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The 4 C’s of Diamonds: Evaluating Diamond Quality


Each of the 4 C’s of diamonds (Cut, Color, Clarity, and Carat) plays a role in a diamond’s beauty. The grades a diamond carries in these four areas give a clear idea of the diamond’s quality, and by extension the right price you should be willing to pay.

What are the 4 C’s of diamonds?

A diamond’s quality is determined by the 4C’s: 

  • Cut: Quality of the angles, proportions, facets, and finishing details.
  • Color: How colorless the diamond is. 
  • Clarity: How clean the diamond is of inclusions and blemishes.
  • Carat: The weight of the diamond.

These four qualities of a diamond are the key components that impact its beauty and structure. The 4C’s interact with each other within the diamond. They dictate how the diamond appears and how high quality it is. As an example, the diamond’s ability to reflect light back to your eyes depends primarily on cut quality but also on color and clarity. 

The four-diamond characteristics are graded by professionals on a consistent scale, giving you a tool to evaluate diamonds. By reviewing the 4C’s of a particular diamond, you can better determine if the diamond is of high quality.




When evaluating the color of a gem-quality diamond, it is based on the lack of hue, similar to a drop of pure water.  The less color in a diamond will give it a higher value.

The GIA created a scale from D-Z which is most widely used in the jewelry industry. The scale begins with the letter D and is considered colorless, with increasing color presence, to the letter Z.  Many of these color distinctions are so subtle, it requires a trained eye (experienced gemologist) with a set of master stones, to determine the color.

Diamond fluorescence, in its most simple form, is the effect that ultraviolet (UV) light has on a diamond. When you stand under blue light or ultraviolet light, sometimes you can see your whites get brighter or your teeth appear to glow.  Diamonds in the D to H color range with a bluish fluorescence are often considered less desirable by the trade. Some believe that a bluish fluorescence may cause a hazy or oily appearance in these diamonds, but only if the fluorescence intensity is very strong. Not all diamonds with very strong bluish fluorescence look oily, however, and they may sell for less than diamonds that do not have blue fluorescence.  With all other items being equal, a diamond with fluorescence will typically be sold 5% to 10% lower.

The difference in value from one color to another can be huge, so it is important to know that the color grade is accurate.






Natural diamonds are created when the element carbon is exposed to tremendous heat and pressure deep in the earth. This process can result in a variety of internal characteristics called ‘inclusions’ and external characteristics called ‘blemishes.’

The GIA created a scale with 6 categories, some of which were split up to create a total of 11 individual clarity grades.

Again, you need an experienced gemologist to properly determine this grade since most people will not be able to see some of the inclusions or blemishes without magnification.  A gemologist will take into account the size of the diamond, the number, size, relief, nature, and position of these characteristics, as well as how these affect the overall appearance of the stone.  While no diamond is perfectly pure, the closer it comes, the higher its value.

There can be a substantial difference in value between a VS2 and an SI1, so you need to make sure you have the correct clarity grade.



The GIA Diamond Clarity Scale has 6 categories, some of which are divided, for a total of 11 specific grades.

  • Flawless (FL) No inclusions and no blemishes visible under 10x magnification
  • Internally Flawless (IF) No inclusions visible under 10x magnification
  • Very, Very Slightly Included (VVS1 and VVS2) Inclusions so slight they are difficult for a skilled grader to see under 10x magnification
  • Very Slightly Included (VS1 and VS2) Inclusions are observed with effort under 10x magnification but can be characterized as minor
  • Slightly Included (SI1 and SI2) Inclusions are noticeable under 10x magnification
  • Included (I1I2, and I3) Inclusions are obvious under 10x magnification which may affect transparency and brilliance




Cut , is the most important factor when buying a diamond.

The ‘Cut’ is perhaps the most important aspect of a diamond quality that impacts a diamond’s beauty. Diamond Cut specifically refers to the quality of a diamond’s angles, proportions, symmetrical facets, brilliance, fire, scintillation, and finishing details. These factors directly impact a diamond’s ability to sparkle, along with its overall aesthetic appeal.

The GIA diamond cut chart grades Diamond Cut on the scale of Ideal, Excellent, Very Good, Good, Fair, and Poor. The Ideal and Excellent grades, depending on Diamond Shape, signify proportions and angles cut for maximum brilliance and fire.


Even if two diamonds are given the same grade on the diamond cut chart, cuts vary significantly among diamonds and diamond cutters. At times, a cutter may aim for maximum Carat weight, leaving the diamond too deep or too shallow for optimal light reflection. Other times a diamond may be cut to minimize the number of inclusions, improving its Clarity, but forgoing maximum sparkle. Even an Ideal cut diamond may have a yellow tint that is too noticeable and detracts from the gem’s beauty.

More importantly, though, is ensuring Cut is a focal point of your diamond selection.  The cut is the biggest indicator of beauty and should be made a priority over the other C’s. 



Diamond Carat Weight Measures a Diamond’s Apparent Size

Diamond carat weight is the measurement of how much a diamond weighs. A metric “carat” is defined as 200 milligrams.

Each carat can be subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. A jeweler may describe the weight of a diamond below one carat by its ‘points’ alone. For instance, the jeweler may refer to a diamond that weighs 0.25 carats as a ‘twenty-five pointer.’ Diamond weights greater than one carat are expressed in carats and decimals. A 1.08 carat stone would be described as ‘one point oh eight carats.’

All else being equal, diamond price increases with diamond carat weight because larger diamonds are more rare and more desirable. But two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the diamond 4Cs: Clarity, Color, and Cut.

It’s important to remember that a diamond’s value is determined using all of the 4Cs, not just carat weight.




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