Diamonds 101

Diamond Certification & Grading | 4C's Education | Rare Carat

Diamond Grading Laboratories

So here’s the lowdown - for natural diamonds, we recommend GIA certificates. It’s the gold standard in the industry, and many other labs are often known to ‘overgrade’.

For lab-grown diamonds, we recommend IGI and GCAL certified diamonds.

The Language of Diamonds

That ‘language’ is the grading system. Its purpose is to communicate to you in the clearest possible terms, the quality of the stone you might be looking to buy, and it does so by assigning certain ‘grades’ to a particular stone. These grades (based on our 4C’s, which we now know lots about) are usually assigned to each stone in places called ‘diamond grading laboratories’, which are full of trained gemologists who sit hour after hour, day after day, examining diamonds in very controlled environments.

loupe and ring .jpeg

At the end of this arduous process, they produce a report, which states their opinion regarding the quality of the stone in question. Simple!

Now I’ve got some good news and some bad news for you, and I’ll start with the bad news because apparently, that’s the way you are supposed to do these things. The bad news is that this diamond grading system is pretty darn complicated, and is based on rules that can change from one place to the other (like dating, but not nearly as fun).

The good news is that I am here to offer you some guidance through this labyrinth of information, in the hopes that it will make your journey a little easier. If you think about it really, really hard, I’m kind of like Wonder Woman saving you from evil - but instead of evil it’s just pages and pages of boring diamond grading information.

History of Diamond Grading

First, some history. This diamond grading system we have come to know and love, was created in 1931 by an American wholesaler named Robert M. Shipley, who travelled around the USA selling diamonds to retail jewellers across the country. During his long trips (trying to sell diamonds to every Tom, Dick and Henrietta he came across), Shipley realised that not only were his customers completely clueless about the diamonds they were selling, but the way diamonds were graded varied wildly from place to place.

Dealers and retailers in the industry would simply make up ways to rank diamonds, often using different lettering such as ‘A/AA/AAA’, or words like ‘super/super plus/super plus-plus’ as a way to identify the quality of different diamonds. In short, it was a hot mess.

Shipley believed that a universally accepted ranking system would eliminate the confusion about the quality of diamonds, which would sell more diamonds, which in turn would make everyone rich, fat and happy. Yay Richard! With this in mind, he established the Gemological Institute of America (GIA), which in the beginning, was only a place of education where jewellers could get certified in gemology.

These jewellers were going back to their respective stores with vast amounts of knowledge about diamonds, but more importantly with the skills to rank diamonds according to the grading system that the GIA had taught them. They were slaying it. However, pretty soon the number of jewellers wanting to be certified was more than they could accommodate, and so the GIA began allowing these jewellers to simply send the stones they wanted graded (for a fee obviously), making life easier for everyone. And with that, the modern diamond grading business began.

Hurrah, you finished the history section! Here’s a picture of a “I Love History” badge. Feel free to print it off and pin it to your t-shirt. Or not.


Different Grading Labs

Now that we are all wearing our badges (*cough*), let’s have a brief look at the main laboratories in the diamond grading business today. We’ll start with the GIA, partly because it is the most well-known of all the labs, but also because all other labs are compared to the GIA in terms of reputation and standards.

The Gemological Institute of America (GIA)

GIA sign on campus.jpg

As we learned above, the GIA was the first grading laboratory to come up with a detailed process of diamond evaluation. Indeed, during its first few years in operation, the growing clout of the GIA helped to demystify the entire diamond business, as it brought much needed information to customers and retailers.

In today’s world, little has changed. The GIA’s powerful market position stems from this long-standing reputation of being the industry benchmark, a reputation that is being constantly reaffirmed every time a dealer trades a GIA stone, or you purchase one! Gemologists from different labs admit that it is difficult to compete with the GIA in the market, simply due to their long running respectability as the market leaders. In fact, I spoke to one gemologist who explained why it’s so difficult;

“The problem is that although our lab and GIA are seen to have the same standards, our lab is still actually valued lower in the industry. That’s just how it is, and it’s the way the industry operates. And it’s hard because people say, well, why would I get my stone graded with you if I can get it graded at the GIA and sell it for more? They know the GIA grading report has a higher market value. What can we say? All we can do is try to come up with different ways of attracting customers to us instead.”

As you can see, trying to compete with the GIA can be a frustrating affair. It’s like trying to convince someone to go out with you, when George Clooney/Megan Fox have already asked for a date. Sorry to burst your proverbial bubble, but you haven’t got a chance, mate.

American Gem Society (AGS) Grading Lab

Indeed, few have risen to the Clooney/Fox reputation stakes in the diamond grading world, with AGS being a notable exception. The AGS has a stellar reputation, and is known for its strict grading standards as well as its ground-breaking work in the area of diamond cut quality analysis.

If you have been reading my previous articles, you will know that ‘cut’ is the most crucial of the 4C’s. The AGS caught on to this early in the game, and created a new and innovative performance cut grading system that essentially revolutionised cut grading. Although they have slightly different grading terminologies (more on this in part two of this series), they continue to provide an excellent alternative to GIA in the diamond grading world.

HRD Grading Lab

Now that we have looked at the top players, let’s take a peek at those whose reputations are not as sturdy. First, we shall look at HRD. Now, far be it for me to tell you what to do, but it is my opinion, that HRD grading certificates are not the most reliable of the bunch (they are not the worst, however).

Take a look at this table and you might understand why;

Stock Num. Test 7
Shape Round
Weight 1.06 carats
Measurements 6.54*6.44*4
None None None None None

This is one result of an [experiement]( conducted by Rapnet (an online polished diamond trading network), during which they sent 10 diamonds of varying sizes and qualities to 6 different laboratories in order to ascertain the difference in standards (if any) between the way each lab graded each stone.

As you can see, the difference between the grades given by the GIA and the HRD are clear. While it is true that a variation of one grade, either way, is not a huge deal, these all add up. On paper, the HRD diamond might look great, but in reality, you are paying for a lesser quality stone. An HRD graded diamond may be cheaper, because most in the industry know that they wiggle around with the grading ranges (one or two color grades up here, two or three clarity grades up there) and so they are priced accordingly in the marketplace.

That said, if you are less worried about what the report says, and more interested in how the diamond looks in real life, then it might be a good way for you to save some money - as long as you see the stone first. I cannot stress that enough.

European Grading Laboratory (EGL)

Now let’s talk about EGL. Poor EGL, how the mighty have fallen! They are like the super popular kid in high school that everyone looked up to, who ended up living in their car behind Walmart. Once a titan of the diamond grading world, they have been plagued with controversies over the last few years. You see, the EGL (once one big organization), splintered into many different franchises – all with wildly different standards and therefore reputations.

EGL USA is deemed the most reputable. But you need to be very careful when you are looking at a diamond whose certificate is labelled ‘EGL’, that it is fact ‘EGL USA’ and not ‘EGL Hong Kong’, ‘EGL Israel’, ‘EGL Europe’ of any other EGL for that matter.

If you are not sure, email or call the retailer and get a full copy of the grading report (retailers at Rare Carat only have GIA graded diamonds listed). Just like HRD, EGL diamonds (even EGL USA) will sell for lower prices than GIA certified diamonds (15-20% or more), and just like HRD, that difference in price represents a difference in standards.

To give you a bit of industry context here, Rapnet (the online diamond trading network, and a big deal in the industry) was so concerned with the misrepresentation of quality associated with ‘certain labs’ using the GIA terminology – but crucially – applying this terminology to different grading standards (read, looser standards), they decided in 2014 that they would no longer list any EGL grading reports on their website. Read from that what you will, ladies and gentlemen....


International Gemological Institute Grading Lab (IGI)

IGI is the most popular grading lab for lab grown diamonds. Yep, you read that right! The GIA did not issue a comprehensive grading report for lab grown diamonds (LGD for short) until very recently (like October 2020 recent). The IGI took note of this, saw a huge opportunity and ran with it. Smart move for the IGI.

Lab grown diamonds are graded on the same scale as natural diamonds and the grading reports contain the same pertinent information like cut, color, clarity, carat weight and proportions.

As for natural diamonds graded by the IGI, stick with GIA or AGS. The IGI is good, don't get me wrong, but the other two heavy hitters are better and carry more clout.

Almost done

Of course, some labs have decided to look at it as an opportunity rather than a hindrance. Instead of trying to imitate the GIA standards, they actively move away from them in order to carve out a little niche in the market for themselves. They come up with strategies; faster turnaround time, discounts on larger parcels of diamonds, and even grading to a different standard. They might gain a reputation as a lab that grades a little sweeter, which can attract the attention of those smaller, struggling dealers and retailers who need to squeeze as much juice from the profit as they can in order to stay afloat. After all, if you are a small dealer and you know that the GIA will grade your diamond as a ‘G VS2’ but another lab will give it an ‘F VVS2’, which one might you go to? That could mean a difference of hundreds of dollars, which is no small change when you are a small fish in a very big pond.


WELL DONE! You have reached the end of a very long, but highly informative article on grading laboratories! Who would have thought the diamond world could be so interesting? Now, see you all again in Diamond Grading Reports, where we will take a closer look at what a grading report is, and just as importantly, what it is not...

Diamond Grading Reports

Welcome to Part Two. I’m thrilled you are here. Now as you’ll remember, firstly we examined the different laboratories you might come across on Rare Carat. Now, I want to go into a little more detail on what these reports actually are, and just as importantly, what they are not.

The basics

OK, let’s start with the basics - what is a diamond grading report? A diamond grading report is a document that offers the buyer (that’s you, hi!) a gemologist’s evaluation of the quality of a diamond. These gemologists will likely be located at one of the laboratories we learned about in the previous post – a vast majority of them at GIA.

“In short, a diamond report can tell you a good deal of information regarding the quality of the diamond you are looking to buy.”

This report will contain detailed information such as the measurements of the specific stone, its weight, its color and clarity, as well as an outline (either in a plotted diagram or some other feature) of any other particulars you might need to know about.

These particulars could be in reference to the location of any inclusions or imperfections, or if the stone has undergone any treatments (like laser drilling). In short, a diamond report can tell you a good deal of information regarding the quality of the diamond you are looking to buy. Not quite what it had for breakfast, because that’s not a thing, but a decent amount nonetheless. Now, because I’m pretty confident that many of you will never have seen a report before today (because you were busy living your lives), here is an example so you know what to expect;

GIA Certification

This is an example of a GIA Diamond Grading Report. This is also known as a ‘full’ report because, in addition to a diamond’s 4C's information that you can see on the left, it also provides a plotted diagram of the stone’s clarity characteristics and a graphic representation of its proportions. This is a nice feature, as you can get some insight into where exactly those pesky inclusions are rather than just having to rely on the clarity grade alone. Something to keep in mind while you're searching: a plot diagram is only included on grading reports for a 1 carat or higher diamond.

The Date of Issue

I want you to go back and look at the sample report again though, this time focusing on the top left-hand box. There you will find two important features that I want to touch on briefly; the date of issue, and the GIA report number. Let’s start with the date.

The date of issue is important as it gives you some insight as to whether you have an ‘old GIA’ report or a ‘new GIA’ report. Now, there is nothing wrong with having an old GIA report, the only thing to be cognisant of is that the GIA changed their grading procedures around 2006, specifically in relation to cut grades (pre-2006 the reports didn’t even include cut grade). Here’s an example of one from back in the day;

GIA GEM Trade Laboratory

See? no cut grade! MIND BLOWN. But how might this affect you? Well, it could mean you get a good deal on a great quality stone. It could also mean that the diamond in question has not been re-graded because the seller knows it will not receive an ‘excellent’ cut grade. This in turn could mean that you’re paying top dollar for a GIA graded diamond, without the full bells and whistles of the modern report (i.e. a cut grade, which we know is super important). Boo!

The second reason the date of the report might be important is in relation to any imperfections. If you come across a report that is 10 years old for example, you need to be aware that any chips, scratches or bruises on the diamond will not be reflected in the clarity grade on the report.

Some girl may have thrown the ring at her fiancé in a fit of jealous rage, chipping it on the granite countertop in the process. Life happens, you know? Because of these facts, and because a diamond is a very big purchase, I would recommend asking for the diamond to be re-graded if you happen to come across one with an old report. This way you can be sure you’re getting what you pay for.

If you are looking to make sure your diamond has never been worn by another person however, a ‘new’ GIA report will not help you. It could very well be the case that an old stone has just recently been regraded. Do not fret – diamonds are hard wearing, and if the grade on the report says it’s a triple excellent, I would trust that it is.

After all, getting a diamond graded at the GIA costs about $100, so if a retailer is trying to sell you a stone with an old GIA report, is it really because he wants to save the cash, or something else? Hmm? Hmmmm???


Suspicious cat again...

The Report Number

Moving on, let’s quickly touch on that report number. The report number is important because it provides you with a nifty security feature, meaning you can always go and check with the GIA here to make sure that the report is real and valid. In fact, if you are buying a stone under 1ct from the GIA, most likely you will get a Diamond Dossier instead of a full report anyway.

Fear not!! This is not a lesser quality report. It is merely a more compact version of the full report. The only difference is, that instead of having a plotted diagram of the clarity characteristics of the diamond, it has a super awesome laser inscription of the diamond’s report number on the stone’s girdle. That way you will be 100% sure that the diamond in your hand is the same as the one that the report reflects. Plus, let’s face it - everyone loves lasers.

An AGS Report

Finally, just for comparison let’s look at an AGS report;

American GEM Society Laboratories

I wanted to show you an AGS report in particular because there are two distinct features here that are worth pointing out. First of all, as you can see right down at the bottom of the report, they have a different ‘language’ for how they grade diamonds. For example, instead of the diamond being a GIA ‘H’ color, it is an AGS ‘2.0’. This is totally fine, and just needs a bit of getting used to.

The second (and really cool) feature of the AGS report, is that they give you an ASET image (those two colourful images near the bottom of the report). An ASET image offers an indication as to how well the diamond is making use of the light around it. Although I would not encourage you to base your purchasing decision on this alone, I do think it is a really great tool to help you determine how sparkly and brilliant that rock is actually going to be. It is also a very clever way for AGS to distinguish itself from GIA, by offering an additional feature. Well done AGS! If you want to know more about how to read an ASET image, click here.

What a Diamond Report is NOT

First, it's not a certificate

Now that we have an understanding of what the grading report is, I want to spend a little time discussing what it is not. First of all, it is not a certification. I know the section is called Certification, but we do that because that’s how it is referred to in the industry.

I’m going to get a bit pedantic for a second, but it’s important, so bear with me. Many people (including us) inaccurately refer to the piece of paper that accompanies a diamond as a ‘certificate’. But we want you to know that the word is not used appropriately here because a ‘certificate’ suggests a statement of fact.

In truth, a diamond ‘report’ is nothing more than a statement of opinion. Granted, the opinion of a well-trained gemologist, but an opinion nonetheless. And as we have seen, these ‘opinions’ can vary depending on who is doing the evaluation (we’re looking at you, EGL).

If you are in a store and a sales assistant tells you that the diamond you are looking at is ‘certified’, ask them to clarify. Often, they are just confusing the two terms and really just mean that it has a report. However, it could also mean that they are trying to sell you a diamond that has some form of in-house certificate.

Some fancy branded diamond stores who I will not name (*COUGH, Tiffany*), do have their own diamond grading systems that are known to be very robust. Just make sure you check before you buy!!

Anyone trying to convince you that their own in-house certificate is of GIA standards, is playin’ you for a fool, Son! Just because their jeweller happened to graduate from the GIA gemology school, does not mean that the ‘certificate’ is of GIA standards. From now on, any time you hear ‘in-house certification’ I want you to think of this...

Snow White

Second, it's not a statement of value (aka an appraisal)

Moving on. The next thing that a diamond grading report is not, is a statement of value. A diamond report should never, ever indicate a monetary value associated with that diamond. See how I put the word ‘ever’ in bold? That means I’m serious. A monetary valuation is the job of an appraisal, which you can (and should) get in addition to a report.

The appraisal will assign a monetary value to the diamond, based on current market conditions as well as the quality of the diamond. These appraisals are usually prepared for insurance purposes, and because of this, the value will often be far higher than the actual price tag on the ring. This is actually a well-used sales tool, designed to make customers believe they are getting a great deal. Don’t fall for this. If someone tries to sell you a diamond using only an appraisal, think of this;

Snow White

Of course, buying online with Rare Carat avoids many of these nasty tricks. #shamelessplug

Finally, it's not an indication of the stone's beauty

Finally - and perhaps most importantly - a diamond grading report is not an indication of the beauty of the stone. I cannot stress this enough, people. Use the grading reports as a tool to help you, but do not let them be the final answer.

The absolute best way for you to know if a diamond is right for you, is to get to know it. Get a feel for its personality. Really examine it, look at the video, compare it with your other favorites and talk to a gemologist about it. And if the grading report says the color is not so awesome, but when you see it you absolutely fall in love with it…grab that diamond and run like the wind!

Pay for it first though, obviously.


How do I get my diamond certified?

In order to get a diamond certified by an independent lab like GIA, you would need to reach out to them first and create an account. Your diamond has to be loose, which means not set in any jewelry. Lets take GIA as an example. They do not offer grading accounts to the general public, so you'll need to go through your jeweler. Your jeweler will have to have a grading account with them and will send the loose diamond to GIA. Grading times vary based on how busy the lab is and what services you are asking for. Once completed, they will assign your diamond with a GIA report number that you can look up using their report check feature online at Then your diamond and your GIA documents will be mailed back to you.

Is a diamond certification important?

Yes! Very important these days. This is an independent opinion on the grade of the diamond. Otherwise, you are buying a stone based on just the jeweler's word and expertise. Having a GIA certified diamond will raise the value of the stone as well as peace of mind of knowing exactly what you are buying. Besides that, a certification gives you much more detailed information that a standard jeweler will not be able to tell you, like the cut grade, proportions, and types of inclusions. These are all very important details!

How much does it cost to have a diamond certified?

The pricing to grade a diamond by GIA depends on the carat weight. The starting price is $48 for .15cts to .22cts and goes up slightly for each carat weight. A 1.00ct diamond costs $110. Keep in mind that getting a diamond laser inscribed on the girdle is extra as well as any rush on the report. There is also an option for an origin report which starts at $75 for the smallest carat weight (not all diamonds can receive origin reports). You can find a full list of prices on

Are GIA certified diamonds better?

Having a GIA certified diamond doesn't make the diamond better, however GIA certified diamonds will cost more. This is because it is given an educated opinion by a GIA gemologist as opposed to a biased opinion by a jeweler that is trying to sell you the diamond. GIA is the standard in the industry for diamond grading and most consumers look for this documentation when buying.

Should I buy a diamond that is not certified?

You can buy a diamond without a certification however we recommend not doing that unless its an antique stone (as these were not certified back then). With no certification, you are relying on the information that is given to you to be true. Not knowing the education of the person that is telling you, or whether their opinion is accurate. Having an independent laboratory grade the diamond for you is more peace of mind.

Should I buy an EGL certified diamond?

I recommend investing in only GIA or AGS certified natural diamonds (or IGI, GIA or GCAL for lab grown). They hire only the best gemologists to work in the labs and grade diamonds, therefore they are much more accurate with the grades that they give. There are a lot of other laboratories out there, however they are all known for being much more lenient with the grading. They appear to be less expensive when comparing, however the report is not as accurate in the color and clarity grading. This is why they will sell for less money.

What is GIA?

GIA is an independent laboratory that grades diamonds and gemstones. They have a team of gemologists that are highly educated that grade the stones. When grading a stone, multiple gemologists have to look at the stone and agree on the grades before finalizing the document. This ensures that it is the most accurate. They are located in New York City as well as Carlsbad, California (they also have labs in other countries, for a full list visit their website at GIA is also the leading school for education on diamonds and gemstones as well as jewelry and the industry.
Dr. Rian Mulcahy
Dr. Rian Mulcahy
Rian is officially a Diamond PhD - just ping us if you’d like to read her fascinating 200-page thesis, titled Facets of Value: An Investigation into the Formation of Worth in the Diamond Market. She has consulted various firms all along the pipeline, from the rough diamond market to the recycled diamond industry. She holds an MA in Globalisation and Development from University College Cork and a PhD in the Sociology of Diamond Valuation from the London School of Economics.