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What are the 4Cs of Diamond Grading?

What are the 4Cs of Diamond Grading?

Cut, Colour, Clarity and Carat weight are what make up the 4Cs of diamond grading.

These 4Cs act as a universal language for categorising and describing diamonds to determine their quality and value. They apply to naturally mined, lab-grown and Solar Diamonds, with all four of these characteristics impacting a diamond’s appearance. 

The need for categorisation came about in the 1940s by the GIA (Gemological Institute of America) as consumer interest boomed for these precious gems. The standardisation was created to help to allow the general public and jewellers to speak the same language with regards to quality and to ensure a standardisation of pricing as well.

The 4Cs act as a consistent scale, giving gemologists a tool to accurately evaluate diamonds to determine their quality in a language that is understood by all. When working together in harmony, they come together to create something magical.

What do the 4Cs of diamond grading stand for?


The cut refers to how a diamond has been shaped and faceted, which directly impacts its sparkle, brilliance, and overall beauty. A well-cut diamond allows light to enter, reflect off its facets, and exit through the crown, creating the captivating play of light and sparkle that diamonds are known for. 

When talking about cut, we typically think of shape (such as round, oval, emerald, princess, pear and cushion) but the cut of a diamond actually refers to its facets. It’s how the light interacts with these facets that distinguishes a higher-quality of diamond. Skilled workmanship and laser cutting along with symmetry and polish, delivers the maximum return of light, completely unique to diamonds. 

The GIA have a specific scale of cut ranging from Ideal, Excellent, Very Good, Good, Fair and Poor. The Ideal and Excellent grades, depending on the diamond shape, signify proportions and angles cut for maximum brilliance and fire. However, to the untrained eye it may be very difficult to distinguish the cut grade. 

Some terms you may come across when referencing the cut of a diamond are:

Brightness: The internal and external white light that reflects from a diamond

Fire: The scattering of white light to produce a rainbow of colours

Scintillation: The amount of sparkle a diamond has, and the combination of light and dark areas caused by reflections within the stone


Interestingly, in terms of the 4Cs relating to a white diamond, colour actually refers to the lack of colour. Diamond colour is evaluated based on how colourless or how much colour is present within the stone. The GIA grades colour on a scale from D to Z to distinguish quality. D is the highest grade and represents a completely colourless diamond and Z indicates a noticeable tinge of light yellow to brown shades. Special lighting specific to diamonds helps professionals view the colour of diamonds accurately. 

While the diamond colour scale provides an example of how each grade appears, factors including cut, carat weight and shape, may impact how colour appears differently among different diamonds.

It is also worth noting that typically, the naked eye cannot tell the difference between two adjacent colour-graded diamonds, though this may be significantly reflected in the price between the two stones. It is worth checking the opinion of the gemologist in your appointment to ensure that you get the best-suited diamond for you.


A diamond's clarity refers to how ‘clean’ a diamond is. Formed from carbon through intense heat and pressure, it is natural for diamonds to include internal blemishes and inclusions, as this is part of their makeup. However, for customers, included diamonds are not as sought after due to their sometimes visible imperfections. The GIA’s clarity scale helps determine the value and quality of a diamond through its level of inclusions and blemishes. 

The term “eye-clean” is often used when discussing diamond clarity. This refers to inclusions or internal blemishes that may be visible only under magnification, and not to the unaided eye. Often, the diamond clarity grading will determine the inclusions visible in the diamond. But it can occur that two diamonds of the same clarity grade may appear slightly different as one may be eye clean and the other not, depending on where the inclusions are placed inside the stone.

The scale of clarity is categorised by:

Flawless (FL): no inclusions or 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 professional to see under 10x magnification

Very Slightly Included (VS1 and VS2):  inclusions are observed with effort under 10x magnification but are minor

Slightly Included (SI1 and SI2): inclusions are noticeable under 10x magnification

Included (I1, I2, and I3):  inclusions are obvious under 10x magnification which can affect the transparency and brilliance of the diamond

Carat Weight

The final of the 4Cs; carat weight is what most people associate with when referencing diamonds. The carat weight measures how much a diamond weighs. This is the most accurate gauge for measuring diamonds as two one-carat diamonds may differ in size depending on the shape of the diamonds and how they are cut. 

One carat is defined as 200 milligrams, with each carat divided into 100 points, allowing for precise measurements to a hundredth decimal place, so one-carat measures 0.2 grams. The term carat is derived from the carob seed, which measures the same 200 milligrams, this seed was used as it was seen as a reliably consistent weight. Using carats as a measuring tool was standardised in 1907, creating a universal system to prevent any varying carat weights.

How do the 4Cs come together? 

The way the 4Cs interact is crucial as they all work in harmony together to create a sparkling diamond. Other factors affect quality too, a diamond's symmetry, polish and girdle condition all contribute to its value and final price.  It is important to purchase this landmark jewellery piece from reputable jewellers, with a trusted gemologist team who have your best interests at heart.  

Today, the 4Cs are the universal method for grading diamonds, used anywhere in the world. The 4Cs act as an incredibly helpful tool not only for professionals, but for customers wishing to purchase a diamond too. Through cut, colour, clarity and carat weight, customers gain a knowledge and understanding of what determines the quality of a diamond, and therefore its final price. 

To learn more about diamonds and find the best one for you, get in touch and our expert team of trained gemologists will be happy to help you find your perfect diamond.