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What Are the 5 Cs of Diamonds and Why Are They Important?

You might have heard people refer to the ‘5 Cs of diamonds’, but what are they actually talking about? In this blog, I walk you through each of the five things to look for when you are looking to buy a diamond.

What are the 5 Cs of diamonds?

As an introduction, the following are five things you should look for when trying to understand the value of a diamond: 

  • Cut
  • Colour
  • Clarity
  • Carat
  • Certification

I will explore each of these in more detail below and explain why it is important in determining the value of a diamond.

Related article: A Guide to Buying an Engagement Ring


Diamonds must be cut to size from the rough and this can result in a whole variety of different shapes of diamond. It is a refined art and it is easy to make mistakes when it comes to cutting so this process requires careful and dedicated work.

Diamond cutting is important because this is what reveals a diamond’s shine and sparkle. When cut in a certain way, a diamond will be mesmerizingly bright due to the way it reflects light, making it a truly beautiful stone. If a diamond is cut poorly, however, it won’t be as brilliant.

The most popular diamond cut is ‘Round Brilliant’ as it is thought to maximise the brilliance of the diamond in a round format (as the name suggests). Other popular cuts include the Princess Cut, which can be in a square or rectangular shape and reflects colour in the four corners, the Cushion Cut, which is a cross between the Round Brilliant and Princess in a softer square or rectangular shape, and the Marquise Cut, which is a unique eye shape with pointed ends.


Diamonds occur naturally in a variety of colours. Whiter diamonds are generally considered more attractive, so these tend to be graded as superior on the colour scale. However, I think those diamonds with a warm yellow tone are beautiful too!

According to the colour scale, diamonds can be graded between D and Z for their colour. A D Diamond is what is called a “colourless” diamond, and the further you move down the scale, the yellower the diamond is.

Diamonds also naturally occur in a variety of colours outside of this yellow-focused scale, including pink, green and blue - these are very rare, beautiful and valuable stones.


Next in the 5 Cs is clarity. When you have a diamond, it will naturally have some minuscule marks or ‘flaws’ which have occurred in its formation. A diamond with high clarity has very few of these marks and is considered to be rarer, more beautiful and more valuable. As with colour, a diamond can be graded on a scale when it comes to its clarity characteristics.

The scale used to assess the clarity of a diamond runs from FL (Flawless) and IF (Internally Flawless) to SI1 and SI2 (Slightly Included) and I1, I2, and I3 (Included). FL refers to a diamond which has no inclusions and no blemishes visible under 10x magnification, while I refers to inclusions that are obvious under 10x magnification and may affect transparency and brilliance.


The one thing you’re guaranteed to hear about when it comes to a diamond is ‘carat’. The carat number refers to the weight and overall size of a particular stone. Weight is important here, as well as size, because a good weight doesn’t necessarily mean a big stone - it depends on the proportions of the stone.

Furthermore, as you can tell from this list, a higher carat number does not necessarily make a more valuable diamond, as you also need to account for cut, clarity and colour, but it does have an impact on the overall value.


The final thing to consider, and the final member of the 5 Cs for diamonds, is certification. This is a sure-fire way to ensure the value and validity of a diamond, as an independent laboratory will have tested the diamond and given it a grading - its credentials of sorts. Some of the popular diamond certification agencies include the Gemological Institute of America (GIA), the British Gemmological Institute (BGI) and the International Gemological Institute (IGI).

Aside from these 5 Cs, which are of course very important in the decision-making process, there is something else that is extremely valuable when you are choosing a diamond - your instinct. You need to make sure that you feel a special connection with the diamond you choose. I feel this is most important as one can really get overwhelmed with trying to get the “best value” when taking into consideration all the factors that affect the price of a stone

Another factor, of course, is that you may have a diamond in your family that you want to set into a ring or another piece of jewellery. This is something we can do for you at Milina London with our bespoke service.

I hope you have enjoyed reading this blog on the 5 Cs of diamonds. If you have any questions at all, please get in touch.