Deep inside, she is anticipating that most special moment of her life when you’ll propose her to officially tie-up your destinies, offering her a diamond ring as a symbol of your commitment. 

Deep inside, you hope the moment to be unique, memorable… and that she’ll love the ring, of course! 

Very often, customers are puzzled about how to choose a diamond, and it is normal: very few people know enough about the technicalities of this field that gives the impression to be surrounded by an aura of mystery. 

On top of that, the investment can be quite substantial, so the customers needs to understand what they intend to buy. 

This article is meant to help the general public to understand the basics of gemology and to get the most beautiful and biggest diamond for their budget.


Most people have heard about the 4 Cs, which are Cut, Color, Clarity, and Carat. 

You might think right away that some of them are more important than others, and you are right! 

In my own opinion (and most gemologists will agree), the most important “C” in colorless diamonds is the Cut. 

I stress the fact that the Cut is the most important in colorless diamonds because it isn’t true for colored diamonds. 

So, you expect that stone to shine and sparkle, right? 

This is most directly related to the perfection of the cut, allowing as much light as possible not only to bounce on the surface of the facets but most importantly to get in and out of the crown (upper portion of a gemstone), resulting in a very high percentage of light return.

diamond light reflection picture

Not only excellent light return will give you a stunning piece; it will, in fact (and that is a trick to remember), make some slight flaws not as apparent as they would typically be with a lower Cut grade. 

An intense scintillation and fire in a diamond will tend to mask slightly lower grades in Color and Clarity because your eye will be too busy dealing with all the sparkles, being less prone to notice slight yellow tinges and inclusions. 

I always advise my client not to compromise on the Cut and to go for the two highest grades (Excellent or Very Good, GIA standards) to optimize their investment.


The second “C” to consider is the one that stands for Color. 

The worldwide accepted color grading ranges from “D” (totally colorless) to “Z” (very noticeable yellow tinge, just before the Fancy color grade). 

The “D-E-F” grades are considered colorless and crank up the price of stone quite significantly. 

The “G-H-I-J” grades are called near colorless and have overall the best price/quality ratio. 

The “K-L-M” grades have a noticeable yellow tinge that might detract from to beauty of the stone. 

From this level onward, I never advise my clients to buy.

diamond color grades

A little hint here to get the best out of your investment is to go for a piece that has a slight, medium or even strong level of fluorescence. 

This phenomenon occurs when a gem having a slight portion of the element boron in its structure is exposed to UV light. 

The vast majority of the diamonds showing this effect glow blue. 

Two third of the diamonds don’t exhibit fluorescence, and the ones who do are nearly undetectable under normal lighting conditions, with the only exception of extreme cases. 

The following diamonds are shown under direct UV light.

Diamond with NO fluorescence

Diamond with NO fluorescence

Diamond with faint fluorescence

Diamond with FAINT fluorescence

Diamond with medium blue fluorescence

Diamond with MEDIUM BLUE fluorescence

Diamond with strong blue fluorescence

Diamond with STRONG BLUE fluorescence

Here comes the trick: an “I” or “J” color diamond with medium fluorescence will tend to look more like “F” or a “G” one under sunlight, since the almost invisible blue glow of the fluorescence will tend to diminish the slight yellow tinge of the stone, making it look more “Colorless”. 

It’s physics.

When mixing colored light, the opposites negate each other, as opposed to creating a new color as when mixing pigments (paint).

mixing blue and yellow paint picture


You then end up paying less because your diamond isn’t perfectly colorless and less again because fluorescence is considered as a negligible flaw but still a flaw. 

In the end, your diamond will look better! 

So, unless you are a “purist,” and you’ve got the budget to afford it, the 4 Color grades of G-H-I-J will be just perfect, thus allowing you to transfer this money saved on the size of your diamond instead!


The third "C" is for Clarity. 

This refers to the "cleanness" of a gemstone regarding some potential inclusions in its structure. 

The GIA system used to classify the degrees of inclusions starts from Flawless (perfect) to I3 (Included 3). 

Inclusions can be cracks or other crystals and impurities, and the grade given to the stone by the gemology labs is to its size, frequency, and position in the gemstone. 

In the middle of the Clarity spectrum, we have three grades that I consider quite respectable since one would need a 10X loupe to be able to see any defects. 

These grades (VS1, VS2, and SI1) are considered to be eye clean, so you'll never see any inclusions in your everyday life!Here are, in the examples below, the worst cases of inclusions for each middle range of grades. 

Please take note that the specimens have been magnified eight times for the purpose of this article, so even the inclusion inside the SI1 would be almost impossible to see without any magnification.

diamond clarity grade picture

When I say “the worst cases,” I refer to the fact that: 

-The two types of cuts shown are the worst when it comes to inclusions since their long, rectangular facets make it very easy to notice defects inside the gemstone. 

-The inclusions are straight under the table (the most prominent facet, right on top of the stone), making them easily noticed. 

-They are one big black spot. Most of the time, inclusions will be scattered in a few or many small spots, and they may be grey or white instead of black. 

So, unless you are a “purist,” and you’ve got the budget to afford it, the three grades above will be just perfect, with no inclusions visible to the unaided eye and transferring this extra expense on the size of your diamond instead!

Carat (Weight)

The "C" that most people have heard of is, without any doubt, Carat. 

Carat (as opposed to karat with a "K," which is a purity grading used for gold), is a measure of weight. 

A lot of people still think that it is a unit of size, referring to the dimensions/measurement of a gemstone. 

Different shapes (round, oval, pear, princess/square, etc.) will give an impression that the gem is bigger or smaller for the same weight in Carat, because of the variation in the preeminence of the pavilion (lower part of a gem, most of the time being conic shape). 

As an example, a princess/square diamond will always seem to be smaller than a trilliant/triangle shape one of the same weight, since well-cut princess stones have a deep pavilion compared to their trilliant counterparts which are known to be quite shallow, exhibiting a bigger surface area from the top view. 

So, different shapes (even though they might be harder to find) can offer great possibilities in terms of design or weight/size appearance ratio. 

The below picture is a chart with average proportions and sizes for each respected shape for you to compare the different “face-up” appearance of each shape for the same Carat weight.

carat weight of diamond picture

You can also have a look for the "magic weights."They are ½ Ct, ¾ Ct, 90 points, 1 Ct, 1.5 Ct, 2 Ct, etc. 

"Under-sizes" are diamonds that weigh just below a magic weight; they can be a bargain, but there are a lot less to choose from. 

The most significant step in price is, without any doubt, the 1 Ct. 

One must know as well that a typical round cut diamond of 1 Ct will measure 6.5 mm diameter.On the other hand, 85 points (0.85 Ct) will measure around 6mm diameter, but you'll pay almost half the price than a 1 Ct of the same quality that will, from a distance, look pretty much like a 1 Ct!

In conclusion, many, many of my customers ended up with a bigger stone that they expected, and on top of that, their diamonds looked almost as great as perfect ones. 

I see my profession as being not only to make and sell jewels but also to educate my customers and help my customers to make the best choice possible according to their needs while respecting their budget.

Thanks for reading, and please feel free to share this article with your contacts!