What makes diamonds special?

The most familiar uses of diamonds today are as gemstones used for adornment, and as industrial abrasives for cutting hard materials. The dispersion of white light into colours of the spectrum is the primary characteristic of gem diamonds. In the 20th century, experts in gemology developed methods of grading diamonds. Four characteristics, known informally as the ‘4 Cs’, are now commonly used as the basic descriptors of diamonds.

THE FOUR Cs

The commercial value of a diamond is determined by four characteristics known as the ‘4 Cs’ – carat, colour, cut and clarity.

C1: Carat

The value of a diamond is partly determined by its weight and the price per carat of diamond rises proportionately with size.

A carat is the international unit of measurement used to measure the weight of diamonds. One carat is the equivalent of 0.2 grams.

In the diamond trade, fractions of a carat are referred to as points. One carat is divided into 100 points – so each point is 1/100th of a carat. A 10-point diamond weighs 1/10th of a carat, and a 50-point stone weighs one-half carat.

More weight equals more money so many diamond cutters sacrifice brilliance to maximise carat weight and profit. But, weight does not always equal size or beauty. Poorly cut diamonds, even if they are big, can be dull and lifeless.

The following chart indicates the average mm size per carat:

C2: Colour

Diamonds typically range from pale yellow to colourless, but can also be brown, blue, green, orange, red, pink and black. Colour has a significant impact on the diamond’s appearance as the presence of noticeable colour may reduce its ability to reflect light. Usually, the most valuable diamonds have little to no detectable colour. But, stones with colour called ‘fancy colours’ are very rare and are highly prized.

The most common diamond colour is yellow and the Gemological Institute of America (GIA) Grading Scale for diamond colour is based on the amount of yellow that is visible. Each colour grade is based on a very small range.

C3: Cut

Regardless of the size of the diamond, cut is often considered the most important ‘C’, and is governed by man’s skill rather than by nature. The cut of a diamond is crucial to its ability to reflect light and has the greatest influence on its beauty.

Cut refers to the evenness, symmetry and angle of a diamond’s facets. A master cutter cuts and angles to precise specifications so the diamond optimally reflects the maximum amount of light through the top of the stone giving it sparkle and brilliance. If a diamond is cut too deep, light escapes out of the side and the centre will appear dark, absorbing rather than reflecting light. A very shallow cut results in light escaping through the bottom, causing the diamond to look like a dull piece of glass.

In 1919, Marcel Tolkowsky, a mathematician and gemologist, developed the formula for cutting diamonds to achieve the most brilliance in a diamond. The round brilliant diamond cut has become an industry standard and is known as the ‘American Ideal Cut’ or the ‘Tolkowsky Brilliant’.

C4: Clarity

Because they are formed deep within the earth, under extreme heat and pressure; virtually all diamonds contain ‘birthmarks’; small imperfections inside the diamond (called inclusions), or on its surface (called blemishes). Clarity refers to the degree to which these imperfections are present. Therefore, the fewer imperfections or inclusions within a stone, the rarer and the higher its value.

The clarity scale was developed by the GIA to quantify these imperfections.

All diamonds are systematically graded and plotted under 10X magnification. If a trained grader cannot see a clarity characteristic at 10X, it does not affect the clarity grade.