The 4Cs

Diamonds are graded by four criteria which measure a diamond’s carat weight, color, clarity, and cut. While these are great indicators for a diamond’s quality, it is important to keep in mind that there is much more to each diamond than just the 4Cs.


Most people believe that “carat” refers to the size of a given diamond. In reality, it is a measure of weight. A diamond grading report will specify a diamond’s weight in “carats”. One carat is 0.2 grams, or 200 milligrams. Historically, the term comes from the use of carob seeds in Egypt, which weighed about that amount. The carat became a standard unit of weight in the early 20th century. In certificates, a diamond’s weight is always rounded to the nearest hundredth of a carat (0.01 carats).

diamond weight carat

Diamonds are also sometimes weighed in “points” instead of carats. A point is 0.01 carats, so a half-carat diamond would be 50 points. Not all diamonds that share the same weight will look the be the same size. This is because the cut of the diamond can affect its physical dimensions. Some diamonds may have extra weight at the pavilion (bottom part of a diamond), making the diameter appear smaller than that of a diamond which has less pavilion weight. Larger diamonds are much more rare than small ones, and it often takes hundreds of tons of rock and ore to find a single one-carat diamond.

However, size is not the most important factor when shopping for a diamond. There are many large diamonds on the market that are of inferior quality. The cut of the diamond, for example, is more critical to the visual brilliance and fire of a stone than its size. If the diamond size is the most important factor for you, be sure to not overlook the other three Cs (color, clarity, cut) when searching for a diamond.


There are several scales used for judging the color of a diamond, but the most common is an alphabetic scale widely used in the US. The Gemological Institute of America (GIA) grades diamond colors from D (totally colorless, sometimes called “white”) to Z (yellow). A colorless diamond is graded as D, E, or F, but the difference between each grade is small and usually only obvious to a trained expert. The difference is much more noticeable when comparing an F color diamond with a J color diamond. The most common color range for diamonds used in engagement rings is G-J (near colorless).

diamond color

An experienced gemologist grades a diamond’s color by first placing the diamond face-down on a white background. He then judges the level of color concentration by comparing it against a set of diamond masters. The gemologist then assigns a color grade represented by a letter to the stone, and this is recorded on the diamond’s certificate.

In nature, diamonds range in color from white (colorless) through slightly yellow or brownish. There are some stones that have chemical impurities that tint the diamond a different color such as blue, green or pink. These are called fancy diamonds and are rare and costly.

Diamonds with D, E or F color are considered colorless; G, H, I and J colors are near colorless; K, L, and M colors are a faint yellow; N through R have a light yellow tint; S through Z are light yellow. Once the color intensity surpasses Z, the diamond is considered “Fancy Yellow”, also known as Canary. The color of the stone can be affected by the mounting, so a slightly colored stone can appear colorless when properly mounted. A yellow gold mounting also makes very slight colors almost impossible to detect. Canary diamonds benefit from a yellow cup underneath, which raises their color intensity when set.

However, color alone does not make a diamond valuable. The other Cs (carat, clarity, cut) must also be considered. A colorless diamond with a poor cut is not as valuable as an ideal cut diamond that has some color of the same size.


Clarity judges how free the diamond is from imperfections. Clarity grades range from internally flawless (IF) to fairly included (I3). The higher the clarity grade, the higher the value of the diamond (and the more rare it is). Diamonds with no (or very few) inclusions are more highly valued than those with lower clarity, both because of their rarity and their visual appearance.

Flaws in diamonds come in many forms, some almost impossible to see and some visible to the naked eye. Typical flaws are:

• Pinpoint: A small white dot on the surface of the stone
• Carbons: A small black dot on the surface of the stone
• Feathers: Small cracks within the stone
• Clouds: Hazy areas within the diamond
• Crystal Growth: A small crystalline growth that looks like a small diamond within the bigger diamond

The clarity grades used by the Gemological Institute of America are:

IF-FL Flawless or Internally Flawless diamonds show no inclusions of any sort under 10X magnification when observed by an experienced grader. Internally Flawless diamond may have some minor blemishes.
VVS1-VVS2 Very, Very slightly included diamonds contain minute inclusions that are difficult for experienced graders to see under 10X magnification.
VS1-VS2 Very slightly included diamonds contain minute inclusions such as small crystals, clouds or feathers when observed under 10X magnification.
SI2-SI2 Slightly included diamonds contain inclusions (clouds, included crystals, knots, cavities, and feathers) noticeable to an experienced grader under 10X magnification.
I1-I3 Included diamonds contain inclusions obvious both to the naked eye and under 10X magnification, and may also affect transparency and brilliance.

diamond clarity

Well-cut diamonds that have many facets (such as round brilliant) make it difficult to see inclusions with the naked eye or magnification. Therefore, the best value in these cuts is often SI1 or VS2. Step-cut diamonds (such as Asschers and Emeralds) are more transparent and show inclusions easier, so a VS2 diamond or higher is recommended.

To most people, clarity is the least important of the four Cs. This is because the difference in some grades is very difficult to see except under magnification, and the difference between an SI1 and a VVS2 diamond may not be noticed except by a professional gemologist. This allows the purchaser to choose a reasonable clarity diamond and invest more in the color or carat weight of the diamond. Clarity differences have a significant effect on the value of a diamond. The cost of an IF diamond is much higher than a VS1 clarity, even though the average consumer cannot see the difference.


Cut is often thought to be the most important of the four Cs, because a good cut reflects light, giving the diamond its fire and sparkle. The cut is not the shape of the diamond, but refers to the cutting of the diamond into facets and the way in which it reflects light internally. The shape of the diamond, such as round, emerald, or pear, refers to the overall appearance of the diamond. The cut is the primary factor in the brilliance or fire of a diamond, where light seems to come from the very heart of the diamond itself.

A well-cut diamond has light entering through the table and traveling to the pavilion where it reflects from one side to the other before reflecting back out of the diamond, through the table, to the observer’s eye. This is the brilliance or “fire” of a diamond you can see easily, making the diamond appear flashier and more mesmerizing.

diamond cut grade

In the above diagram you can see that a deep-cut diamond may appear to have a higher carat weight than an ideal cut (it weighs more) but it will not have the same brilliance and fire and is a less desirable diamond. Poorly cut diamonds do not reflect the light back to the viewer properly, leaking light from the edges and bottom of the diamond.

The brilliant round diamond is cut with 58 facets, 33 on the crown and 25 on the pavilion. These facets should be uniform and symmetrical or the diamond’s ability to reflect light is affected. When buying a diamond, ask about the cut. Many jewelers will not discuss cut unless asked; a poorly cut diamond costs a lot less than a well-cut diamond, often making it look like a great bargain. However, the diamond is inferior and does not possess the sparkle we expect from a diamond.

It is often difficult for the average person to tell the difference between an ideal cut and a poor cut with a quick examination. To help grade diamonds according to cut, gemologists use a set of formulas that dictate the angles and facet sizes in an ideal diamond. The amount by which the diamond’s cut deviates from this ideal provides the lower grades. Cut may be one of the most important factors in a diamond’s appeal, so gemologists have defined several grading scales.

The most widely used grades are:


Ideal Offers the maximize brilliance possible. The smaller table sizes of ideal cut diamonds create a great deal of dispersion (“fire”) within the stone. Ideal cut diamonds are for the discerning purchaser who knows that they have one of the finest diamonds money can buy. The Ideal cut category applies only to round diamonds.
Premium In round diamonds many Premium cuts are the equal of any Ideal cut, though they can be purchased at slightly lower prices. Premium cut diamonds provide maximum brilliance and fire. Like the Ideal cut, these diamonds are also for the person who enjoys the finest diamonds money can buy.
Very Good These diamonds reflect most of the light that enters them, offering a great deal of brilliance. Often with Very Good cuts, the diamond cutters chose to stray slightly from the preferred diamond proportions in order to create a larger stone. These diamonds fall outside of the perfect table size or girdle width, although in many cases the cut range overlaps with the parameters of diamonds in the better ranges. The price of these diamonds is slightly below those of Premium cuts.
Good These diamonds reflect much of the light that enters them but their proportions fall outside the preferred range so the cutter can create the largest possible stone from the original crystal. Diamonds in this range provide the buyer with excellent cost-savings without sacrificing quality or beauty.
Fair-Poor These diamonds reflect only a small part of the light that enters them. They are usually cut to maximize carat weight over other considerations, and are often found in retail mall jewelry stores.


Brilliant or Round Diamonds

As mentioned above, a brilliant round diamond is ideally cut with 58 facets. These facets will be uniform and symmetrical on a well-proportioned stone or the diamond’s ability to reflect light will be compromised. When trying to choose a cut for a diamond, you need to look at the depth and table percentages (see diagram below). The depth percentage equals the depth of a diamond (table to culet) divided by its width. The higher the depth percentage, the deeper the stone appears. For an ideal cut round diamond, the best depth percentage is 58%-62.9%.
The table percentage is the length of the table divided by the width of the diamond. The higher this number, the bigger the table looks. For an ideal cut round diamond, the best table percentage is 53%-57%.

It is important not to confuse a small table size with a small diameter. In general, you should look for a bigger diameter and a smaller table percentage, for the most beautiful round diamonds.

The 5th C – Certification

There are several institutes around the world that grade loose diamonds and gemstones. Below are a few of the most popular ones.


GIA is an initialism for the Gemological Institute of America, which is one of the most famous diamond and gemstone testing and grading laboratories in the world. The GIA was established in 1931 and has close to 1000 employees working for it currently. The staff comprises of diamond graders, scientists, and educators about precious stones and diamonds.

The GIA defined the standards of grading diamonds by creating the 4Cs. Practically, every jeweler and diamond buyer in the world recognizes GIA certified diamonds for their grading accuracy. When buying a GIA certified diamond, an individual can rest assured that the diamond in question is graded with great attention to detail.


Forevermark is a diamond brand from The De Beers Group of Companies, which has a history of diamond expertise spanning more than 125 years. Forevermark diamonds benefit from a very rigorous grading process that goes beyond the technical qualities of the 4Cs to hand-pick only diamonds that are truly beautiful. A Forevermark diamond is also guaranteed to be brand-new, having no previous owners, responsibly mined at the source, in one of the mines owned by De Beers.

Other Certificates

There are other grading laboratories with varying reputations. For example, American Gem Society (AGS) is known to focus more on the cut of a diamond, and their grading process is considered very accurate in that criteria. Tiffany & Co. has its own grading process and a diamond certificate that comes with every diamond you buy through their retail stores.