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The 5 Cs Diamond Buying Guide: Cut, Clarity, Colour, Carat, Certification

Cut, colour, clarity, carat and certification. These are otherwise known as the 5 Cs and are used around the world to classify diamonds.


The 5 Cs have a big impact on many aspects of a diamond, including its price and value, so having some awareness of these can be handy when shopping for a diamond.



The cut of a diamond refers to its shape, style, proportions, symmetry and finish. It’s formed by the angles a skilled craftsman creates when working a rough diamond into a polished one. Arguably, the cut is one of the most important factors to consider when shopping for a diamond as the way it’s cut and polished will affect its brilliance and sparkle.

Cuts are divided into three different types: shallow cut, well cut and deep cut.

Shallow cut

When a diamond is shallow cut, the light hits the pavilion at a low angle. The light travels through the diamond and exits through the sides, instead of reflecting through the table and to your eyes.

Well cut

A well-cut diamond will reflect more light and appear larger than it actually is. It can also make the face-up colour look brighter and can mask or camouflage inclusions. It is often referred to as the ‘ideal cut’.

Deep cut

A deep cut diamond may look smaller than diamonds of the same carat weight but has more depth than a shallow or well-cut diamond.




Diamonds range in colour, from white to yellow and variations can be very subtle to the eye. Colour is graded on a scale of D to Z. Diamonds towards the D end of the scale are colourless, while Z scale diamonds are light yellow.

White diamonds remain the most popular – these are considered perfect! But colourless diamonds tend to be even more desirable and valuable, particularly because they are very rare to find.

The colour of a diamond will also impact its value. It’s often the case that diamonds become cheaper the closer they are to the Z end of the scale.




The clarity of a diamond refers to small imperfections on the surface and internally. These are known as blemishes and inclusions.

Blemishes and inclusions appear naturally, whilst the diamond is still forming, therefore almost all diamonds have inclusions. However some inclusions are so small they are unnoticeable to a naked eye, whilst others are larger and more visible. The number, location, size and type of inclusion are all considered when assessing a diamond’s clarity.

Just like colour, the clarity of a diamond is graded on a scale. An FL/IF diamond is flawless, with no visible inclusions. These tend to be the most valuable and expensive.

I3 diamonds, on the other hand, have inclusions that are visible to the naked eye and tend to be of less value.



Carat is the most popular aspect of a diamond; however, it is also the most misunderstood. Carat refers to a diamond’s measurement of weight, but it’s often confused with size. One carat is equal to 0.2 grams. So, the higher the carat number, the heavier the diamond.

Heavier diamonds also are of course more valuable, but the other 4C’s are also important factors to consider in the value of a diamond. A diamond could have a high carat, but have poor clarity and colour. Consider what is most important for you and go with the one that suits your own personal taste.



Most diamonds are usually accompanied with a diamond certificate from a well-renowned diamond lab. The certificate details the diamond’s unique characteristics, including its cut, colour, clarity, carat, as well as its value and quality. Having a certificate is proof -and peace of mind- that your diamond is what the jeweller says it is. If a jeweller is unable to provide you with a diamond certificate, perhaps not is as all as it seems.

You can view our full diamond buying guide here.


Our highly skilled team of jewellers will always be on hand to help you find the perfect diamond.

Visit our boutiques in Glasgow or Aberdeen to discover our beautiful collection of diamond jewellery, from unique diamond pendants to stunning diamond rings. You can browse a selection of our diamond jewellery online here, but these items only represent a small selection of our in store stock.