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Find out More About the Four C’s of Diamond Grading

The Four C’s

The Gemological Institute of America (GIA) created the first (and now globally accepted) standard for grading diamonds. This universal method assesses diamond colour, clarity, cut and carat weight – it is commonly referred to as the ‘Four C’s’.



Image credit: GIA

The beauty of diamonds comes from their ability to transmit light and sparkle brilliantly. A diamond’s cut grade isn’t the shape of the diamond – it’s how well a diamond’s facets interact with light. To deliver the most brilliant return of light, precise workmanship is required to fashion the stone so that its proportions, symmetry and polish interact perfectly. When a diamond’s cut is too shallow or too deep, the light that enters through the top escapes through the bottom and does not allow for maximum beauty.



Image credit: GIA

Diamond’s occur in many colours – however, most people are interested in diamonds within the white (transparent) range. The GIA rates the body colour of white diamonds from D (colourless) to Z (light yellow). People favour colourless diamonds because light passes through them easily and is dispersed as the colours of the rainbow. A pure and structurally perfect diamond has no hue (it is the colour of a drop of water).

The GIA’s D-Z grading system measures the degree of colour by comparing a stone under controlled lighting and precise conditions to master stones of established colour value. Many of these colour distinctions are so subtle that they would be unnoticeable to an untrained eye – but they make a huge difference when it comes to diamond quality and price.



Image credit: GIA

Diamond clarity is determined by the amount and location of external blemishes and internal flaws (or ‘inclusions’) in the diamond when viewed under 10x magnification. The GIA system rates clarity grades from ‘Flawless’ to ‘Imperfect’. The fewer internal and external flaws, the more brilliant the diamond. Evaluating diamond clarity involves determining the number, size, relief, nature, and position of these flaws, as well as how these affect the overall appearance of the stone. No diamond is perfectly pure – but the closer it comes, the higher its value.


Carat Weight

Four C's of Diamond Grading-blog-5-weight

Image credit: GIA

The weight of diamonds is measured in carats. As the carat weight increases, so does the rarity (and therefore the price). A metric “carat” is defined as 200 milligrams, and each carat is also subdivided into 100 ‘points’ (for example, a diamond of 75 points weighs .75 carats), as this allows very precise measurements to the hundredth decimal place. It’s important to note that two diamonds can be of equal carat-weight but vary in price due to their cut, colour, and clarity.


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