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Published: 27/11/2017

Gemmologists and jewellers assess the physical attributes of diamonds using the 4 C’s classification system – cut, carat, colour and clarity. The 4 C’s classification enables the comparison and valuation of diamonds. No one ‘C’ is more significant than another, and none will diminish in value over time.

A diamond’s beauty is based on far more than these characteristics. Each one was formed billions of years ago and has travelled a long and arduous journey from deep within the Earth. And while most of a diamonds’ qualities are defined by nature, it takes a master craftsman to unlock the diamond’s true brilliance, fire and beauty.


Carat refers to the weight of a diamond. As with all precious stones, the mass – and therefore the size – of a diamond is expressed in carats.

The carat has an interesting story. Centuries ago, the gem dealers of the Middle East used the seeds of the carob tree (carob became carat) to balance their scales. These seeds were called “keration” (little horn) in Greek, because the pods in which they grew were shaped like horns. These seeds were surprisingly uniform in mass; on ancient scales, the balanced exactly, and even the best modern scales cannot detect more than one three-thousandth of an ounce difference between the seeds. Diamonds were traditionally weighed against these seeds until the system was standardised and one carat was fixed at 0.2 grams (one-fifth of a gram).

A carat is divided into 100 “points” so that a diamond of 75 points is described as a three-quarter of a carat or 0.75 carat (ct.). Since larger diamonds are found less frequently in nature, a single 1-carat diamond will cost significantly more than two 1/2-carat diamonds, assuming the colour, clarity and cut are the same.


Colour refers to the degree to which a diamond is colourless.Diamonds can be found in many colours, however, white-coloured or colourless diamonds remain the most popular and therefore the most expensive. It sometimes surprises people to learn that diamonds can cover the entire spectrum of colours. The majority, however, range from those with a barely perceptive yellow or brownish tint, up to those that are very rare and are described as colourless. Some even rarer stones are naturally coloured and are referred to as “Coloured Fancies”. These diamonds are only found very occasionally and can come in tints such as green, pink, red, blue and amber. Red is the rarest of all. Coloured fancies are extremely rare and highly treasured.When we speak of colour in diamonds, most people think of the beautiful reds, blues, and yellows we see when a diamond flashes in the sunlight. In fact, grading a diamond for colour means deciding how much the diamond’s “body colour” deviates from the whitest possible (water like colourless) colour. Nature provides a continuous darkening in the tints from white to yellow, white to brown, and white to green. Divisions are determined by the ability of the human eye to separate one tint from an adjacent one that is slightly lighter or darker. This concept should not be confused with the sparkle, brilliance, or scintillation of the diamond.

Diamonds are graded on a colour scale which ranges from D (colourless) to Z. Warmer coloured diamonds (K–Z) are particularly desirable when set in yellow gold. Icy winter white coloured diamonds (D–J) look stunning set in white gold, platinum or palladium. Colour differences are very subtle and it is very difficult to see the difference between an E and an F, for example. Therefore, colours are graded under controlled lighting conditions and are compared to a master set for accuracy. Truly colourless stones, graded D are treasured for their rarity. Colour, however, is subjective. The Incomparable, one of the world’s most beautiful diamonds, contains hints of brown, smokey amber and champagne colours.

Because of the diamond’s high brilliance and dispersion of light, the colour grade cannot be accurately determined by looking at the stone from the top (face up) position. It is best to observe colour by examining the stone through the side of the pavilion (bottom of the stone) with the diamond upside down in a white paper grading through. Please note in the illustration below the stone can be examined in several positions to obtain an accurate colour grade.


Grading diamonds for clarity is the process of classifying the imperfections, both internal and external. Imperfections are called inclusions when internal and blemishes when external. The term clarity is preferred over purity because purity has a very narrow definition pure or impure. In order to accurately classify clarity in polished diamonds, we need to have several levels of clarity.

FL-Flawless– These stones have no imperfections inside or on the outside of the stone under the magnification of a loupe of 10X magnification.

IF-Internally Flawless – This grade is awarded to diamonds with no internal flaws and only minor external blemishes. Nicks pits or girdle roughness, not on the table, which could be removed in re-polishing.

VVS1, VVS2 – Very Very Slightly Imperfect – These stones have very, very small inclusions, which are extremely difficult to see under a loupe of 10X magnification.

VS1, VS2 – Very Slightly Imperfect – These stones have very small inclusions, which are slightly difficult to see under a loupe of 10X magnification.

SI1, SI2-Slightly Imperfect – These stones have inclusions, which are fairly easy to see under with a 10X magnification, and can be seen with the naked eye.

I1, I2, and I3-Imperfect – These stones have inclusions ranging from eye visible to very easily seen to the naked eye.


Cut refers to the angles and proportions of a diamond, not the shape. It is the only one of the 4C’s that is influenced by the human hand. Diamond cutting requires great skill and training. The cutter must polish tiny surfaces known as facets onto the rough diamond. This process is what creates the facets known as the crown, culet, table, girdle and pavilion of the diamond.

To cut a diamond perfectly, a craftsman will often need to cut away more than 50% of the rough diamond. The better a diamond is cut, the more light it will reflect, with the result that the diamond has more brilliance. This means that there are good and bad cuts in every shape.

As shown in the images below, when a diamond is well-cut, light enters through the table and travels to the pavilion where it reflects from one side to the other before reflecting back out of the diamond through the table and to the observer’s eye. This light is the brilliance we mentioned, and it’s this flashing, fiery effect that makes diamonds so mesmerizing.

In a poorly cut diamond, the light that enters through the table reaches the facets and then ‘leaks’ out from the sides or bottom of the diamond rather than reflecting back to the eye. Less light reflected back to the eye means less a brilliant and less valuable stone. A well-cut diamond is therefore higher in quality and value than deep or shallow-cut diamonds.


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