An Introduction to Diamond Grading and the 4Cs

An Introduction to Diamond Grading and the 4Cs

If you are thinking of buying a diamond ring, you will have probably come across the term the “4 Cs", and you may be wondering what they are and why they are important. If this is you - read on for an introduction to diamond grading and the 4 Cs.
In simple terms, it is a system of diamond grading, according to the four categories which we associate with overall diamond quality: carat, colour, clarity and cut. These can be identified by a laboratory, using highly sophisticated technology to analyse the diamond, which is usually unset from any jewellery, and a formal certificate will be produced. 
Otherwise, the diamond can be assessed by eye to produce an estimate, but the stone remains in the setting which may make it more difficult to view fully. Some diamonds may be sold without any certification or assessed diamond grading and there’s nothing wrong with this. Whilst having a certificate gives you, the customer, more confidence with your purchase, being too focused on a particular diamond grade may mean that you overlook other beautiful diamonds and miss out. 
Whilst we wholeheartedly recommend having an understanding of what the 4Cs are to determine what is the right diamond for you, ultimately it is the diamond's unique charm that you need to fall in love with, regardless of the diamond quality!
Let’s delve into what these four key diamond grading terms mean. It is worth noting that different organisations responsible for certifying diamonds may use a slightly different language when grading diamonds, but for the purposes of this post we will focus on GIA, as it is the most prevalent.


Carat is a measure of weight of gemstones – not only diamonds, but most other gemstones will also be presented in terms of a carat weight. There are 100 “points" in 1 carat (1.00ct), so half a carat is 50 points. It is important to note that the carat weight is not necessarily an indication of size – diamonds can be cut to different dimensions and thus a 1.00ct old cut may be a deeper, higher cut and therefore appear smaller when viewed from the top (the “table’ facet of the diamond") than a 1.00ct modern round brilliant cut.
Also, generally, nice round numbers are more sought after and command higher prices, so you may want to think about being savvy and going for a stone such as the 1.82ct diamond solitaire ring below, that looks almost exactly like a 2.00ct stone, but is a little more wallet-friendly.


There are different types of diamonds which form in nature with slightly different chemical structures. This results in there being many different colours available, such as: brown, orange, pink, red, green, blue, yellow and colourless. The vast majority of the diamonds that make their way into jewellery, however, are a type of diamond which naturally form along a spectrum of colourless to yellow.
The highest grade available when diamond grading is a D, which denotes a stone that is absolutely colourless (the reason they don’t start from A is actually really boring - another company had basically got there first and GIA needed to differentiate themselves to avoid confusion). D to F are considered “colourless”G to J “near colourless”, and K to M “faintly coloured”. Anything beyond M is going to be pretty obviously tinted yellow, but the scale goes all the way to Z.
It’s generally accepted that a slight draw of colour begins to be visible from H, however this is only really noticeable if it is directly compared to a much higher colour graded diamond and an inexperienced eye would likely not see much difference. Equally, you may hear that a diamond “faces up well”. This means that the diamond may technically have a lower colour grade, but the way that the light interacts within the stone means that it looks colourless when viewed through the table.
Furthermore, a visible colour tint doesn’t mean that the diamond quality is necessarily lower. It could be an incredibly clean, inclusion free and well cut diamond, but generally people find colourless stones more aesthetically appealing.


Clarity refers to how clear the stone is, and has a direct impact on the diamond quality. As a natural product, the vast majority of diamonds contain varying degrees of  impurities within the structural fabric of the stone which developed as the diamond was formed in the earth's crust. These are called ‘inclusions’ and can vary in:
  1. Size (some will be teeny, tiny pin points whereas others may be larger and much more noticeable)
  2. Colour (some are light and therefore less visible than darker inclusions),
  3. Form (some types of inclusion are more serious than others) location (some will be located in areas of the stone where the position of the facets render the inclusion less visible). 
The GIA system starts at ‘Flawless’ (self explanatory), and moves to ‘Internally Flawless’ (may have a slight blemish on the outside of the stone), to ‘Very Very Small inclusions’ (VVS1 and 2), then to ‘Very Small inclusions’ (VS1 and 2) and on to Small Inclusions (SI1 and SI2) and Included (I1, I2 and I3).
Within the diamond grading system, if a stone is SI2 or lower, this denotes that there are inclusions present that may be visible to the naked eye (some are obvious, but some still require real scrutiny). When you get to the lowest grades of I1-3, you should know that this is described as the beauty and/or durability of the stone being impacted. If there’s a large inclusion  (such as a crack or chip), it may mean that the structural integrity of the diamond is compromised, so the diamond quality is directly affected. Although diamonds are the hardest material on earth, they develop in a grain structure similar to wood, so a serious knock can cleave a big chunk of a diamond away, especially if it already has a weakness. Clarity contributes significantly to the beauty of the diamond - the more the inclusions, the more interference as the light tries to travel through the stone, which results in a duller stone.


In order for diamonds to have the bright, sparkling appearance that we all know and love, the light enters through the table facet, and bounces off the back of the diamond so that it is reflected out through the top of the stone and into the eye of the viewer. So, diamond grading assesses the angles and proportions of the shape and facets of the diamond as these will affect how well this return of light is achieved.
Cut also assesses the general craftsmanship of the stone such as polish, symmetry of the facet arrangements, girdle thickness and the table proportion. All of these factors, if done well, contribute to maximising the return of light in the diamond and the resulting presence of brilliance (return of bright, white light), fire (the flashes of bright colour) and scintillation (the amount of sparkle) and minimising the loss of light and resulting dark patches. Cut is graded ‘Excellent’, ‘Very Good’, ‘Good’, ‘Fair’, ‘Poor’.
You may have heard the term “Triple X” diamonds, which refers to an Excellent grade for cut, symmetry and polish - but a diamond doesn’t need an Excellent in each to receive an overall cut grade of Excellent. 
And so there you have it; an introduction to diamond grading and the 4 C’s. We hope that you now feel a little more comfortable with this knowledge as you search for the perfect diamond for you. If you have any further questions of queries, please don't hesitate to get in touch! You can email us at any time.
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