The cut of a stone is not relating to the shape but refers to the way the cutter has formed it to best ensure that light bounces within the stone and back out through the top. If it has a defective cut -too long or too short- the light refracts on the inside and falls out down the bottom. This decreases the brightness and lustre of the stone. A well cut stone is neither exceedingly long nor shallow, it is luminous and will always dazzle when dirty.
The grading system varies from Ideal Cut to Good and lastly, Poor Cut. With round diamonds, it is suggested to never purchase below ‘Very Good’ and ‘Good’ in all other shapes. Again, the better cut stone the more it will cost.
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.
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.