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What are the 4 C's, and what makes them important when buying diamonds?

The quality of diamonds is translated into the 4 C's:

  • Carat – the weight of the diamond.
  • Colour – a clearer diamond colour means higher quality.
  • Clarity – fewer imperfections means the diamond reflects more light and sparkles more.
  • Cut – refers to the proportions of the stone, the symmetry and the diamond brilliance.

The 4 C's not only provide verifiable information about the quality of your stone, they also make it possible to make your diamond traceable. When you are going to buy diamonds, you will always get a certificate that proves the value of your diamond.


Carats in diamonds mean the weight or the size of the stone. 1 carat equals 0.2 grams and is expressed on a scale of 100 points or 200 milligrams. The scale gives a very precise diamond weight and is rounded off to two decimal places.

The carat weight can sometimes seem to differ due to different cutting methods, but will always express the same weight. Some diamond cuts look optically larger than others because of the proportions of the diamond.

For diamond jewelry, carat refers to the total of all the included diamonds. A diamond necklace with 10 stones of 0.30 ct. will therefore be a necklace of 3.00 ct.


Most diamonds suitable for jewelery have a colour ranging from white to yellow. The correct colour of a diamond is determined based on an internationally accepted colour set, the master set, developed by the GIA. The colour ranges from D, colourless and most coveted, to Z, the most yellow.

If you are interested in buying diamonds for a pure investment, you should look for a higher colourlessness than if you want to buy diamonds in jewellery.

The names of colours have changed over time, so you might encounter terms in the diamond world that you have not heard before when you are ready to buy diamonds. However, the quality requirements concerning colour have not changed.

A diamond can also have other colours such as brown, orange, pink, blue and more. The most intense of these colours are named 'Fancy Coloured' and belong to a separate category. The 'Fancy' name is also mentioned on the certificate for your diamond. Coloured diamonds are extremely rare and therefore very expensive.

The grades of coloured diamonds are categorized into 9 subdivisions that all have a different nuance based on colour, colour saturation and depending on the individual stone. In order of least colour to most colour, they get one of the following names:

  • Faint
  • Very Light
  • Light
  • Fancy Light
  • Fancy
  • Fancy Intense
  • Fancy Vivid
  • Fancy Dark
  • Fancy Deep


'Faint' shows the lightest colour that a diamond graded as 'Fancy Coloured' can have. 'Fancy Deep' is the deepest and most expensive colour saturation. Buying coloured diamonds is often very lucrative but requires a higher investment than buying colourless diamonds.


To determine the clarity or brightness of a stone, an expert must be consulted. He examines the stone under a magnifying glass that magnifies the inside of the diamond 10 times. If no impurities, also known as blemishes, are observed under these conditions, the stone is classified as pure.

Most diamonds are created with birthmarks known as inclusions or imperfections. The fewer there are the more light the diamond reflects and the more beautifully it shines. This, however, does not mean that a diamond with inclusions cannot be eye-clean.

Buying diamonds in jewellery can often be more economical, since you can easily choose eye-clean diamonds. For investment diamonds, however, a lower brightness is less suitable.

The clarity of the diamond can be influenced by two kinds of impurities or flaws. External impurities are found on the surface due to wear or damage during cutting. By contrast, internal impurities are located inside the stone and form during the creation process. There are 3 types of inclusions:

  • Black or dark spots (spots) - dark spots that occur in the carbon phase
  • Veils (clouds) - microscopic veil-like inclusions that weaken the brightness
  • Cracks (plumes or feathers) - molecular cracks in the composition of the carbon structure of the diamond. This is the most common type of inclusion.

Cut quality

The cut shape is the most important feature of a cut diamond. This is the only value-determining factor that is influenced by man, but it does influence the diamond’s brilliance the most. What is a diamond brilliance? The brilliance of a diamond refers to the amount of light reflected by a diamond. The amount of brilliance depends on the cut of the diamond. The cutting process is therefore the most important factor to determine the value when you want to buy diamonds.

The cut shape refers to the proportions of the parts of the cut diamond, the symmetry and the brilliance. When the pavilion of the diamond is too deep or too shallow, light will escape through the sides and the bottom of the gemstone.

In a well-cut diamond, almost all the light will pass through the crown. The size of the table varies depending on the cut shape and affects, among other things, the optical size of the diamond. The girdle is mainly responsible for strength and is described instead of graded like the rest of the cut. The bottom of the diamond, often a slightly honed point, is called the culet. This miniscule facet is often not visible to the naked eye and contributes to the brilliance.

Specs of a diamond - BAUNAT

The cut quality is determined depending on the cut shape. Other shapes than the standard round cut are called 'fancy shapes'. The best-known shapes are marquise, pear shape, oval shape, heart shape and emerald. The brilliant is the name for the round cut with 57 facets, the cut shape that sparkles most of all possible types.

Different diamond shapes - BAUNAT

Would you like to know more about how diamonds get their value? Are you interested in buying diamonds in any form? Watch this video from the HRD with more information about diamonds and certificates, or ask the diamond experts at BAUNAT for advice on your investment.


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