the 4 C's

The 4 C's were devised in the late 1930 as a way to describe a diamond's characteristics consistency and clarity, and became a language that crossed borders. Now, anyone trading in diamonds from anywhere in the world will understand and use the 4 C's.


The weight of the diamond. A one carat diamond will weight approximately 0.2g in physical weight.
This is not to be mistaken with the size or measurements of the diamond. Different shapes of diamonds and even different diamonds of the same shape will measure differently even though the carat may be the same.

Here at IGR we measure the carat of your diamond using a highly sensitive scale giving us the weight to 3 decimal places to ensure accuracy. We check before placing each stone onto the scales that the scales are calibrated to ensure the upmost accuracy.


The clarity of a diamond refer's to it’s lack of imperfections. The cleaner a diamond, the rarer it is and therefore more valuable it is. A clarity grade is given based upon the type, size, placement and abundance of imperfections in the diamond. The chart below will explain the boundaries from one grade to another.

We grade clarity using a 10x triplet loupe and our eyes. Our qualified and experienced graders can identify imperfections and grade based on what they see. Our graders will also use where required a 40x microscope with various light settings. This will allow us to investigate a diamond further with regards to the nature of any imperfections, or detecting treatments.


Diamond colour is graded according to how much or little yellow/brown/grey colour a diamond has. Also taken into account is the saturation and tone of the colour where seen. The colour grading scale ranges from D to Z, where D is colourless (the rarest) and Z is extremely yellow. The chart below will illustrate the breakdown of each grade into sub sections.
At IGR we grade the colour of your diamond using a technique which is accepted as the only way to grade colour in the industry. We use a daylight lamp (as others will influence the colour seen in the diamond), a darkened environment and a white colour grading card. The white card will highlight any colour in the diamond at all. We also use a “master set”. This is a set of diamonds that are carefully chosen to represent “true” colours.

There is not currently a machine that will grade colour as accurately as the human eye.


This characteristic is determined only by the skill and expertise of the diamond artisan who takes a diamond on the journey from rough to polished and ready for your jewellery. The cut grading will provide you with a grading based upon the diamond’s symmetry and polish, and with round brilliant diamonds only a separate factor known as the cut. The cut for a round brilliant diamond will refer to the proportions of the diamond, ensuring all facets are placed correctly and at the correct angles for maximum light refraction.

Polish will be graded by eye and by magnification in a process similar to clarity grading to detect polishing lines caused during the fashioning of the diamond. The less polish lines the better.

Symmetry is graded by eye and also by machine. Both together will provide an accurate grading on how symmetrical the diamond is. The machinery used is state of the art within the industry and will inspect the entire diamond carefully for any anomaly.

Cut grading for round diamonds is a more technical process as the angles and placement of every single facet must be taken into account. This process uses the latest technology as described with symmetry grading. Each and every surface of the diamond is mapped digitally for our inspection and grading.