When you are considering buying or selling a diamond, it is important to understand the basics that the diamond trade use to grade a diamond - often referred to as 'the 4 'C's
4. Carat weight
1. Diamond CUT
When we speak of ‘cut’ we are more interested in the proportions of the diamond as opposed to its shape (Round Brilliant, Marquise, Pear, Princess-cut, etc.)
Every diamond regardless of its shape gets it brilliancy and ‘sparkle’ by cutting and polishing the diamond facets to allow the maximum amount of light that enters through its top to be reflected and dispersed back through its top.
A correctly cut diamond where the angles are correct allows the light that enters to be dispersed properly back through the diamond's top facets. When a stone is cut too shallow, or too deep , the light that enters through the top is allowed to escape through the diamond's bottom and does not allow the maximum beauty of the diamond to be realized.
‘Cut’ is widely regarded as the most important factor to consider when choosing a diamond.
2. Diamond CLARITY
The clarity of a diamond is determined by the amount and location of naturally occuring flaws, or blemishes, in the diamond when viewed under 10 power (10x) magnification.
GIA rates clarity grades in diamonds from Flawless to Imperfect 3.
Most diamonds contain very tiny birthmarks known as "inclusions." An inclusion can interfere with the light passing through the diamond.
The fewer the inclusions, the more beautiful the diamond will be
Diamonds have the capability of producing more brilliance than any other gemstone. A diamond that is free of inclusions and surface blemishes is very rare…and therefore very valuable.
3. Diamond COLOUR
Diamonds come naturally in every colour of the rainbow. However, most people are concerned with diamonds in the white range. The Gemmological Institute of America (GIA) rates the body colour in white diamonds from D (colourless) to Z (light yellow).
The best colour for a diamond is no colour at all. A totally colourless diamond allows light to pass through it easily, resulting in the light being dispersed as the colour of the rainbow.
Colours are graded totally colourless to light yellow. The differences from one grade to the other are very subtle and it takes a trained eye and years of experience to colour grade a diamond
4. Diamond CARAT WEIGHT
This is the weight of a diamond measured in carats. As the carat weight of a diamond increases so does its rarity and therefore its price.
One carat is divided into 100 "points," so that a diamond of 75 points weights .75 carats.
The carat-weight of a diamond is the easiest measurement to determine.
Most importantly, two diamonds can be of equal carat-weight, but their value can differ greatly due to their cut, colour, and clarity