The Four Cs

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Every diamond has distinguishable characteristics. At Ryan Thomas Jewellers, our diamonds are bright and brilliant because we only choose those of the highest quality. Their superior quality is determined by the 4Cs; cut, colour, clarity and carat weight.

The 4Cs of diamond quality is the universal method for assessing the quality of any diamond, anywhere in the world.


The cut refers to how well a diamond’s facets interact with light. More than any other factor it is responsible for the beauty of the diamond. The cut is determined by three factors; the proportion, symmetry and polish. When a diamond is cut to exact proportions, light will reflect from one facet to another and disperse through the top of the stone, resulting in a display of brilliance and fire.

Diamonds that are cut too deep or too shallow lose light as it spills through the side or bottom. So if a diamond is cut poorly, it will appear dull even if it has a high colour and clarity grade. Skilled workmanship is essential to cut a diamond so its proportion, symmetry and polish deliver maximum brightness and sparkle.


While most diamonds appear white, many of them display hints of colour. The closer a diamond approaches colourless, the rarer and more valuable the stone. Colour grading starts at 'D' (‘D’ is the highest grade- there is no ‘A’ grade!) and continues through to ‘Z'.

Ryan Thomas Jewellers only accepts diamonds in the “colourless” and “near colourless” range on a diamond colour scale. In other words, we accept D colour diamonds, E colour diamonds, F colour diamonds, G colour diamonds and H colour diamonds.

This means that all of our diamonds are bright white and sparkle greatly, whereas diamonds with a poor colour grade can appear yellow.


Diamond clarity refers to the absence of inclusions and blemishes in the stone.

A diamond with a poor clarity grade has multiple inclusions. As the size and position of these inclusions affect the refraction of light, the diamond will appear dull and cloudy.

Since an inclusion is an internal flaw, diamonds are graded on a Clarity Scale ranging from ‘Flawless’ (FL) to ‘Included’ (I). Ryan Thomas Jewellers rejects any diamond that has a poor clarity grade.


The carat refers to the weight of the diamond. One carat is equal to 200 milligrams. Each carat is subdivided into 100 points, allowing very precise measurements.

Therefore, a diamond that weighs less than a carat may be described by its points. For example a solitaire diamond ring with a .50 carat diamond can be described as having a carat weight of 50 points.

Diamonds weighing greater than 1 carat are expressed in decimal points. For example a 1.80ct solitaire diamond ring.

Larger diamonds are more rare and valuable, however two diamonds of equal carat weight can have two very different values, since the value of a diamond is determined by all of the 4cs, not just the carat weight.