the Z Color, the “Fancy Color Grading Scale” will be used instead. Generally, fancy color diamonds have high prices and are extremely rare.

Read more: What are ‘D Color Grade’ diamonds and are they worth buying?

diamond clarity scale

Clarity refers to the flawlessness of a diamond. Gemologists are the ones who grade clarity by using a 10x magnifier to analyze flaws, inclusions, or any other undesirable characteristics in a diamond.

Generally, the clarity level of diamond I recommend you to collect is between VVS1/2 – VS1/2 because they are fairly clean and provide a state of equilibrium between price and quality. If you go for lower qualities such as SI, you will easily see the diamond’s flaws with your naked eyes which is not something you want to be easily seen on your diamonds.

Read more: Facts you should know about IF, VVS, VS, SI clarity diamonds

GIA cut scale

Cut refers to the quality in which the diamond has been “cut”. The scale ranges from “Excellent” to “Poor”. This is 1 of 3 qualities of being a “Triple Excellent” diamond.

If you have a standard round shaped diamond with 57 facets with a certification issued after 2006 will also have “Cut Grade” clearly stated.

Many might give priority to Color, especially the D Color because everyone likes their diamond to shine white and bright. Often, you might see “white” diamonds that look cloudy and do not sparkle under the light. That is because the cut is not good enough.

Most professionals, including me, will value “Cut” the most out of the 4C’s of Diamonds because it directly affects the sparkle and brilliance of the diamond.

That is why every single diamond I choose for my clients will generally be a Triple Excellent Diamond because of their ability to shine under the light, unlike the lower grade diamonds.

Read more: What Are Triple Excellent Diamonds? Let’s Get to Know Them!

  • 4. Additional Information and Comments

GIA cer 4
Polish and Symmetry are 2 of the 3 major factors of a “3 Excellent” diamond.

Polish means smoothness of the diamond’s exterior. If the diamond has a smooth surface, it will be able to reflect light without distortion. If I were to compare it, I would compare it to shining light on to a smooth mirror – it will be able to reflect light better than a mirror with glitters of sands littered all over.

Symmetry refers to the proportions of all the facets of a diamond and how equal they appear when viewed from different angles. Diamonds with good symmetry will shine brighter than the ones with bad symmetry because of the angle light reflects on them.

diamond fluorescence

Fluorescence is the reaction that diamond shows when it is subjected to UV light.
Generally, diamonds with fluorescence will have a blue tint to them and so diamonds without fluorescence are more popular than the ones with fluorescence.
If the diamond does not have any fluorescence, it will be stated as “None” in the GIA certification whilst the HRD certification, it will be stated as “Nil”.

Read more: What is ‘diamond fluorescence’ and is it good or bad?

laser inscription

This part will tell you what has been laser inscribed onto your diamond. Usually, diamonds with certification will be inscribed “GIA” and a 10 digit number which are the same numbers as the GIA Report Number so that you may check it on a later date.

Read more: What are ‘hearts and arrows’ diamonds?


This section will be giving more details to expand on the topic of “Clarity” – what the shape of the diamond is and what flaws it has. This is a section that I do not give much importance to.

  • 5. Clarity Characteristics

GIA cer 5

Same as our fingerprints, there are no diamonds on Earth that are 100% similar. This is part of a charm that has made many fall in love with collecting diamonds.


In this part, there will be information on the different proportions of the diamond which are stated in percentages. Mainly, the information will have Table % (Width), Depth %, Angles, and Girdle Thickness.

The most important thing you should note is the “Table %” as it refers to the width of the diamond. From my experience, the Table % I recommend is between 54% – 60% (I reference this with the proportions of each case) because it is the ratio which makes the diamond symmetrical and most reflective. If it is less than this, it will seem too small and unreflective, if wider than this – the diamond will lose balance.

Other than this, you should also check the “Cutlet” which is the bottom of the diamond as “None” because having a thick diamond cutlet means that the light will not be able to pass through the diamond properly, resulting in a sub-par brilliance.

Clarity Characteristics

In the Diamond Grading Report, the locations of inclusions will be indicated on the “Clarity Plot Diagram” to help you see the special characteristics of said diamond easily.

Blemishes (external flaws) will be stated in green ink while inclusions (internal flaws) will be stated in red ink.

Read more: Clarity characteristics: tips only known by experts

Good VVS/VS: Things You Should Not Look Over

Generally, diamonds that are not IF (internally flawless) will have flaws. The number of flaws will depend on Clarity. For example, VVS diamonds will have fewer flaws than VS and SI respectively.

But that does not mean VVS or VS diamonds will have the same flaws in the same locations because often, you would see VVS or VS diamonds will have flaws on its table which is highly undesirable.

Great diamonds should not have their flaws on their table. Instead, the flaws should be located elsewhere so that they are easily camouflaged by the casing. In the industry, we call these diamonds Good VVS or Good VS.

Personally, every single diamond will have to go through me before they are given to our customers. I will select only Good VVS and Good VS diamonds even though in a hundred diamonds only one or two may possess these qualities. It is a tedious task, but I wholeheartedly do it to ensure that my customers will receive the most beautiful and brilliant diamond possible.

  • 6. Security Marks

GIA cer 6

Lastly, you should look for a seal of the institution (Security Marks) to ensure that you are holding a real certificate.

For GIA, their certifications are sealed by a golden logo with slight protrusions. Their seals are unique and difficult to replicate, once you have seen their certification – you can easily tell if it is real.

Conclusion: Diamond Reports Are a Guarantee That You Will Able to Make Your Purchase With Confidence

At this point, you probably know the advantages of buying a certified diamond. And also the different types of diamond certifications and how to analyze each section in detail.

So, the next time you have an opportunity to buy a diamond, you will know that just looking for a D Color graded diamond or a 3 Excellent diamond is not enough if you wish to own a truly brilliant diamond jewel.

Because in reality, many other factors will contribute directly to the value and beauty of the diamond you are considering. These factors may include fluorescence, Good VVS/VS, Table, Depth, Cutlet, Girdle, and et cetera. Which may seem like a minor detail which other vendors look over, giving it less importance than it deserves.

But every single diamond gem you receive from me will be of the first-class standards of the diamond industry which I always offer from the heart.
If you have any other questions on reading a diamond report, you can contact us now.

Need help completing your order?

Get in touch with one of our diamond specialists.

This website use cookies to enhance your experience and providing the best service from us. You can learn more about our use of cookies in Privacy Policy

Privacy Preferences

Manage your cookies preferences.

Accept All
Manage Consent Preferences
  • คุกกี้ที่จำเป็น
    Always Active

    ประเภทของคุกกี้มีความจำเป็นสำหรับการทำงานของเว็บไซต์ เพื่อให้คุณสามารถใช้ได้อย่างเป็นปกติ และเข้าชมเว็บไซต์ คุณไม่สามารถปิดการทำงานของคุกกี้นี้ในระบบเว็บไซต์ของเราได้