For most men diamonds are an unknown territory! Sure, you can teach yourself everything you need to know about diamonds and thus measure the quality of a diamond with your own eyes. And indeed, if you get yourself properly educated you will become pretty good at estimating the 4C parameters of a diamond. However, even diamond experts would have difficulty in estimating the exact color of a diamond for instance. That is why it is important to only choose a diamond graded by one of the best diamond grading labs.
This way you will have an accurate and objective report of your diamond parameters. And this in turn will enable you to estimate the market value of your diamond way more precisely.
However, there are many different grading labs out there. Many of them apply different grading criteria so that it really is not easy to know what to look out for in a good grading lab.
Which diamond grading labs are the best in general?
The biggest and most well-known grading labs are GIA, AGS, EGL and IGI. These are also the ones that you will most likely stumble upon when buying a diamond.
In my own experience I know that both EGL and IGI have very low grading criteria in color and clarity. This means that when you have the very same diamond graded by IGI/EGL and GIA/AGS it invariably will always be the case that both the clarity and color grades given by IGI/EGL will be 2 or even 3 grades higher.
This means that for instance a diamond that would be graded a SI1 in clarity and H in color by GIA/AGS, could be graded VS1 in clarity and F in color. Such a diamond would be worth much more on the IGI/EGL grading report because seemingly the color and clarity grades are better than what GIA/AGS would rate for exactly the same diamond.
For this reason many jewelry stores try to sell diamonds with IGI/EGL grading reports to their customers. Prices of white diamonds are quite transparent and are dependent on all the diamond’s 4C parameters. Obviously, if you have a diamond that is graded better on an IGI/EGL lab report you can also demand more money from your customers!
For this specific reason I would recommend everyone to avoid IGI or EGL grading reports! It will definitely be more beneficial for you to stick with GIA or AGS grading reports! You can be pretty sure in this case that your diamond will be graded pretty accurately.
Many jewelry stores will even tell you that a GIA or AGS grading report is more expensive and it is for this reason that the diamond is only graded by IGI or EGL. The truth hower is that jewelry store oweners know perfectly well that a diamond graded by GIA or AGS will have lower color and clarity grades because GIA and AGS are stricter. Which means that the store cannot charge as much money for the diamond.
In fact, when I first went out to look for diamonds in brick and mortar stores, I was told that there is no need for GIA and AGS grading reports because they are more expensive and will also make the diamond more expensive! In fact, the opposite is true!
If a jewelry store is not willing to offer you any GIA or AGS graded diamonds you simply have to walk out of the door! And the same applies to online stores.
By the way James Allen only offers GIA or AGS graded diamonds so that you don’t have to worry about inaccurate grading reports.
What about in-house reports?
Just forget about in-house reports! In-house reports are grading reports issued by the company you are buying from. Such a company could grade their diamond whatever they want. I think that I don’t have to explain to you why it might not be wise to trust such an inhouse report.
However, an in-house report can be a nice extra if it accompanies a GIA/AGS grading report. In such a case the diamond will already be graded by a reputable grading lab and the in-house report can serve the purpose of making the best decision between several options.
Which grading lab to choose?
As I have told you, GIA ad AGS are the two most reliable grading labs with the overall strictest grading criteria. This ensures that you will not overpay on the diamond.
Further differentiating between GIA and AGS the following might be said: In general AGS is somewhat stricter in cut and GIA has stricter criteria for clarity and color grades!
In clarity and color it is generally accepted that there is a margin of error of around one grade. For this reason the same grading lab might even give you another color grade when grading the diamond at a later point in time.
In my experience the same diamond graded by both GIA and AGS is more likely to receive a better color and clarity grade by AGS. However, this need not always be the case.
To go for the really best grading lab I would go for GIA because they tend to be stricter in color and clarity. It is exactly these two parameters that will be the most difficult for you to figure out on your own! The cut on the other hand is easier to figure out on your own if you take a close look at the diamond proportions.
Now, the cut parameters are somewhat tighter for an AGS graded diamond to be graded an AGS0 (Ideal) than for a GIA graded diamond to be graded Excellent. However, both grading labs measure the same cut parameters ( and they do it with the around the same accuracy. For this reason I would choose a GIA graded diamond and then simply have a look at the diamond’s cut proportions. As stated in my post about round cut diamonds these should be within the following proportions for round cut diamonds:
Of course, if you don’t have any other choice it is also absolutely okay to go for a AGS graded diamond, too.
As long as you don't accept any EGL and IGI graded diamonds you will be doing fine!