How Are Diamonds Graded?
When looking to purchase a diamond, it is important to know the grading, as they represent the characteristics of that diamond. The four most important properties are known as the 4C’s. These are the Cut, Colour, Clarity and Carat Weight.
Cut is probably the most important and most challenging of the 4Cs to understand. The brilliance of a diamond depends significantly on its cut. A cut does not refer to the shape of the diamond. Rather, it refers to the the quality of the proportion of the angles with which the diamonds are cut to perfection. When a diamond is cut to ‘Excellent’ or ‘Very Good’ proportions, light is reflected from one facet to another and is dispersed through the top of the diamond, resulting in a burst of fire and brilliance. ‘Fire’ is a term for the flashes of colour one sees when you look at a diamond, while ‘brilliance’ refers to the sparkle.
The best proportionate round diamonds, with perfect angles, become the most beautiful diamonds and are designated as ‘Hearts and Arrows’ diamonds (refer to our article on Hearts & Arrows in the Twinkle Diamond Blog). H & A are even better than the excellent cut diamonds. H & A cut commands a premium price in the market. H & A diamonds are graded with extra specification and are not included in the regular cut criteria. Click here for more information on Hearts & Arrows.
Though a colourless diamond is considered most valuable, diamonds do have some degree of colour in them. A colour scale established by GIA (Gemological Institute of America) assigns a letter to the degree of colourlessness found in a diamond. Beginning with D and ending with Z, each descending letter denotes an increasing amount of light yellow, brown or gray in the diamonds.
D E F – The stone appears colourless, however a gemmologist can identify the minute traces of colour found in these diamonds.
G H I – These diamonds have a hint of colour that is not noticeable to the untrained eye, almost colourless.
J K L – Faint traces of colour are visible when the diamond is looked at face up.
M to Q – These diamonds have light traces of colour.
R to Z – The colour in the diamond is obvious even to the untrained eye.
Although colours typically bring things to life, in diamonds, the opposite applies. Colourless diamonds are in greater demand than the ones available in the shades of yellow. The rule of thumb is – the whiter the diamond, the better it is.
The yellow colour in diamonds comes from the traces of nitrogen found in them. One part in a million will cause a yellow tint to appear in the colour of diamonds. As a rule, yellow the stone, lesser the value it has. There’s a good reason behind it. As a diamond goes more yellow, the sharpness decreases and it becomes more dull. A whiter stone allows greater amounts of light to pass through it, making it sparkle and shine. With the exception of a few natural fancy colours like blue, pink, purple or red, the more natural colour a diamond has, the lesser it is worth compared to its counterpart colourless diamonds. Opaque diamonds such as black diamonds go for a much smaller price than clear white diamonds.
The clarity of a diamond is based on the number, location, size and type of inclusions found in the stone. An inclusion is an imperfection or trace mineral in the stone that is visible under the magnification of a loupe. The fewer the inclusions, the clearer, brilliant and expensive the diamond will be. A flawless diamond is the one that has no inclusions and is extremely rare and valuable.
A diamond, with fewer inclusions, is both rare and more desired which also makes it more expensive. A diamond with a purity of IF to VS2 will sparkle with great intensity whereas diamonds with a purity ranging between SI1 and SI2 will only sparkle. Diamonds between I1 and I3 will lack any sparkle and life and its inclusions will be noticeable to the naked eye. All other conditions being constant, the lesser the inclusions, greater the sparkle of a diamond, thus the more will one pay for it.
It is almost impossible to have a diamond without impurities. Often invisible to the naked eye, these natural blemishes are categorized as inclusions, which are internal and blemishes, which are external.
While fewer such impurities will make the diamond more valuable, higher quality does not necessarily mean that the diamond is more beautiful than a stone of a lesser clarity, you have to keep in mind the cut quality of the diamonds in question, however it will make a difference in terms of how the diamond is priced.
GIA has established a grading system to measure the type and size of these imperfections.
Fl – Flawless, No inclusions and no blemishes visible under 10x magnification. Extremely rare and expensive.
IF – Internally Flawless, No inclusions visible under 10x magnification, though there may be some minor blemishes. Very Rare.
VVS1 – VVS2 – Very Very Slightly Included, Inclusions so slight they are difficult for a skilled grader to see under 10x magnification, an excellent quality diamond.
VS1 – VS2 – Very Slightly Included, Inclusions are observed with effort under 10x magnification, but can be characterized as minor. An excellent quality diamond.
SI1 – SI2 – Slightly Included, Inclusions are noticeable under 10x magnification, may not be visible to the naked eye when the stone is in the face up position. Very good quality diamond.
I1 – I3 – Inclusions, Inclusions are obvious under 10x magnification which may affect transparency and brilliance, commands a low price.
It is also important to note that while two stones may have the same clarity grade, one may have more inclusions more visible to the naked eye than the other due to the position of the inclusions.
Diamond carat-weight is the measurement of how much a diamond weighs. A “carat” is defined as 200 milligrams. Each carat can be subdivided into 100 points. This allows very precise measurements to the hundredth decimal place. A jeweller may describe the weight of a diamond below one carat by its points alone. The weight of a ¾ carat diamond can be shown as either 0.75 carat or 75 points.