The four Cs are: Carat, Colour, Clarity and Cut. These are the four value factors that professionals use to grade, compare and value diamonds. This grading system was developed by the GIA in the 1940s and universally used by all respected jewellers to provide objective standards in the evaluation of a diamond.

Understanding the 4Cs will help you to make the right choice.


Carat is the unit measurement of diamond weight.
One carat is 1/5 gram. Sometimes one carat is referred to as 100 points.
Diamond weights less than 1 carat are expressed as points; for example 0.50 carats diamond is referred to as a 50 pointer. Diamond weights greater than one carat are usually expressed in carats and decimals. For example a 1.45-carat diamond is expressed as “one point four five carats”.

Diamonds of the same weight can have very different values depending on the other value factors of cut, colour and clarity.

What Carat Size Should I Buy?

Buy whatever size you like, just make sure you set a budget first.


The most popular diamond is white (colourless), but diamonds also come in all other colours too such as pink, cognac, black, champagne, yellow, blue and red. These are called fancy coloured diamonds and are often valued higher than a “white” diamond. As for “white” diamonds, the colour grading scale begins with the letter D, which is colourless and the most expensive, and continues with increasing presence of colour to the letter Z. The bulk of the diamond market falls in the high end of the near colourless range.


Use this image, but take away the copyright and fancy yellow and change the fonts.

What Colour of Diamond Should I Buy?
Colour is very subjective. Many of these colour distinctions are so subtle they are indistinguishable from the next colour grade to the untrained eye. You should buy whatever colour grade you like and which falls in your budget. If you are buying a few diamonds for one jewellery piece, try and make sure they are similar if not the same colour grade as each other.


Most diamonds contain natural internal inclusions or surface blemishes. The amount, size, type and position of these flaws affect the value. The clarity of diamonds are graded as:

FL –             Flawless, extremely rare.
IF-             Internally flawless, very rare

VVS1 and VVS2 –     Very very slightly included. Inclusions are difficult for a skilled grader             to see under 10x magnification.
VS1 and VS2 –     Very slightly included. Minute inclusions slightly visible under 10x                 magnification.
SI1 and SI2 –         Slightly included. Inclusions detectable under 10x magnification.
I1, I2 and I3 -        Included. Visible to the human eye.


What Clarity Grade of a Diamond Should I Buy?

Flawless diamonds are the rarest and the most expensive. However, diamond does not have to be flawless or need to be a VVS grade to be stunning.  

The safest bet is to buy diamonds with clarity of SI2 or better.

SI1 and SI2 grades are eye-clean, which means the inclusions are not easily visible to the human eye. If the cut is excellent, these grades can be an excellent choice for both value and appearance.

Avoid I1, I2 I3 clarity grades for fine engagement rings as these grades have inclusions that would affect the brilliance and durability.


Cut directly affects a diamonds beauty, which is why most jewellers say it the most important factor. The beauty of a diamond comes from the interaction of light and it is determined by three attributes: brilliance, fire and scintillation.

Brilliance is the ability to reflect light from a diamond; fire the ability to disperse light into the colours of the spectrum; and scintillation is the flashes of light or sparkle when a diamond is moved in the light. An excellent cut diamond gives a diamond its brilliance and its fire and therefore its beauty.

Diamonds that are cut too deep or too shallow lose light that spills through the side or bottom. As a result, poorly cut diamonds are less brilliant and certainly less valuable. A diamond that is cut to good proportions reflects light internally from one facet to another and then disperses back through the top of the stone. A diamond that is well cut will display maximum brilliance and fire.

The cut scale as determined by the GIA is Excellent, Very Good, Good, Fair and Poor.

What Cut Quality of a Diamond Should I Buy?

For engagement rings, you should look for a Good, Very Good or Excellent cut diamond, which has good brilliance and sparkle. Brilliance is the first thing people notice. You can learn to judge brilliance with the naked eye by comparing with many diamonds. Once you can recognise a well cut brilliant diamond with your eyes you are well on your way of finding the perfect diamond.

Beauty Is In The Eyes of The Beholder
The 4Cs provide a way to objectively compare and evaluate diamonds, but grading alone can’t describe a diamond’s mysterious and captivating beauty – for that you will have to see the diamond yourself and trust your eyes and make the call.


Fluorescence is the visible light some diamonds emit when they are exposed to invisible ultraviolet (UV) rays. On a GIA Diamond Grading Report, fluorescence refers to the strength, or intensity, of the diamond’s reaction to the long-wave UV, which is an essential component of daylight. The light emitted lasts as long as the diamond is exposed to the ultraviolet source.

Is fluorescence common?
Yes. Of the diamonds submitted to GIA over the past decade, approximately 25%-35% exhibit some degree of fluorescence. However, only 10% of those show strengths of fluorescence that may affect appearance (ie. Strengths noted on laboratory reports as medium, strong, or very strong). In more than 95% of the diamonds that exhibit fluorescence, the colour is seen in blue. In rare instances, the reaction is yellow, white, or another colour.

What impact does fluorescence have on the appearance of a diamond?

GIA studies show that, for the overwhelming majority of diamonds, the strength of fluorescence has no widely noticeable effect on appearance. In many instances, observers prefer the appearance of diamonds that have medium to strong fluorescence. In rare cases, some diamonds with extremely strong fluorescence may appear hazy or oily; fewer than 0.2% of the fluorescent diamonds submitted to GIA exhibit this effect.

Does fluorescence compromise the structural integrity of the diamond?
No. A diamond that fluoresces has the same integrity as one with no reaction to UV. Submicriscopic substitutions and/or shifts in the diamond structure can cause fluorescence as well as prevent it. Nothing in either instance inherently weakens or is bad for the diamond.

The above notes on fluorescence are from the GIA.