This relates to the marks of non-crystallised carbon called ‘inclusions’ found within the diamond. The inclusions vary in standards on the spectrum ranging from FL (flawless), SI1 to I3. 

It is exceedingly rare for a diamond to be flawless, known as FL and is the highest level on the spectrum. SI1 is in the middle of the spectrum and it is recommended when buying a diamond that you should not purchase lower than this standard. I3 is the lowest as it includes the most inclusions and is least clear. 

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 affects clarity grade more so than inclusions found under the side facets.The visibility of the inclusions – the more visible the inclusions to the naked eye the less favourable the grade will be.

Diamonds come in every colour; however, coloured stones are less desired as it diminishes it’s ability to refract light in the same way as colourless diamonds. This holds true unless the coloured diamonds are ‘Fancies’- these are rare diamonds of unusually strong colour.The grade used to determine the desirability of colour in a diamond is measured from D (colourless) to Z (coloured yellow). The clear diamonds are the most prized and are the most expensive. It is recommended while purchasing a diamond you do not choose one less than grade H.

The method of measuring a diamond is by its weight or carat. One carat is 0.2 grams and can be further divided into 100 points (this is the method used to determine the lower carat stones). In other words, the smaller the stone the lower in carat weight, whereas, the larger the stone the higher the carat and price.

Ensure that you receive a certificate when buying diamonds. There are a few highly reputable grading houses around the world and they include GIA, AGS and DCLA. Never accept the certificate of the retailer, even if they are GIA certified. Only accept certificates from the above-mentioned graders as they maintain high standards and ensure that the quality of the stone is exactly what you have paid for. Other labs are pressured to lower their standards; therefore you will be paying for a lower quality stone for a higher price.