Know Your Diamonds
The Gemological Institute of America (GIA) created the first, and now globally accepted standard for describing diamonds: Colour, Clarity, Cut, and Carat Weight. Today, the 4Cs of Diamond Quality is the universal method for assessing the quality of any diamond, anywhere in the world.
Diamonds come naturally in every colour of the rainbow. However most people are concerned with diamonds in the white range. The Gemological 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.
The clarity of a diamond is determined by the amount and location of flaws, or blemishes, in the diamond when viewed under 10 power (10x) magnification. 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 rare, and therefore valuable.
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, etc.) Every diamond regardless of its shape gets it brilliancy and scintillation 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.
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.