Understanding the basics of diamond grading will enhance your buying experience and insure that you select a diamond that best fits your needs.
The good news is that you don’t have to take a course or read several books to gain this knowledge; that is our job. Our guide will help you put things in perspective and focus on what is most important to you.
The “Four C’s” refer to: Color, Clarity, Cut and Carat. It is the combination of these four factors that determines a diamond’s performance and beauty.
Almost all diamonds possess some degree of body color, usually yellow or brown. A small percentage of diamonds are colorless, and an even smaller number possess body color so strong that they are classified as “fancy colors”.
Color is graded on the scale developed by the GIA and is almost universally used today to classify diamonds in the world market. The normal range of this alphabetic scale starts at D (colorless) and runs through Z (light yellow or brown). Colorless stones are rarer and more valuable than stones with body color in the normal range. However, diamonds graded as fancy are analyzed differently and can be extremely valuable.
It is helpful to think of the scale in terms of grade ranges: D,E,F are considered colorless, G,H,I,J are near-colorless and lower grades are slightly tinted to lightly tinted.
Differences between color grades are extremely subtle. Professional diamond grading is done in controlled lighting conditions with the stones in table-down position, with the grader looking through the girdle of the stone in order to see the slight differences in body color. Diamonds in the near-colorless to colorless range will appear white or colorless to the eye when viewed through the table.
In addition to the increased rarity and value of colorless stones, body color also impacts the quality of light emanating from a diamond. Body color acts as a sort of filter that diminishes to an extent the pure nature of light returning to the eye. Colorless diamonds that are well-cut exhibit the best spectral display or fire.
Although lower colors can still be very beautiful Gem Diamond Company prefers to sell only diamonds of J color and above.
Fluorescence
Fluorescence, also known as photoluminescence, is a property in some diamonds that causes them to glow when exposed to ultraviolet light. The effect is rarely noticeable under normal circumstances and is chiefly an identifying characteristic of a given diamond. In many cases fluorescence is a benefit, helping lower colors to appear whiter, but in rare cases it is detrimental, causing the stone to look slightly foggy in certain light.
Our Advice:
While colorless stones are rarer and cost more, near-colorless stones will look essentially the same to the eye when set in jewelry. Choosing a GHIJ color instead of one in the DEF range will enable you to get a larger diamond for the money, without a substantial compromise in performance or beauty. If the diamond is to be set in white gold or platinum, aim a little higher on the scale than you would if setting it in yellow gold. Yellow gold disguises body color whereas white metal reveals it.
Blue fluorescence can add to eye appeal of near-colorless diamonds and therefore be a benefit. Very strong fluorescence will not enhance colorless stones and may detract from their beauty and value.
Clarity
Nearly every diamond contains some external blemishes or internal inclusions that can be detected with magnification. To the extent that diamonds are free of these characteristics they are more rare and valuable. Diamonds with higher clarity or purity are more expensive than diamonds with lower clarity and more imperfections. In addition to being rarer, stones with higher clarity are capable of reflecting and refracting light better.
Diamonds are graded for clarity based upon the number, size and location of these tiny inclusions. They also serve to create a very unique identifying signature for a specific diamond, much like a fingerprint. The clarity grading system most widely used around the world is the GIA scale. Professional grading is done in controlled conditions under 10X magnification.
It is helpful to think of clarity in terms of grade ranges with the following descriptions:
Our Advice:
For jewelry purposes Si2 clarity is sufficient to allow for brilliance and performance. Even close examination with the naked eye will not reveal any flaws in most cases. For engagement purposes many buyers prefer stones with higher purity. Selecting Si1 or 2 rather than a higher grade can enable a buyer to own a larger and/or better color diamond for the money without a substantial drop off in beauty or performance.
This is the easiest factor to understand, although there is a little wrinkle here too! Carat is a measure of weight: 5 carats = 1 gram, 1carat = 0.20 gram.
Carat weight is stated decimal terms, such that one carat is written 1.00ct. One and a half carat = 1.50ct, three quarters of a carat = 0.75ct and so on.
Diamonds less than one carat are commonly talked about in terms of points which are simply percentage points of a carat (1.00ct= 100 points). So a quarter of a carat (0.25ct) is said to be 25 points, half carat is 50 points, 0.98ct is 98 points and so on. Because a carat is a unit of weight, diamonds of exactly the same carat weight can appear to be different sizes, depending on the proportions of the cut. A thicker or deeper cut will look smaller than a stone with a larger surface area or “spread”.
The illustration below shows relative visual sizes of well cut diamonds in a range of carat weights. (not intended to represent actual sizes)
Rarity and value increase with diamond size- an important concept to appreciate. A 1.00ct diamond of a certain quality is far rarer than the same quality in a 0.50ct diamond. Therefore, the cost of the 1.00 is more than simply twice the cost of the 50 pointer. As a result, the per carat price of like quality diamonds increases with size. In the example above, the 50 pointer might cost $2000/ct -a total of $1000, whereas the 1.00ct diamond in the same quality might cost $3900/ct totaling $3900.
Note: Carat is sometimes confused with Karat (and for good reason!). Whereas carat is a measure of gemstone weight, Karat is a measure of gold purity. 24 Karat is pure gold, 14K is 14/24 pure (58.5%), 18K is 18/24 pure (75%).
Our Advice:
Apparent diamond size varies depending on the carat weight and the proportioning of the cut. A 1.00ct stone that is cut a little too deep might actually be smaller looking than a 0.90ct stone that is well proportioned. Also, at certain carat levels, per carat prices increase substantially. It is sometimes possible to get real price savings by staying just under these so called magic marks. For instance, a well cut stone of 0.45 ct might be quite a bit less expensive than the same quality 0.50ct, yet have a visual appearance virtually the same. The important magic marks are 0.50ct, 0.70ct, 1.00ct, 1.25ct, 1.50ct, 2.00ct, 3.00ct, 5.00ct.
Cut is the only diamond value factor that is the result of human input. This important factor may be the most difficult to understand because it is the most technical, but gaining a basic understanding does not have to be daunting. Cut refers to the proportioning, alignment and finish of a diamond’s polished faces or facets. Proper cutting enables a diamond to perform at its best and release its full potential for fire and brilliance. A well cut diamond will be more beautiful and more valuable than a poorly cut stone.
In addition, a cutter will usually have to sacrifice more of the rough stone to produce a well cut finished stone, thereby ending up with a smaller diamond than had he taken liberties with the cut. Well cut stones therefore yield less weight from the rough and are therefore more expensive to produce.
Fire, Brilliance, Scintillation
These are the three aspects of diamond performance and they are distinct elements.
Fire refers to a diamond’s ability to act as a prism and to break white light into its spectral colors. Diamonds with good fire will exhibit little sparks of red, green, yellow and blue as light refracts through and out of the stone to the eye.
Brilliance is the total amount of light returned to the eye and results in the overall brightness of the stone.
Scintillation is the sparkle of the diamond and is determined by the cutting style and execution of the cut.
The quality of a diamond’s cut is a complicated interaction of proportions and finishing factors. Many combinations can result in beautiful finished stones. Because the above mentioned performance elements are distinct, it is possible for the cutter to make tradeoffs in the process. For instance, making the table facet a little larger may make the stone slightly more brilliant and slightly less fiery. So while there are cut guidelines, in the end beauty is in the eye of the beholder.
Note: The word cut is also used in reference to a diamond’s shape — round cut, marquise cut, princess cut, etc. It is less confusing to restrict the term cut to a discussion of the proportions, alignment and finish of a polished diamond.
The following illustrations show the various parts of a diamond and the measurements used in the analysis of a diamond’s cut:
Diamond Anatomy
Table, Depth, Polish and Symmetry
Depth percentage, the ratio of the total depth to the diameter, and table percentage, the ratio of the size of the large table facet to the diameter of the stone, are the most important factors affecting the overall performance of the diamond.
Additionally, two other factors in the detailing of the diamond are important in fine tuning the final product. Symmetry refers to the alignment of the facets with one another, and polish refers to the final mirror finish achieved all the facets.
Ideal, super ideal, triple o, hearts and arrows, branded and signature cuts
As if the subject of cutting was not complicated enough, now there are an ever increasing number of competing ideas about what cutting parameters are truly the best.
The concept of an ideal cut first gained popularity in 1919 when mathematician Gabriel Tolkowsky published a study of the behavior of light in a cut diamond and came up with a formula for proportions that would result in the most beautiful round diamond.
Over the years experimentation and scientific study have revealed that there are many proportion combinations that result in superb finished diamonds. In fact, the most important study on the subject ever conducted and utilizing advanced computer modeling technologies is the ongoing study by the Gemological Institute of America.
Despite all the hype in the trade as different companies go about promoting their own versions of ideal diamonds, the position of the GIA on the subject is stated in their educational materials in this way: Unfortunately, there is no proof that any one set of proportions is truly ideal. Preliminary results of ongoing research on cut suggest that many different proportion combinations succeed equally well. For this reason, GIA does render qualitative cut grades on their reports.
To underscore how complicated the subject is, despite advanced research no definitive conclusion has been reached regarding the round brilliant cut. Fancy shapes offer a mind numbing range of different variables that may defy definitive pronouncements for generations to come!
Fancy Shapes
Diamond shapes other than round are referred to as fancy shapes. Almost any shape is possible and there are new designs coming into the market regularly as new diamond cutting technologies are developed. Determining a cut grade for fancy shapes is far more complicated than for rounds, and as a result there are no rigid standards, and therefore no “ideal” or “premium” combination of proportions. To a great extent with fancies, ‘beauty is in the eye of the beholder’.
One of the most important aspects in fancies is the overall outline of the shape. The diamond’s outline will affect the eye appeal of the stone as well as the overall design of a finished piece of jewelry. Yet this remains a relatively subjective factor.
For instance, some people might prefer a long slender marquise for a design that accentuates a long slender finger. Likewise, a pendant design might favor an elongated pear shape over one with broad shoulders.
To help you understand and visualize the outline of the stone, we have included a calculation of the length to width ratio for all our fancies on each diamond detail page. In addition, we present a representative image of a diamond with a length to width ratio similar to the diamond being viewed. By knowing the length to width ratio of the diamond in the representative image and comparing that to the ratio of the actual diamond, you are able to get a very close visualization of the outline of the actual diamond under consideration.
For example, if you are looking at a marquise shaped stone and the representative image has a ratio of 1.78, and you see in the diamond details that the actual stone has a ratio of 1.85, you know that the diamond you are considering is very slightly more elongated than the representative image. Likewise, if you are looking at an oval and the representative image is 1.45, and the actual diamond has a ratio of 1.39, you know that the stone you are considering is slightly wider than the diamond in the representative image.
We hope that you find this tool helpful in selecting the fancy shape best for your taste and best suited to the piece of jewelry that you wish to create.
Our Advice:
While a good quality round diamond with an ideal cut will certainly be very beautiful, very good and premium cuts might be just as attractive without costing a premium. While no commonly accepted ideal cut parameters exist for fancy shapes, good and very good cut grades will result in the best performance. Consider the length to width ratio of the diamond and the design of the mounting when selecting a fancy shape.
