A diamonds cut is undeniably the most important of the 4 Cs. Even with close to perfect colour, size and clarity if a diamond’s cut is not in correct proportions all other characteristics will not be as highly valued. The way in which a diamond is cut will determine how the diamond reflects light and hence determine its brilliance or sparkle. A poorly cut diamond will appear lifeless and dull.

Diamonds reflect their light from one facet to the other. If the cut of the diamond is too deep then light will escape through the opposite side of the pavilion. On the other hand if the cut is too shallow then light will escape through the pavilion before it can be reflected.

The other consideration that requires some thought is the shape of the diamond’s cut. This will come down to personal taste, but be sure that the diamond has a good to excellent cut. A reputable diamond laboratory can examine the properties of a diamond, although once a diamond has been placed into a setting then this is no longer possible.

People often confuse ‘cut’ with a diamond’s shape and the two refer to different aspects of the stone. Cut relates to how the rough diamond has been cut to maximise diamond weight among other qualities whereas shape relates to the physical appearance of the diamond.

This relates to the marks of non-crystallised carbon called ‘inclusions’ found within the diamond.

Inclusions vary from flawless (FL) to imperfect (I3) with a number of grades in between the two extremes. Flawless diamonds are exceedingly rare and are best suited to diamonds that have a colourless grade (typically D-F range). A clarity grade of I3 which means that the diamond has inclusions which may be visible to the naked eye are best suited to lower colour grades as the inclusions won’t be as evident.

The clarity grade is determined by several factors including:

• The size of inclusions.

• How many inclusions.

• The positioning of the inclusions - inclusions found under the table affects clarity grade more so than inclusions found under the side facets.

• The visibility of the inclusions – the more visible the inclusions to the naked eye the less favourable the grade will be.

The most desirable diamonds are those that have the least amount of colour. Quite often however diamonds will have a tint of yellow or brown. Generally, diamond colour can be divided into four categories.

Of the 4 Cs colour can be the most confusing to understand. It’s not until you get to the I-J range and onwards that you start noticing hints of colour and even so it depends on how you are viewing the diamond. When viewed face up the diamond will appear perfectly white however when viewed face down against a completely white background you will be able to detect the colour much more easily. Near colourless diamonds are more common and offer great value for money.

The price difference between the various colour grades can be significant so to help you make the right choice you should really find out which of the diamond characteristics (4 Cs) are most valued by your partner.

Of course diamonds come in a range of colours however coloured diamonds (such as pinks, blues and yellows) are typically referred to as ‘fancies’.

A diamonds weight is measured in carats and is the easiest of the 4 Cs to measure. A carat is equal to 100 points or approximately 0.2 grams.

A diamond will increase in weight much faster than it increases in actual face up diameter. An ideal 1.00ct will measure approximately 6.5mm in width, whereas a 2.00ct diamond will measure approximately 8.2mm width. The proportion of weight increase is not proportional to the appearance size increase.

When selecting carat weight consider factors such as:

• Personal preference;

• Finger size;

• Practicality; and

The characteristics of the other diamond elements which will complement the size of the diamond.

Ultimately the diamond you purchase should be chosen based on personal style and budget. If the diamond is being purchased as an engagement ring then try and gain an understanding of what your partner likes and even ask friends or family for advice. Or, if you’re like a growing number of couples, you may find yourselves making the decision jointly.