Diamond 4Cs: Which C is the Most Important

Sharif Khan
Sharif Khan
Last Updated    EST 
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Diamonds are among the world's most valuable and highly desired gemstones, naturally formed and 100% pure carbon. Because diamonds vary immensely in quality and price, buyers must be familiar with the 4Cs. This grading system has transformed the diamond trade and is currently used by nearly every professional in the industry.

The 4Cs—carat weight, color, clarity, and cut—are critical in determining a diamond's quality and price. While the first three Cs are natural elements, the fourth one depends on craftsmanship quality since it is a human factor. We also consider the diamond shapediamond fluorescencediamond certification, and physical appearance as critical factors in determining the quality and price of a diamond.

4Cs Overview

Essential elements to consider while reviewing each C.

Diamond Carat Weight: This is simple to understand; the bigger the stone, the higher the price. However, there is a catch. The price of a 2 carat diamond, all other factors being equal, is not twice as much as a 1-carat diamond's price. It would be most likely three to four times the price of a 1 carat because scarcity plays a considerable role in determining diamond prices. Because a  2 carat diamond is scarcer than a 1 carat diamond, its price would be significantly higher.

Hint: Look for stones that are not a full carat, e.g., .95ct or 1.95ct, because diamonds' prices tend to jump once they hit a full carat.

Diamond Cut: The diamond cut is probably one of the most critical factors in how the diamond is priced, affecting its overall brilliance and fire. It is a human element often manipulated to save as much of the rough diamond's weight as possible. A diamond cut ranges between excellent, very good, good, fair, and poor. The GIA assigns a cut grade for round brilliant cut diamonds and fancy-shaped ones, such as oval-cut or princess-cut, but it has yet to finalize a grading system. However, we have developed important insights for each stone shape, and we recommend that you read them before buying a diamond.

Hint: The most crucial factors in the cut of a diamond are depth, table, girdle size, crown angle, pavilion angle, and culet. Before buying a diamond, ensure you know enough about these factors, especially table and depth. It is okay to slightly compromise on the cut of a diamond if the stone's brilliance or fire is not compromised, though you must not compromise more than 3-5% as it is a crucial factor.

Diamond Clarity: Clarity is one of those factors that you can play with, depending on your budget. Diamonds are formed over millions of years under intense heat and pressure and, as a result, often have impurities and inclusions. These inclusions are the stone's natural birthmarks and are often evaluated to determine each diamond's level of clarity. Clarity ranges between Flawless (Fl), Internally Flawless (IF), Very Very Slightly Included 1 & 2 ( VVS1/VVS2), Very Slightly Included 1 & 2 (VS1/VS2), Slightly Included 1 & 2 (SI1/SI2), and Included 1, 2 & 3 (I1, I2, I3). Stones above VS2 graded by the GIA are often considered eye-clean, implying that you may not see any inclusions in the diamond without the aid of a jeweler's loupe. In under 1-carat stones, SI1 and SI2 would be considered eye-clean. I-I3 are almost always not eye-clean unless the diamond has large black crystals.

Hint: Because SI1 diamonds are eye-clean at times, it gives you plenty of space to compromise if you are on a budget to get a lower clarity grade diamond.

Diamond Color: In white diamonds, color is probably the second most important factor after the cut of a diamond. The absence of color makes the diamond more desirable; therefore, the lower the yellow tint, the better the diamond. Color grade ranges from D to Z, where a completely colorless diamond would obtain the higher color grade of D. The Colorless range is D-F, the Near Colorless range is G-J, the Faint range is K-M, the Very Light Yellow Range is N-R, and Light Yellow is S-Z.

Hint: G is an excellent color even for an investment-grade diamond, but going as low as I/J is not a bad choice if you are on a budget. Also, in lower color grade diamonds, e.g., H, I, and J, buy diamonds with blue fluorescence as they can make them look whiter because they are complementary to yellow.

Diamond Cut

Diamond cut is one of the "four Cs" used to determine the overall quality and, therefore, a diamond's price. Most diamond certificates will include a rating of the diamond's cut, and, all other things being equal, a diamond with a better cut grade will command a higher price.

diamond cut

The methods for determining a diamond's cut rating can vary depending on who makes the assessment. To further complicate the matter from the buyer's perspective, some certificates do not detail what criteria they used to grade a diamond's cut.

If you are considering buying a diamond, it would be well worth the time it takes to understand what different cut grades mean, how they are determined, and their influence on a diamond's price. This knowledge makes you better determine a diamond's price, distinguish a good deal from a bad one, and make the best possible investment when buying diamonds.

In simple terms, the cut grade of a diamond refers to a diamond's "light performance," meaning the degree to which the diamond retains and reflects the light that enters it. A diamond with a good cut will be highly reflective and exhibit the best sparkle possible. Conversely, diamonds that "leak" light through the bottom or side are usually cut too shallow or deep, respectively, and they will thus have a less favorable cut grade.

Since it is widely acknowledged that the sparkle, also called brilliance, mentioned above gives diamonds their unique beauty, it follows that cut is what separates the most stunning diamonds from ordinary ones.

Please note that "cut" in this sense does not refer to the intended shape of the diamond. If you have ever browsed for diamonds, you have probably come across terms like "Princess cut," "Asscher cut," "Emerald cut," and so on. These refer only to stylized diamond shapes and do not indicate a cut rating.

The diamond's cut is why it shines brightly and looks beautiful. An ideally cut diamond reflects the light toward the viewer's eyes, causing the diamond to look bright and shiny. Conversely, if a diamond is cut "shallow," or if the distance from the table to the cutlet is shorter than it should be, the light will be reflected away, and the diamond will be less brilliant. Similarly, if the diamond is cut too deep, the light will shine out of the pavilion, not making the top (table and crown) appear bright and lovely.

The cut can enhance that diamond's overall quality, value, and beauty. Various cuts remarkably affect the following three qualities:

  • Brightness: The amount of light the diamond reflects.
  • Fire: The several range of colors that a diamond gives off.
  • Scintillation: The sparkle and brilliance produced when a diamond is moved.

In a well-cut diamond, the light that enters the table (the top flat facet) and travels through the pavilion is reflected and dispersed through the crown, creating a desirable effect. Unfortunately, some light leaks in a poorly cut diamond from the girdle, dramatically reducing the sparkle.

A diamond cut's quality is based primarily on symmetry, polish, and the proportions of the table size, crown angle, and pavilion depth. In most cases, the more facets a diamond has, the more brilliance and sparkle it carries. However, the depth of the pavilion also has a massive impact on this. When the pavilion's depth is too much or insufficient, the light can be lost through the sides of the stone instead of being directed through the crown.

The brilliant round-cut diamond is the most common, although many others are gaining popularity. The brilliant round cut was explicitly designed for use on the diamond, and its 57-58 well-proportioned facets make its brilliance and sparkle more noticeable than on most cuts. Yet, there are many variations of diamond cuts and combinations of proportions, directly affecting the beauty of a diamond and its value.


At this point, there is no standardized system for diamond-cut grades. Instead, each certifying authority uses its own approach to rate the cut of a diamond, making things slightly more confusing. Fortunately, the grades are usually pretty straightforward, even if the methods used to figure them out are not (more on this in a second).

Most certifiers use a five or six-point cut grading system. The typical system goes as follows, from best to worst:

Ideal: A diamond with maximum brilliance.

Premium: Nearly equal to Ideal.

Very Good: A diamond with slight light leakage.

Good: A diamond with decent reflectiveness, usually one that has been cut for size rather than brilliance.

Fair or Poor: Diamonds that reflect relatively little light.

Again, though the terminology used can differ in some cases, the Gemological Institute of America, one of the significant diamond rating authorities, grades diamond cuts as Excellent, Very Good, Good, Fair, and Poor. Hence, diamond cuts rated "Excellent" by the GIA will be roughly equivalent to those rated "Ideal" by other bodies. Additionally, some diamond vendors have a special designation for their best cuts. For example, the online diamond retailer Blue Nile has a "Blue Nile Signature Ideal" cut, referring to cuts within the top 1%.

Diamond Color

Like the cut of a diamond, the color will either increase or decrease its sparkle and fire. A diamond with less color will reflect more light than a light yellow or brown hue. This, coupled with nature providing us with few colorless diamonds, makes them more valuable and sought after.

The most common color grades are G through I since they are more abundant and affordable. Although diamonds of these grades do have a hint of color, they generally are not visible to the naked or untrained eye.

diamond color chart

Diamonds are graded according to the GIA (Gemological Institute of America) color chart:

D, E, F: Colorless. The stones in this category look completely clear and are the highest-priced. A one-carat round diamond with VS1 clarity is approximately $15,000 in price.

G, H, I, J: Near Colorless. Some yellow or brown color is visible when the stone is not mounted; when it is mounted, it appears colorless. This range is considered excellent value for the money. A one-carat round diamond with VS1 clarity costs around $10,000.

K, L, M: Light Yellow. Yellow tint shows. When mounted, it still appears tinted. A one-carat round diamond with VS1 clarity costs around $5,000.

N-Y: Yellow. Strong yellow color. These stones are not used in fine jewelry. The approximate price for a VS1 clarity, one carat round diamond is less than $3,500.

Z+: Fancy. Bright, remarkable color. Usually blue, pink, or yellow. An approximate price for a VS1 clarity, one carat round diamond is more than $10,000.

Diamond Clarity

According to the GIA, "diamond clarity refers to the absence of internal inclusions or external blemishes." Of all the diamond characteristics, clarity may significantly impact a diamond's value since a flawless piece is rare. Natural diamonds are created deep within the earth under extreme pressure, so it is not surprising that nearly all diamonds have minor flaws. There are two types of defects: blemishes and inclusions. Blemishes are external flaws found on the surface of a diamond and include chips, nicks, and scratches, most of which occur during the cutting process. Inclusions are flaws inside the diamond, like bubbles, cracks, or minerals in the center.

The GIA has developed a universal diamond clarity grading scale of 11 grades. A diamond is graded under 10x magnification, so most flaws that affect the clarity grade are barely visible to the naked eye. In addition to the inclusions' number, size, and severity, the latter's position and colors are also considered when grading the clarity of a diamond. Since no two diamonds are alike, a diamond's characteristics and inclusions make it unique and are sometimes used, like fingerprints, to identify the diamond.

The clarity grades are flawless and internally flawless; diamonds of these grades are valuable because they are rare. The next best clarity grades are VVS (very, very slightly included) and VS (very slightly included). These diamonds are more common and sought after because they are more affordable than flawless ones, though they have minor inclusions, most of which can only be seen under magnification by a skilled grader. The most common clarity grade is likely SI (slightly included). A diamond of this clarity is still considered "eye-clean" and provides an inexpensive alternative. I (imperfect), the lowest clarity grade, have more noticeable inclusions, affecting a diamond's brilliance.

diamond clarity scale

The GIA defines its clarity grading scale as follows:

Flawless (FL)

No inclusions or blemishes are visible to a skilled grader using 10x magnification.

Internally Flawless (IF)

Using 10x magnification, a skilled grader can see no inclusions and only a few small blemishes.

VVS1 and VVS2

Very Slightly Included (VS1 and VS2)

Slightly Included (SI1 and SI2)

Imperfect (I1, I2, and I3)

Diamond Carat Weight

A diamond's weight is measured in carats, with one carat equaling 200 milligrams or one-fifth gram. You may also hear the term "points" when discussing diamond weight. For example, if one carat is divided into 100 points, a one-fourth carat diamond would be called a '25 point diamond.'

Although carat weight is also used to measure gemstones, it is slightly more complicated since gemstone types may have different densities.

When written, "carat" is usually abbreviated as "ct." The abbreviation used in a jewelry piece with several diamonds is "ct TW," meaning carat total weight (the sum of each diamond's carat weight). However, it is usually shortened to "ctw." The value of such a jewelry piece may be less than that of a similar item of the same carat weight with only one diamond. Diamond solitaires are rare; therefore, a 1ct Diamond Solitaire ring will be worth much more than a similar one ctw ring with a smaller diamond.

Likewise, diamonds of the same carat weight and size might have different values because one may have better color or clarity. The cut of a diamond significantly affects the diamond value and carat weight. Hence, some diamond cuts hold more volume than others.

The Four Cs, as outlined above, are the main characteristics that affect the value of a diamond. However, the fact that they classify the diamond's unique beauty and standardize the grading system to ascertain its quality carries equal significance. Therefore, we recommend that consumers read about diamond grading and other related jewelry information.