diamonds - the 4cs


The most desirable diamonds are those which 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.

Diamond colour chart

Of the 4 C’s 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 diamonds characteristics (4 C’s) are most valued by your partner

At Irvines Jewellers we have an extensive range of jewellery and gifts to celebrate these very special occasions.

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A diamonds cut is undeniably the most important of the 4 C’s. Even with close to perfect colour, size and clarity if a diamonds 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.

Diamond cut chart

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 which requires some thought is the shape of the diamonds cut. This will come down to personal taste, just be sure that the diamond has a good to excellent cut. The properties of a diamond can be examined by a reputable diamond laboratory although once a diamond has been placed into a setting then this is no longer possible.

Some of the more common shapes and cuts include:

Brilliant diamond
Princess diamond
Oval  diamond
Marquise diamond
Pear diamond
Heart diamond
Emerald diamond
Trilliant diamond
Radiant diamond
Cushion diamond
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The clarity of a diamond is what ultimately makes it unique as no two diamonds have the same markings or inclusions in the same area. The degree in which they are visible is what determines their value, for example a diamond which has no inclusions is rare and will be reflected in the price.

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 can affect clarity grade more so than inclusions found under the side facets
  • The visibility of the inclusions - the darker the inclusions the less favourable the grade will be

The degree of inclusions and the universal method of calculating a diamond’s clarity can be seen in the diagram below. Most inclusions are not visible to the naked eye however under 10x magnification they become apparent.

When purchasing your diamond you should consider the colour and clarity together. A diamond graded D-F would be best if it had a clarity grade of VS2 or higher whereas a diamond in the G-I range is well suited to clarity grades of SI.

Diamond clarity chart
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Carat Weight

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. The higher the carat weight the more valuable and rare the diamond. It is worth noting that a 2ct diamond will be more valuable than two 1ct diamonds as finding larger rough diamonds is not as common.

A diamond will increase in weight much faster than it increases in actual face up diameter. An ideal 1ct will measure approximately 6.5mm in width, whereas a 2ct diamond will measure approximately 8.2mm width. The proportion of weight increase is not proportional to the appearance size increase.

Diamond sizes

When selecting carat weight consider factors such as:

  • Personal preference
  • Finger size
  • Practicality
  • The characteristics of the other diamond elements which will compliment 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 and family for advice.

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