5 Essential Things You Need To Know Before Buying A Diamond

September 5, 2020

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In the Diamond industry, the Four C’s are generally accepted as the key benchmarks to measure a quality diamond. The Four C’s – Clarity, Colour, Carat and Cut – impact a diamond’s appearance and value. It is important to note that one should look at the Four C’s combined in order to get an accurate picture of how much a diamond is worth.


It takes expert craftsmanship to turn a rough diamond into stone that is ready to be fitted into a piece of jewellery. The most important (and difficult) part of this craft is achieving an excellent diamond ‘cut’. If cut well, the diamond is fashioned so that its proportions, symmetry and polish enable the diamond to sparkle at its fullest.

In order to determine how well a diamond has been cut, the GIA takes into account:

• Brightness: Internal & external white light reflected from a diamond

• Fire: The scattering of white light into all the colours of the rainbow

• Scintillation: The amount of sparkle a diamond produces

• Weight: A diamonds weight relative to its diameter

• Girdle Thickness: Affects durability

• Symmetry: In relation to its facet arrangement

• Quality: In relation to its polish on the facets

By taking into account all these factors, the GIA measures the quality of the craftsmanship that has gone into the cutting of the diamond, arriving at a scale that goes from ‘excellent’ to ‘poor’. Do take note, cut grade only applies to round shape diamonds. For any fancy shape diamonds, cut quality refers to its symmetry and polish.

At DeRocks, we only stock diamonds that have an excellent or very good cut.


Flawless: No inclusions and no blemishes visible under 10x magnification

Internally Flawless: No inclusions visible under 10x magnification

Some small surface blemishes may be visible under magnification 

Visually ‘eye clean’

Very Very Slightly Included: Inclusions so slight they are difficult for a skilled grader to see under 10x magnification

Visually ‘eye clean’ 

Very Slightly Included: Minor inclusions observed with effort under 10x magnification

Ranges from difficult (VS1) to easy (VS2) to see under magnification

Slightly Included: Inclusions are noticeable at 10x magnification

SI2 inclusions may be visible to the naked eye, especially when viewed from the side

Included: Inclusions are obvious under 10x magnification and are likely to the impact transparency and brilliance of a diamond  

Part of the inherent beauty in diamonds is that they are a rare natural resource and every stone is unique. This means, inevitably, they all contain imperfections. In the diamond world, we call these imperfections “inclusions” and “blemishes”. 

Inclusions are found within the internal structure of the diamond and are due to the intense heat and pressure during a diamond’s formation deep under the Earth’s crust. Blemishes are more external, and are often down to the way the diamond has been handled during and after mining. Therefore, the clarity of a diamond tells you about the extent to which an individual stone has inclusions and blemishes.

The GIA’s clarity scale assigns a clarity grade ranging from flawless (meaning that inclusions and blemishes are invisible to the human eye, or in other words ‘eye clean’) to diamonds with obvious inclusions (meaning these inclusions and blemishes are clearly visible with the human eye). Diamonds with the smallest and least inclusions receive the highest clarity grade, therefore affecting the overall price of a diamond.

The scale above gives some more information and highlights how we only stock diamonds graded FL to VS2.



Near Colourless


Very Light


When talk about diamond colour, what we actually mean is the “lack of colour”.

A diamond with less colour has less structural defects and so it will sparkle more. This is to do with how much they refract light (which is a level of physics that we won’t go into!). People tend to desire diamonds with less colour since they sparkle more and as such, these are more expensive.

The industry standard for grading a diamond’s colour is the GIA’s colour scale. It begins at D (a colourless stone) all the way to Z – each lower grade indicates more colour in the diamond.

At DeRocks, we only stock diamonds in the D-G range.


This illustration depicts the relationship between carat weight and size (mm). Please note that the sizes above are approximate and the size of each diamond will vary slightly depending on the way in which they are cut. Use this as an approximate guide, not to scale.

The “carat” is the standard unit of weight for all gemstones. Each carat is subdivided into 100 ‘points’ which allows for very precise measurements. This means that sometimes, you might hear a diamond below one carat described by its points, rather than by carats. For example, a jeweller might refer to a diamond that weighs 0.20 carats as a ‘twenty pointer’.

Prices of diamonds rise exponentially in relation to its size, thus, larger diamonds are much rarer. In practice, many people refer to the weight of the diamond as the size. As a rule of thumb, 1 carat is 1/5th of a gram (200mg), so 5 carats is equivalent to 1 gram.

The chart above gives some insight into how the weight of a diamond correlates to the size in millimetres.


One might argue that the 4C’s should really be the 4C’s + S. The terms ‘Cut’ and ‘Shape’ are often confused. ‘Cut’ refers to the quality of the craftsmanship that has gone into the diamond, whereas the ‘shape’ refers to the outline of the diamond. The most common shape is round/brilliant and all other variations are considered ‘fancy’.

Shape also has an impact on price. Shapes that are more square tend to be cheaper as less of the diamond’s raw material is lost in the cutting process.

At DeRocks, we stock a wide variety of shapes but focus mainly on round diamonds.

Want to Learn More?

Head over to the GIA website where you can find a comprehensive overview of the 4C’s. 

Better still, come into our office and get a free consultation. There’s nothing like seeing diamonds close up and we always aim to educate our customers so that they can make informed decisions when purchasing their diamonds.