THE 4CS OF A DIAMOND
The 4Cs are colour, clarity, cut and colour which together, make up the grading system that determines the rarity of a diamond.
Prior to the development of the 4Cs, there was no agreed-upon standard by which diamonds could be evaluated. In the 1940s, the founder of the GIA coined the term 4Cs to characterise a diamond. It was revolutionary and has become the international standard of grading diamonds to determine diamond quality.
COLOUR
Diamond colour is graded in terms of how colourless a diamond is.
The GIA and the IGI grades diamonds from D to Z, with D being the most colourless and Z having a noticeably brown or yellow colour, which is caused by the presence of nitrogen.
Past the colour grade Z, you then enter into the world of fancy colour diamonds which are graded distinctly from traditional colourless diamonds.
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Whilst the naked eye generally cannot tell the difference between two adjacent colour graded diamonds, the price difference between the two can be significant.
Very Light
Fact: Prior to the GIA's colour system, there were many different colour systems which included using letters of the alphabet (such as A, AA, AAA etc). Because of this, the grading system starts at D, rather than A, to avoid confusion.
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CLARITY
The clarity of a diamond measures the absence of blemishes and inclusions in a diamond. The fewer the blemishes and inclusions, the higher the clarity grade. Inclusions are largely crystals of diamond or a foreign material that has formed within the stone affecting the internal composition, while blemishes are flaws which affect the stone's surface.
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To help, the GIA and IGI have clarity scales which range from Included ("I") to Flawless ("FL") (for GIA) and Internally Flawless ("IF") (for IGI).
Clarity is determined by noting the size, number, position, relief (which is how visible the inclusion is in contrast to the stone) and type of inclusions or blemishes present in a diamond when it is face up and how easily they can be seen under a microscope with a 10x magnification.
CUT
The diamond cut grading refers to how well it has been cut and polished and its symmetry. It is often said to the most important of the 4Cs as cut quality directly impacts a diamond's brilliance (the flashes of white light) and fire (the dispersion of the white light into rainbow colours). Sometimes you may here of a diamond shape referring to its cut (e.g. princess cut, emerald cut), but diamond cut does not refer to a diamond's shape.
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The GIA's cutting grades range from Excellent to Poor.
The IGI's cutting grades range from Ideal to Fair.
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As diamond cut has such a great impact on a diamond's beauty and brilliance, we recommend selecting a diamond with the highest possible cutting grade. At the highest cutting grade, all incoming light is reflected through the table (the top flat part) of a diamond.
CARAT
The carat of a diamond is often misunderstood as referring to its size when, in fact, it refers to a diamond's weight. Specifically, one carat is equal to 0.2 grams (or referred to as 100 points).
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As diamond carat refers to weight rather than size, it is possible to have a diamond of lower carat weight than another, but have similar dimensions, appearing to look the same size.
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Fact: the word carat originates from "carob" which is a locust tree that produces edible pods. Carob seeds, being even in weight, were used as weighing references by traders in ancient times.
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