Understanding the basics

In the 1950s the Gemological Institute of America (GIA) created a common language to describe a diamond’s characteristics and developed accurate methods to grade a diamond. The GIA diamond grading system has since become the universal standard and is the most widely accepted Diamond Grading Laboratory in the diamond market today.


A diamond’s colour grade refers to the degree to which the diamond is colourless. Truly colourless diamonds are very rare and consequently come with a higher value in comparison to diamonds with visible colour. Many of these colour differences are subtle to the untrained eye however can make a substantial difference to the quality and price of a diamond


A diamond’s clarity grade refers to the degree to which the diamond is pure. Diamonds form under intense heat and pressure deep in the earth which can cause a variety of internal and external characteristics in the stone called ‘inclusions’ or ‘blemishes’.  The number, size and position of these characteristics determine which clarity grade the diamond will fall into. It is important to remember that while no diamond is perfectly pure, a diamond with fewer inclusions will have a higher value.


The beauty of a diamond depends more on cut than any other factor, and refers to how well the diamond interacts with light. The depth of the diamond is measured from the girdle to the culet and it is this depth that determines how well the diamond can reflect light. A diamond that is too deep or too shallow will allow light to escape from the sides or the bottom of the stone. A well cut diamond will reflect light back out through the crown. A diamond’s cut grade is crucial when evaluating the overall quality of the stone. A diamond can be graded with a high colour and clarity grading but without the craftsmanship of a well cut diamond it will lack any fire and brilliance.


The easiest of the 4Cs to measure, a diamond’s carat weight refers to how much a diamond weighs. It’s important to remember that the weight of a diamond does not always translate into how ‘big’ a diamond looks. A diamond that is cut too deep will look small as the majority of the carat ‘weight’ is underneath the diamond. Therefore, a diamond’s value is determined by a combination of all the 4Cs.