Quality criteria for diamonds: What do the 4 C’s mean?

Diamond quality the 4 C's: Carat, Clarity, Colour, Cut
Diamond quality the 4 C's: Carat, Clarity, Colour, Cut

The quality of a cut (faceted) diamond is determined on the basis of 4 strict criteria which are internationally valid and recognised.

Click on one of the 4 C’s to find out more:

  1. Carat - the weight of a diamond
  2. Clarity - the clarity of the diamond
  3. Colour - the colour: from perfect white to yellow
  4. Cut - the cut of the diamond

Diamond Certificates: The Fifth C

You often hear of a fifth C, when referring to diamond certificates. Regardless of the diamond institutes like Gemological Institute of America (GIA), Hoge Raad voor Diamant (HRD) or International Gemmological Institute (IGI) all institutes determine the quality of a diamond on basis of the above mentioned 4 criteria.

The diamond gets an individual certificate in which an evaluation of its quality that's recorded according to the four criteria. The institutes do not estimate the actual value of the diamond. The certificate serves as a basis for pricing between buyer and seller. It contains information about the properties of the certified diamond. The internationally valid quality criteria provide security for both sides.

Origin of the name diamond

The word diamond is derived from the Latin word "diamantem", a variant of the Greek word "adámas".

1. Carat - the weight of a diamond

The weight of diamonds is expressed in carats, with 1 carat (abbreviation: ct) weighing 0.2 grams. A 1 gram diamond therefore has a weight of 5 ct. Although it is possible to get diamonds in different intermediate sizes, there are typical diamond sizes that are most popular with buyers and jewellers.

The smallest cut stones have a diamond weight of 0.01 ct. The well-known round brilliant cut is only available for stones weighing 0.05 ct. or more.

Diamond sizes

Diamonds weighing 0.25 ct. are known as quarter-carats. A popular intermediate size are stones with 0.30 ct. and the third carat with 0.33 ct. Half-caratstones with 0.50 ct. and the famous one-caratstones with 1.00 ct. are the classics. They are priced way above the smaller stones.

In order to see more diamond sizes and to get a better idea of what they look like, just check our detailed PDF-overview of the different diamond sizes.

2. Clarity - the purity of the gemstone



The fewer inclusions of foreign material are found in a diamond, the higher its purity. And the purer - i.e. free of inclusions - and clearer the diamond, the more valuable it is. The price rises exponentially with increasing purity.

"Flawless" is certainly the best-known term when it comes to the purity of diamonds. It is being referred to a "flawless diamond" if no inclusions are visible even at ten times magnification. While larger inclusions (everything from purity class PI2) can also be seen with the naked eye, smaller inclusions are only visible to the expert under a magnifying glass. For the purity of a diamond there are the following internationally valid purity classifications:

Term Meaning Explanation
if internally flawless flawless - except for possible surface traces from the processing
vvs1/vvsi very, very small inclusions Inclusions are extremely difficult to see for an experienced specialist, even at 10x magnification
vvs2 very, very small inclusions Inclusions are extremely difficult to detect even at 10x magnification
vs1/vsi very small inclusions Inclusions are very difficult to see, even at 10x magnification for an experienced specialist
vs2 very small inclusions Inclusions are difficult to detect at 10x magnification
si1 small inclusions Inclusions can be seen by a specialist at 10x magnification
si2 small inclusions Inclusions are visible at 10x magnification, but not with the naked eye
pi1 Pique I Inclusions are slightly visible to the naked eye, but do not diminish the brilliance of the diamond
pi2 Pique II Inclusions visible to the naked eye, reduced brilliance
pi3 Pique III Inclusions easily visible to the naked eye, reduces brilliance significantly

What kind of inclusions can occur?

The inclusions are basically divided into two groups, inclusions of foreign material and scratches.

Inclusions of foreign material are divided into the groups crystals, clouds and feathers. Crystals are tiny minerals that are enclosed in diamonds during their formation. Clouds are cloudy spots, that consist of an arrangement of many small crystals and can only be seen under 10x magnification. Feathers are fractures and cracks in a stone that, when relatively small, only slightly diminish the value of the diamond. However, if they are large, they can affect the diamond structure, and in the worst case, the diamond can break. Clearly pronounced feathers considerably reduce the value of the diamond. Therefore, these stones are only classified as pique diamonds (purity class pi1 to pi3).

The scratches (blemishes) are impurities or stains on the surface of a diamond. These flaws are usually not visible to the human eye. A diamond that is completely pure inside and only has one impurity on the outside can even be classified with the degrees of purity by the renowned Gemmological Institute of America (GIA).

3. The colour: from very fine white to yellow

In its purest state, a diamond is colourless. If a diamond is coloured, it is mainly due to inclusions. The colouring of a diamond is therefore often directly related to its purity. The colouring is caused by the different physical properties of the diamonds and by the colouring properties of metals embedded in the stones. These influence the physical structure and thus create colour effects. Only diamonds with brown and yellow hues get their colour from external influences. In rare cases, nature produces diamonds that are pink, red, blue, green or black.

Term GIA RAL-Category Definition
River D Very fine white + Diamonds of these colour grades appear colourless even to the expert when viewed through the colour chart.
Top Wesselton E Very fine white
F Fine white+
G Fine white
Wesselton H White
Top Crystal I White Small diamonds of these colours also appear colourless to the expert when viewed through the table. Larger stones show a slight discoloration.
Crystal J  Shlighty tinted white
K Tinted white
Top Cape M Slightly yellowish Diamonds of this  dieser Farbgrade weisen eine zunehmende, auch ohne optische Hilfsmittel erkennbare Farbe auf
Cape N Yellowish
Light Yellow bis Slighty yellow
Yellow Z Yellow


How is the colour of the diamond determined?

The Gemmological Institute of America (GIA) has developed the classification of diamonds. The first step was to define "masterstones" which stand for one colour each. The scale starts at D (transparent, highest colour) and ends with Z, whereby the stones from class M become more and more yellowish or brownish.

Also read an explicit comparison from top Wesselton and Wesselton.

Diamond colours from colourless (D) to light yellow (Z) briefly explained

D: 100 % colourless
D is the highest level and is extremely rare and very expensive.

E, F: colourless
Exceptionally transparent. With these stone qualities it is extremely difficult to detect a colour difference of 100% colourless. Diamonds that are classified as E or F are extremely rare and also very expensive.

G, H: almost colourless
These diamonds are colourless for non-experts, professionals recognize a minimal colour cast when they compare the stones to 100% colourless diamonds. These diamonds are still very rare, but offer an attractive price/performance ratio. The colours G or H are recommended for engagement rings.

I, J: almost colourless
The colouring can already be seen with the naked eye. This colour level is most frequently used in all types of jewellery and is hardly visible when framed, e.g. in a ring

K-M: yellowish
Here a clear yellow cast is already visible, even for a layman

N-Z: light yellow
Clearly visible yellow, not suitable as a gemstone.

The influence of fluorescence

Under UV light, many diamonds show the same effect as a white T-shirt in a night club, they glow. The intensity of the phenomenon known as fluorescence is classified into the categories none, faint, medium and strong. Fluorescence is considered a negative property of a diamond, because it causes the stones of the highest quality (class D-H) to appear milky or cloudy. For diamonds with a poorer colour classification (I-J), however, fluorescence can also have a positive effect: slightly yellowish stones appear whiter due to fluorescence.

4. The cut: excellence is demanded

The technical ability to perform particularly precise diamond grinding has only been available since the 20th century. The mathematician Marcel Tolkowsky wrote in his doctoral thesis about the proportions and symmetries of diamonds and developed the brilliant cut, which has at least 57 facets.

The classic diamond with a round brilliant cut

The best-known and best-selling diamonds are characterised by their classic round brilliant cut. A diamond's "fire" can only unfold perfectly with this cut.

Even someone with an untrained eye can spot the quality of the different cuts when looking into the jewellery display of any jeweller's. While some diamonds seem almost lifeless and not very shiny, others seem to sparkle.

As cutting diamonds is an extremely challenging process - due to the hardness of the material - the following applies: The cleaner and more accurate the cut, the higher the price the diamond can achieve on the market.

Other diamond shapes

Navette   Princess   Baguette   Oval   Pear
Diamant Navette   Diamant Princess   Diamant Baguette   Diamant Oval   Diamant Tropfen


What is a solitaire ring?

There are innumerable variations of the diamond ring. Does it really have to be a solitaire ring for a proposal? Surveys confirm: most women say yes. There is a reason why the diamond solitaire ring is the most popular engagement ring type in the world. So, if you want to maximise your chances of getting a "yes", choose a solitaire ring for your proposal.

Set in a prong setting, the diamond receives a unique radiance, as the light rays reach the diamond from different sides. This causes the diamond to unfold it's maximum brilliance. The round cut diamond with at least 57 facets (surfaces) is called brilliant. This special type of cut is what experts call a brilliant cut.

Among the wide range of diamond rings available, the solitaire ring always stands out. The single diamond transports the beautiful symbol of love for a unique, irreplaceable partner. The beautiful diamond is regarded worldwide as a symbol of love and eternity. A diamond solitaire ring conveys this image in a unique way.

A solitaire ring for the engagement?

There are innumerable variations of the diamond ring. Does it really have to be a solitaire ring for a proposal? Surveys confirm: most women say yes. There is a reason why the diamond solitaire ring is the most popular engagement ring type in the world. So, if you want to maximise your chances of getting a "yes", choose a solitaire ring for your proposal.

The diamond price for a round diamond in a solitaire ring does not differ from the price of differently cut diamonds. A well-cut diamond can reflect a lot of light due to the elaborate diamond cut. With a unique sparkling solitaire ring, a proposal becomes a romantic experience that will be remembered forever.

Diamond replica (zirconia)

Zirconia is a diamond imitation that is used to make jewellery. When processed well, zirconia looks very much like a real diamond at first sight. The material zirconia is produced artificially and is much cheaper than a real diamond. It is often used as a substitute for diamonds.

Zirconia - less durable, quickly cloudy

Zirconia is vastly inferior to a real diamond in its hardness and therefore breaks and becomes cloudy much faster. Zirconia is particularly suitable for fashion jewellery, which is not intended to last for a long period. Zirconia is only suitable for jewellery that will be worn only a few times.

Learn more about our shop and diamond rings

Learn more about our 5 good reasons  and discover classic solitaire engagement rings.

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