The 4Cs of diamonds


The 4Cs of diamonds

Diamonds are not only treasured for their beauty but also for their unique features, which make each stone unique. The universal standard for assessing these prized gems is known as the 4Cs: Color, Clarity, Cut, and Carat Weight. 

Established by the Gemological Institute of America (GIA), the diamond 4Cs have become the benchmark for evaluating diamonds, and are counted upon by industry professionals worldwide. Having knowledge of the 4Cs allows you to make informed decisions when it comes to selling and buying diamonds, or simply appreciating their inherent value. 

The concept originated in the 1940s. At the time, those in the diamond industry would simply differentiate between stones by using terms such as “made well” or “poorly” for the quality of a diamond. When it came to colors, terms such as “river” or “water” were used for colorless gemstones while “cape” became the popular term for diamonds deriving from the Cape of Good Hope region in South Africa.

The founder of the GIA, Robert M. Shipley, decided there had to be another way to articulate what makes diamonds valuable. For this, he devised the 4Cs: color, clarity, cut, and carat weight. This concept was straightforward yet groundbreaking and helped his students to remember the key characteristics of a faceted diamond.

What makes a diamond valuable?

Diamonds come in a variety of different shapes, sizes, and colors. In other words, each is unique, with its own particulars and internal qualities. There are certain characteristics that make some diamonds more valuable than others. This is where the diamond 4Cs are useful, as the value of a gemstone depends on its combination of classification according to diamond color, cut, clarity and carat.

What are the 4C types of diamond?

  • Carat (Weight)

The carat of a diamond relates to its weight. To give you an idea, a carat is approximately the weight of a small paper clip. This is measured with exacting precision, for example 0.2 grams (200 milligrams) is equivalent to one metric carat.


When weighing a diamond, the figure will be rounded to the nearest thousandth of a carat, followed by the nearest hundredth. Even the tiniest fraction of a carat can change the price of a diamond by thousands of pounds – however, this of course depends on the other qualities of a diamond.

Larger diamonds are harder to come across than smaller ones, which makes them more rare. As a result of this, they are typically worth more. A larger stone will be more expensive per carat than say, 4 smaller stones.

  • Clarity (Purity)

Diamonds have internal features called inclusions. These might be minerals that become trapped inside when the diamond is formed, for example. Surface irregularities called blemishes. These include scratches on the diamond surface. Together they make up clarity characteristics.  It is the absence of these that determines a diamond’s clarity.

Typically, as clarity increases (given that all of the other diamond 4cs are equal), the value of a stone increases. A diamond at the top of the GIA clarity grading scale is considered “flawless”. For this, it must have no apparent inclusions or blemishes when inspected under ten-power magnification. This type of diamond is so rare, that many experts and industry professionals go their whole careers without ever seeing one with their own eyes.


The quality of diamond we usually see on the market tend to be middle of the range when it comes to their clarity grading score. The clarity grading score comprises 11 grades: Flawless, Internally Flawless, Very (two categories), Very Slightly Included, Slightly Included (two categories), and Included (three categories). The location of the blemish or inclusion can have an impact on where it sits within these criteria. For instance, a blemish to the side will have less of an impact than one in the center of the stone.


While inclusions and blemishes can negatively impact a diamond’s value, they also help diamond valuers to identify fake diamonds and scientists to understand how a diamond has formed. They can also help to identify the difference between two diamonds that look very similar to the naked eye.

  • Color

Most diamonds have yellow or brown hues within them, which is why colorless diamonds score higher on the color grading scale. This means a colorless diamond is considered rarer than a light yellow diamond, for example. Even if 2 diamonds have the same cut, clarity, and carat, the color alone can give them wildly different value.


This difference might not be noticeable to the naked eye. This is why, to assess the quality of diamond color, the GIA will compare them to masterstones under controlled lighting. These are round brilliant diamonds of a specific color on the GIA D-Z grading scale. The D-Z grading scale starts with the letter D (which represents colorless diamonds) and increases to Z with the presence of color within a stone.

  • Cut

A diamond’s appearance is largely determined by its cut. Its dazzle will depend on the way its facets have been cut, with each angle impacting the amount of light that reaches the eye. Diamonds with many different facets that have been beautifully polished will allow the light to interact in a way that makes it appear bright and sparkling. 


With a carefully cut diamond, there are 3 optical effects at play. These are brightness (how it reflects white light), fire (flashes of color), and scintillation (aspects of light and dark). To achieve a clear and sharp appearance, there needs to be sufficient contrast between a diamond’s external and internal reflections. The arrangement, contrast, and sizing of these different reflections are called patterns. 


Along with referring to how a diamond interacts with the light, its cut is graded according to the following scale: Excellent (EX), Very Good (VG), Good (G), Fair (F), and Poor (P). Many people are familiar with popular diamond cuts such as pear, emerald, and brilliant cut. To achieve these precise levels of symmetry and proportions, takes spectacular workmanship and many years of training. 

A diamond’s depth can also impact the way it is cut. For instance, shallow-cut diamonds allow light to exit the stone from its sides, as opposed to just reflecting off the top. In contrast, the way light escapes from deep-cut diamonds means they can appear smaller than diamonds of a similar carat weight. The most favored depth of diamond is known as an ideal cut. This type of diamond is meticulously angled for optimum reflection and luminosity.

Not only does a stone’s cut play a significant role in what makes diamonds valuable, but it is also one of the most technically difficult to grade. For a typical round-cut diamond, in addition to the categories of brightness, fire, and scintillation, a grader will assess its weight ratio, symmetry, durability, and polish.

Schedule your professional diamond appraisal

In summary, the importance of the diamond 4cs cannot be underestimated. They are an integral part of diamond history, which still to this day are relied upon as the benchmark to assess the qualities of a diamond.

If you are considering selling your diamond, get in touch with our expert team of GIA-certified gemologists today to book your professional diamond appraisal. Find out your diamond’s color, cut, clarity, and cut, as well as what it might be worth in the current market.