Diamond Quality Guide

This diamond quality guide gives an insight into the 4 Cs of diamond grading: colour, clarity, cut, and carat weight. When searching for a diamond ring, engagement ring, wedding ring, earrings or any other piece of diamond jewellery, it is important to understand the 4 Cs. Our guide features an explanation of grades allocated to certified diamonds, and which grades signigy a diamond of exceptional quality.

Initiated by the GIA in the 1950s, the 4 Cs of diamond grading provide the jewellery industry with a systematic and transparent way to present their diamond jewellery. The 4 Cs can be seen as quality factors that are accompanied with all certified diamonds and give the consumer an understanding of the type of diamond they are looking at.


The cut grade assesses the quality of a diamond’s facet arrangement. The GIA and other diamond laboratories only award round brilliant cut diamonds with a cut grading. Cut is judged from excellent to poor, and takes into account the symmetry of the stone, the proportions and the polish of the stone.

The better the cut grade, the better the optical effects of the diamond and therefore the higher quality it is. When purchasing a diamond, it is highly important to buy one with the best cut grade possible, as this affects the fire, brilliance and scintillation of the stone.


The clarity grading of a diamond is an indication of how ‘clean’ the stone is. The clarity grades run from flawless to imperfect or included. The clarity grade assesses the diamond’s freedom from inclusions and blemishes.

GIA Diamond Clarity Scale

Inclusions are natural imperfections within the diamond that form whilst the crystal is growing. They can range from tiny pinpoint inclusions to crystals of other gem materials such as garnet or chrome diopside! Inclusions can vary in their visibility levels, diamonds with clarity gradings higher up the scale will have no inclusions or ones that are incredibly hard to see with 10x magnification. Those on the lower end of the scale have imperfections that can be easily seen with the naked eye.

Blemishes are external characteristics of the diamond. These external features can include grain lines, additional facets, scratches, polishing lines, and burn marks.

The higher the clarity grade, the higher quality the diamond is. Inclusions can affect the beauty, but also, in extreme cases, the durability of the diamond so it is important to carefully consider the clarity grade of any stone you purchase.


Colour is another factor that dictates the quality of a diamond. Colour is graded on a scale from colourless to tinted, D to Z. D is the highest colour grade awarded, and diamonds that are entirely colourless are incredibly rare.

GIA Diamond Colour Scale

Most diamonds are coloured by trace elements within their crystal lattice. Nitrogen is an element that is present in the majority of diamonds and this gives them a yellow tone. The more colourless the diamond, the purer and more rare it is perceived to be. However, the differences between the grades at the top end of the scale are barely perceptible to the unaided eye, and colour preference is entirely in the eye of the beholder.

Carat Weight

The carat weight is an indication of the size of the diamond. One carat is equivalent to 0.2 grams. Each carat is split into 100 points, and so a 0.50ct diamond is also known as ‘fifty points.’

Larger diamonds of a high quality are rare and highly sought after. However, there are ‘magic’ sizes that attract a higher price. For example, a 1.01ct diamond will be worth up to 20% more than a 0.98ct diamond, all other factors being equal. Although the difference in the appearance of the two stones will be barely perceptible, the importance placed upon having a 1ct diamond by popular culture gives the stones over the ‘magic’ 1ct weight a premium.

In terms of diamond quality, the standard of the other 3 Cs are more important than carat weight. Large diamonds of an exceptional colour and clarity are rare, but large stones of a poor quality are not! It is important to find a diamond with a good cut, clarity and colour to ensure that your diamond displays the very best brilliance, fire and scintillation.

The British Diamond Company selects and supplies the finest quality, ethically sourced, certified diamonds. Browse our range of stunning diamond set jewellery that has been crafted at our Derbyshire workshop. Order today for 0% interest free finance and free UK delivery.

For further information and advice on how to choose the perfect diamond for you, contact our team of experts who will be happy to help. Call us on 01335 453 453 or email us sales@britishdiamondcompany.com.