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The Four C's

Diamond characteristics – Carat

The size of a diamond is measured in carat weight. One carat is equivalent to a fifth of a gram, or exactly 200 milligrams. Each diamond carat is also equal to 100 points; therefore a diamond that is a 1/2 carat can also be referred to as a 50-point diamond. The value of a diamond increases exponentially in relation to carat-weight, with sharp jumps around milestone carat weights, so that a 1.05-carat diamond will be significantly more expensive than a comparable 0.95-carat stone. Poorer quality diamonds tend to be cut to increase their carat-weight and therefore their price, but will not in fact have as much brilliance as a better-cut, lower carat diamond. Carats are also used to measure gemstones other than diamonds.

Total carat weight (t.c.w.) is a phrase used to describe the total mass of diamonds and other stones in a piece of fine jewellery, where more than one gemstone is used. Diamond solitaire earrings, like the Flora Astor ones in the Astley Clarke range, for example, are quoted in t.c.w, indicating the mass of the gemstones in both earrings.

To create a single, one-carat diamond, on average nearly 250 tons of ore must be mined – this explains part of the reason why diamonds are so treasured and expensive.

Diamond characteristics – Cut

The shape of a diamond is commonly confused with the cut, but the two are in fact distinct. The cut refers to the number and angles of the facets. This determines how much light a diamond reflects. A diamond-cutter always attempts to cut a diamond to make the best use of light. When a diamond is well-cut, light is refracted successfully from one facet to another and dispersed through the top of the diamond. If it is cut too deep, some light escapes through the opposite side of the diamond, while if it is cut too shallow, light escapes through the bottom of the stone before it can be reflected. A well-cut diamond has the greatest brilliance, scintillation and fire and therefore looks the most attractive.

The technique for cutting diamonds have been developed over hundreds of years, with the greatest innovations made in 1919 by the mathematician and gem enthusiast Marcel Tolkowsky. He developed the round brilliant cut by calculating the exact shape which return and scatter the most light when the diamond is viewed from above. A diamond cut to his specifications has 57 facets (polished faces), with 33 on the crown (the top half) and 24 on the pavilion (the lower half).

New diamond cuts are constantly being invented. One introduced in 2003 is called the Genesis cut and features concave surfaces and angles, and resembles a 4-pointed star.

Diamond characteristics – Colour

This is the natural body colour visible in a diamond and is the one C determined completely by nature, not by man. Generally speaking, the closer a diamond is to being totally colourless, and therefore chemically pure and structurally perfect, the more valuable and beautiful it is. The most common impurity found in diamonds is nitrogen – this replaces a small proportion of carbon atoms in a diamond’s structure and causes a yellowish to brownish tint. This effect is present in almost all white diamonds, and finding one in which this is undetectable is extremely rare.

The colour scale ranges from 'D' (completely colourless) to 'Z' (tinted yellow). We do not use diamonds with tints below 'M' as they tend to look dull . The higher the colour the brighter the diamond and this is the part of your choice were your money is best spent. The first three colours 'D' 'E' 'F' are colourless and are recommended for the purist. Colours 'G' 'H' 'I' are near colourless . They are easily the colours we recommend for most clients. Colours 'J' 'K' 'L' 'M' show faint colour and are recommended for the budget conscious.

It is really pretty simple. The closer to 'D' you go, the more expensive the diamond. Can you see the difference between a 'D' colour and a 'K' colour? In fact the 'K' colour will look pretty dull in comparison to a D. However, if you look at 2 diamond rings from a distance, it becomes a lot more difficult to tell the difference between them. Most people will not be able to tell the difference between a ' D' and a 'G' colour when mounted. If you're the type of person who wants the absolute best, by all means purchase a 'D' colour; but don't be surprised if a lower colour grade looks just as good.

Coloured diamonds, known as ‘fancy diamonds’ are even rarer than perfectly colourless diamonds and extremely expensive. These colours include pink, yellow, blue, brown, orange, black and green.

Diamond characteristics– Clarity

Clarity is an indication of the purity of a diamond. When a rough stone is extracted from carbon, deep beneath the earth, tiny traces of natural elements, usually non-crystallised carbon, are almost always trapped inside. Further, there are often structural imperfections such as tiny cracks, which can appear whitish or cloudy. These imperfections are called inclusions. Most inclusions are not visible to the eye, so a jeweller will use a magnifier, known as a loupe, to reveal a diamond’s inclusions.

The number, size, colour, relative location and visibility of inclusions all affect the relative clarity of a diamond, and diamonds are increasingly rare and precious when they have higher clarity grading. Only around 20% of all diamonds mined have a clarity rating high enough for the diamond to be appropriate for use as a gemstone, while the other 80% are relegated to industrial use. Of the top 20 percent used in fine jewellery, a significant proportion contains one or more visible inclusions. Most inclusions found in gem-quality diamonds do not affect the diamonds' performance or structural integrity, but large clouds can affect a diamond's ability to transmit and scatter light.

Diamonds are graded by the major societies on a scale ranging from flawless to imperfect.

Links to other information pages


History and background of Diamonds
Diamond Shapes
Conflict Diamonds
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