In this easy guide, our goal is to make clients understand a gemstone certificate in the clearest and simple way possible.
When we are shopping for fine gemstones, either mounted in classic styles or contemporary engagement rings etcetera, certificates play a fundamental role to make an educated decision.
Among best practices, when we are looking at a certificate, we recommend to verify the authenticity of the color and clarity by double checking the diameter and the depth of the diamond with a tool called the Leverage Gauge; we always advise to get a report from the Gemological Institute of America
, as in our opinion, is the most accurate and strict of all; when on a budget always go for the best color you can afford as opposed to clarity, as the inclusions are so microscopic that it is unlikely that someone is going to notice them with the unaided eye.
For this particular article, we chose a divine D-color Internally Flawless "antique' cushion diamond which happens to be accompanied by a GIA appendix stating that the diamond is also "Type IIa".
The starting point when buying diamonds, it is always a to get a GIA diamond report of the stone we want to purchase, for the reason that, in our opinion, GIA has the most conservative grading system in the world and the most accurate one. Any other certificate would give us a good indication of what color clarity and other features are.
1. The date
It is always advisable to get the certificate as recent as possible, because sometimes the grade of the stone changes, due to wear and tear or just the handling of it. So while the always color stays the same, the clarity might change and definitely not for the better. If the certificate is older than two years, the easy solution is to ask GIA for an Update which is easy to obtain and reasonably priced.
2. The Report Number
This part is important because with that number you can double check that the values on your certificate are in fact the same as the ones GIA has in their archives. And actually, it is very convenient to do it online. In this case, we omitted part of those numbers for privacy.
3. Shape and cutting style
This section is always a source of arguments in the Trade for the reason that GIA has a terminology that it does not always distinguish the various epochs of the cutting styles, that are so important for certain dealers for a cutting style is a very good indication of the authenticity of the item and might as well very much impact the price of the gemstone itself.
We personally prefer the cutting styles that were created at the beginning of the last century for their great characters and Old World "flavor".
This is another very important piece of information for the reason that gemstone measurements help us assess quickly and easily if the gemstone we are looking at is, in fact, the same as the one described in the report.
Measurements refer to the length, the width and the depth of the gemstone.
You just need to have a gemstone gauge, which is an instrument any gemstone dealer or jewelry retailer have in their "arsenal'.
One thing to remember is that all gauges are different and we should tolerate a few tenths of a millimeter difference between the values described in the report.
5. Carat Weight
This refers to the actual weight of the gemstone. All gemstones are weighed in Carats (ct or cts), which is a unit of mass that is the equivalent of a fifth of a gram, so it is almost imperceptible to us, but might have an enormous impact on costs and values.
An easy example is a difference in price between a 1.00 carat diamond and a 0.99 carat one.
Carats are also subdivided into Points. In one carat there are 100 points (pt or pts), so the precise weight description of our 0.99 carat diamond would actually "99pts".
When buying diamonds and if possible, we prefer to avoid even number like 2.00 carats, 3.00 carats, etc. for the reason that if we would have to recut the gemstone, the loss of weight would greatly impact the price and the value of it.
As a reminder, diamonds break, chip and scratch like any other material on earth, and the only remedy is to recut the gemstone. Recutting is also performed in order to improve the stone, so its carat weight is very important: you want to consider very carefully the relation between the loss of weight and value and the improvement to its clarity and value, even when GIA indicates that the gemstone is "improvable".
6. Color Grade
This is probably the most important factor that is also the most difficult to assess with real precision, although it is perceived in broad ranges.
But no matter how much we disagree on the result of the color when we submit a diamond to GIA, it is very good to have a truly impartial final verdict on such an important parameter.
In the trade, the slightest shade of color has a huge impact on the cost of the gemstone stone with the closer to colorless (which starts with the letter "D") the more expensive.
In certain markets, colors in the range from "G" to "I" (GIA calls them Near Colorless) are very sought after and proportionally are more costly, for the reason that they look very close to the colorless range ones to the untrained eye. However, they command a much lower amount per carat.
It is curious to note that originally there was no particular reason to assign the highest color to the letter "D" other than separating this color scale from the old ones.
7. Clarity Grade
Another very important factor that affects price greatly.
Diamonds being the purest form of carbon, still have many "identifying characteristics", otherwise known as inclusions, and their absence or presence, size, number, position, nature, and color or relief determine their clarity grade.
Naturally, the freer of these characteristics one diamond is, the higher the grade and therefore the price.
Diamonds are graded with a microscope at 10x because the inclusions are invisible to the naked eye and even less to the untrained one.
In general, inclusions are visible face-up with the unaided eye only in I grade diamonds, not in any other grade. Therefore it is better to allocate a bigger portion of the budget on the color, then the clarity: nobody goes around with a loop or a microscope to check for inclusions.
Polish, according to GIA, refers to the actual condition of the diamond surface after the cutter finished the process of polishing it, or after its regular wear and tear.
Polished characteristics are related only to the external part of the diamond and are not linked to the internal one.
Diamond polish is graded on a scale consisting of excellent, very good, good, fair and poor, face up and under a 10x microscope.
In polish grades below ‘good", the luster of the diamond might be affected when viewed with the unaided eye. In certain cases, however, this might give us an indication of the epoch of the cutting style, in fact, nowadays nobody would ever think of cutting a diamond which might get a "fair" or "poor" grade from GIA.
Diamond Symmetry refers the exactness of its overall shape and the alignment, the disposition of its facets.
Like for polish, the grades for diamond symmetry are the same, and in grades below "good", the appearance of the stone can be affected without magnification.
Like for polish, grades that are "fair" or "poor" can give us a good indication of the time of the cutting style, as styles from last century were certainly less accurate and precise that current ones.
We should not rule out a charming diamond on the base of lower grade polish or symmetry as it is part of their appeal.
Fluorescence is present in about 35% of all gem-quality diamonds, and it is basically the reaction of a diamond in the presence of Ultra Violet Light, like daylight, and it causes to emit a sort of glow that might detract from its appearance
GIA grades fluorescence on a scale from None, Faint, Medium, Strong and Very Strong depending on the intensity. In intensities from Medium onward, the color of the Fluorescence will be noted in the report.
In general, the less intense the Fluorescence, the livelier is the appearance of the diamond. But there are instances where some professionals in the trade believe that blue Fluorescence can help the diamond appearance.
If you are considering buying a diamond with some degree of fluorescence, it is advisable you look at it under a different source of light, before making your final decision.
This area is self-explanatory. If there were additional information regarding the stone, they would be noted in this section
12. Report Number
This information is the same as in number 2.
13. Table proportions
The table is that flat facet that can be easily noticed looking at the stone face up, and it is also the biggest one.
In our case, it is 55% which represents the percentage of the size of the table in relation to the outline shape of the whole diamond.
We prefer a diamond with a smaller table for they have a special character typical of old European cutting styles which are so charming.
We like it also because the facets of the crown are larger allowing for a bigger visual sparkle, so for us the smaller the table, the better.
14. Girdle proportions
The girdle is that facet that goes around the diameter of the stone. It separates the top portion of the stone called Crown and the bottom part which is called the pavilion.
In high colors, the girdle is often faceted, while in lower colors it is often left unpolished.
The girdle thickness is graded on a scale consisting of Extremely thin/Very Thin, Thin, Medium, Slightly thick, Thick, Very Thick and Extremely thick.
The thickness is assessed at the narrowest sections where the upper and lower girdle facets meet.
15. Total Depth Percentage
The Depth Percentage in a diamond is the ratio between its the depth from table to the culet and its diameter.
For us is a very important piece of information, because it affects greatly the visual appearance of the stone, the lower the depth percentage, the larger the stone will appear when looking at it face up, directly through the table.
However, it is important not to go for a too extremely low percentage as the stone will have a big see through. On the opposite end, too deep stones will look much smaller than their weight and often very dark.
Our personal taste is to look for diamonds which total depth percentage is are around 45%.
16. Culet size
The culet is the facet, not always present, at the end of the pavilion, opposite of the table.
The girdle thickness is graded on a scale consisting of None, Small, Medium, Slightly large, Large, Very large, Extremely large.
In general, the size of the culet also gives us a good indication of the time of the cutting. We can assume that diamonds culets graded as none, small and medium are for sure of recent production.
17. The Plot
This diagram that in gemology is called “Plot” is very useful to identify the stone, to document its present condition and to support and explain its grade.
In our case, for example, we have an extra facet located at 12 o’clock on the crown (left) which also reaches the pavilion at 6 o’clock (right)
We should use this information to check that our diamond corresponds to the one described in the report.
We marked in red the center part of the diagram because we should always try to buy a stone that is as free of inclusion as possible in that particular area.
18. Colorless group
The finest group of colors, which are described as colorless in the report, are the ones identified as D,E,F.
In white diamonds the higher the absence of color (usually gray, yellow or brown) the more rare and expensive their cost becomes.
To the untrained eye, and in a mounting there will be no visible difference among these three colors.
It is interesting to notice that if you wash your hands wearing these colors, immediately they will look like the following tier ones. So it is advisable always not to wash your hands with these diamonds on.
It will be very easy, however, to restore their original beauty, just with a touch of steam.
19. Near Colorless Group
This is the second tier of colors where the G-H can be perceived almost as white as the colorless ones, particularly in a white metal mounting, but they are definitely not as expensive, per carat. For this reason, they are very much in demand.
In I-J subgroups, it will be possible to perceive a hint of color even if your eyes are untrained. A high polish white gold rhodium plated mounting can help raise their perception, make them appear whiter than they actually are.
20. Faint group
K colors are a great choice particularly if they have a brownish hue, in fact, they face up whiter than they are.
In this group, and in particular L to M, you will be able to perceive the impression of color even if you are not an expert.
21. Very light group
In this group the perception of color is evident.
22. Light group
This is a very tricky group because the perception of color is so evident that make us hope to get a “fancy” grade if the stone is not certified.
It is a total gamble, and you better know what you are doing, as you can lose a lot of money.
23. Flawless (FL) and Internally Flawless (IF)
Flawless diamonds show no inclusions or blemishes (which are characteristics confined to the external part of the stone) when viewed under a 10x magnification by an expert gemologist.
Internally Flawless show no inclusions but might have insignificant blemishes that can be removed by minor repolishing.
24. Very Very Slightly Included (VVS1 and VVS2)
This group of stones shows inclusions that are extremely difficult to see under 10x magnification for an expert gemologist, and only from the pavilion (the lower part of the diamonds).
25. Very Slightly Included (VS1 and VS2)
In this group of diamonds, we will find inclusion that is difficult (VS1) to somewhat easy to be found by an expert diamond grader under 10x magnification.
These inclusions will not be visible under the same magnification to anyone who is not an expert grader.
This is a very popular group of clarity grades because they are not as expensive as the previous two, they are visually very clean, but command a much lower price per carat.
26. Slightly Included (SI1 and SI2)
In this group of grades, when looked under 10x magnification, any inclusions will appear easy (SI1) to very easy (SI2) to be seen.
The untrained eye will be able to barely see them when the unmounted diamond is placed table down. Still, you will not be able to see them from the table when the diamond is mounted.
27 and 28. Imperfect ( I1, I2 and I3)
This group of diamonds contains inclusions that are obvious to a trained gemologist under 10x and are visible face up to the untrained eye.
I would not necessarily rule out this group of grades for the reason that we have to look at them in relation to all previous factors.
In fact, a diamond that has a beautiful and charming shape, reasonable color with no fluorescence and internal graining, but the clarity is in the I grade group, should definitely be considerate.
It is important to understand these grades and look at them in relation to one another, and not base your decision on just one element.
You have to look at the overall beauty and character of the stone and how it appeals to you, as nobody goes around with a loupe in her pocket and asks you to inspect your beautiful new diamond.