Diamond Grading - The 4 C's

When purchasing a diamond, it is essential to know its grading, as it represents its characteristics. The four most important properties are the 4Cs: Cut, Colour, Clarity, and Carat Weight.

Cut

Cut is probably the most important and most challenging of the 4Cs to understand. A diamond's brilliance depends significantly on its cut. A cut does not refer to the shape of the diamond. Rather, it refers to 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 at a diamond, while 'brilliance' refers to the sparkle.

The best proportionate round diamonds, with perfect angles, become the most beautiful diamonds, designated as 'Hearts and Arrows' (refer to our article on Hearts and Arrows).

Hearts and Arrows are even better than excellent-cut diamonds. This diamond commands a premium price in the market. These diamonds are graded with extra specifications and are not included in the regular cut criteria.

Colour

Though a colourless diamond is considered most valuable, diamonds have some degree of colour. 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 grey 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 noticeable 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, the yellower the stone, the less value it has. There's a good reason behind it. As a diamond goes more yellow, the sharpness decreases and becomes dull. A whiter stone allows greater light to pass, sparkling and shining.

Except for a few natural fancy colours like blue, pink, purple, or red, the more natural a diamond is, the less it is worth compared to its colourless counterpart. Opaque diamonds, such as black diamonds, are much less expensive than clear white diamonds.

Clarity

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 visible under a loupe's magnification. The fewer the inclusions, the more transparent, brilliant, and expensive the diamond. A flawless diamond has no inclusions and is extremely rare and valuable.

A diamond, with fewer inclusions, is rarer and more desired, making it more expensive. A diamond with a purity of IF to VS2 will sparkle greatly, whereas diamonds ranging between SI1 and SI2 will only sparkle. Diamonds between I1 and I3 will lack any sparkle and life, and their 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 categorised 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 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 minor blemishes. Very Rare.
• VVS1 - VVS2  Very-Very Slightly Included, Inclusions are so slight that they are difficult for a skilled grader to see under 10x magnification, an excellent quality diamond.
• VS1 - VS2 Very Slightly Included. Minor inclusions can be characterised with effort under 10x magnification. This is an excellent-quality diamond.
• SI1 - SI2 Slightly Included. Inclusions are noticeable under 10x magnification and may not be visible to the naked eye when the stone is in the face-up position. This is a very good-quality diamond.
• I1 - I3 - Inclusions are noticeable under 10x magnification, which may affect transparency and brilliance, and command a low price.

It is also important to note that while two stones may have the same clarity grade, one may have more inclusions that are more visible to the naked eye than the other due to the position of the inclusions.

Carat-Weight

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 exact 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.