How are Diamonds graded for clarity?

There are a number of factors that decide the value of a diamond but one of the most important is a diamond’s clarity. The classic definition of clarity is a gemstones ‘relative freedom from blemishes and inclusions’. In order to have a quick reference for the clarity of any given diamond jewellers often use diamond grading codes used by the GIA or IGI.

The Gemological Institute of America (GIA) uses the following grades for diamonds of different clarity:



Internally Flawless

Two categories of Very very slightly included VVS1/VVS2

Two categories of Very slightly included VS1/VS2

Two categories of Slightly included SI1/SI2

Three categories of Included I1/I2/I3


Where a diamond sits on this grading structure is decided by the prevalence of inclusions (internal irregularities in the stone) and blemishes (surface irregularities) which have an impact on the appearance of the diamond. Grading is often based on characteristics which do not have an impact the diamonds beauty or durability and are often only apparent under a microscope.


A diamond graded as flawless will have no flaws when viewed by naked eye or under 10x magnification. Flawless natural diamonds are extremely rare and extremely expensive as a consequence!


An internally flawless diamond has no inclusions but will have some surface blemishes not visible to the naked eye but that can be seen under 10x magnification. These surface blemishes can often be removed by re-polishing the diamond but this is rarely done.


Very very slightly included diamonds generally display ‘minute’ inclusions which are usually very difficult to see at 10x magnification and are not visible to the naked eye. Most stones you will see in jewellery stores are in the VVS1/VVS2 to VS1/VS2 range.


Very slightly included diamonds can have inclusions that are difficult (VS1) to somewhat easy (VS2) to see at 10x magnification. Any blemishes or inclusions on stones in this category are minor in nature.


Slightly included diamonds contain inclusions that are easy or very easy to see under 10x magnification although to the naked eye these stones will still look very attractive.


Included diamonds contain inclusions that are obvious under 10x magnification and these inclusions will frequently affect transparency and brilliance of the diamond in question. If the diamond falls into the lowest included category (I3) then it will often be deficient in clarity and durability with obvious blemishes as you look down through the table (large central facet at the top of a diamond) of the diamond.


Remember that there is a trade off in terms of the number of blemishes and inclusions that is acceptable in a stone. A lot of these characteristics add something unique to a stone like a human fingerprint is unique to each person and buying a lower grade stone means the stone you buy at any set price point can be larger. If the diamond still reflects light well and looks good under the naked eye buying a larger lower graded stone can be a very good option for many consumers.

The 4 C’s of buying diamonds

When you decide to buy a diamond engagement ring you ll often hear about the 4 C’s of diamonds but what are these 4 C’s?
The 4 C’s are carat weight, cut, clarity and colour and together they provide a great way to evaluate the quality and worth of any diamond you decide to view.

Carat Weight
The weight of a diamond is referred to as it’s carat weight. Carat weight is always measured in metric carats and one carat equals 0.200g or one-fifth of a gram.

The ‘cut’ of a diamond refers to its cutting style/facet pattern and the basic shape of the stone. The round brilliant cut style is by far the most common and describes a diamond where the stone is cut into a round shape with kite shaped facets that radiate out from the centre of the diamond. Diamonds which are not cut into round brilliant are referred to as ‘fancy cuts’.
When grading a diamond cut refers to the quality of the cut itself looking at the diamonds proportions, outline symmetry, facet placement and surface polishing. For diamonds falling in the normal colour range cut is grading on a sliding scale from excellent to poor.
Well cut diamonds reflect the light up through the centre of your stone which will give it a beautiful sparkle.

Clarity in a diamond is the absence of inclusions and blemishes which are referred to as clarity characteristics.
Blemishes refer to any surface flaws on the stone while inclusions are internal imperfections in the stone.
Clarity is graded on a scale from flawless to included. For a stone to qualify for a flawless grade it needs to have no inclusions or blemishes not just under an eye examination but also under 10x magnification exam. Very very few natural stones can achieve a flawless grade as natural processes of geological formation normally leave small blemishes on natural diamonds which are completely unique to that stone like a ‘fingerprint’ identifying a person.

This refers to the body colour or basic colour in a diamond. Body colour varies in hue, tone and also saturation.
Most engagement ring diamonds range in colour from colourless to light yellow and brown.
Colours are graded on a scale from ‘d’ which is colourless to ‘z’ which is light yellow brown or gray. This d to z range is also referred to as the normal colour range.
When a diamond falls outside the normal colour range it is referred to as a coloured diamond. These coloured diamonds come in colours such as pink, green and blue as well as deeper shades of yellow, brown and gray.



Fancy Cut Diamonds

Most diamonds are cut in the standard round brilliant style but there are a number of other popular cut styles which customers sometimes request.

fancy cut diamonds shapes

In the image above you can see the typical round brilliant shape diamond followed by ‘fancy cut’ diamond shapes. Some stones are also cut into ‘novelty’ shapes such as an animal or star for example but in the main, fancy cuts refers to the shapes above apart from the standard round brilliant.


As diamond cutting technologies have evolved this has allowed diamond cutters to develop their own unique cuts which can then be branded. Many branded cuts become more widely used after their initial patents expired.


Some of these cuts are detailed below:


Radiant Cut: this is a cut cornered square or rectangular modified brilliant diamond


Asscher Cut: dating back to the early 1900’s this is the predecessor of the emerald cut. This is a cut cornered square or rectangular step cut with wide corners that are almost octagonal in shape


Princess Cut: This is a square or rectangular modified brilliant ocasionally with corners that have bezel or french tips and a variable number of facets


Quadrillion Cut: dating back to 1979 this is a square modified brilliant style. It preceded the princess cut style but is often today referred to as the princess cut. However quadrillion cuts have a narrower range of proportions than true princess cut stones.


Trillion and Trilliant cuts: Nowadays these cuts refer to variations of triangular brilliants but originally these were trademarked names for triangular and modified triangular brilliant cut stones

Trapeze Cuts: A diamond cut into a trapezoid shape with various cutting styles is referred to as a trapeze cut stone.