The diamond has become a unique symbol of commitment; rare, precious, magical and indestructible; all these qualities have made diamonds the perfect symbol of true love and romance. But with so many different levels and grades of diamond out there, how do you ensure you understand what you are getting for your money?

The Four C's

Mark Walker, Creative Director of Icecool.co.uk a leading online jewellery store, explains that choosing the 'perfect diamond' is a very personal and very individual process. "You need to decide if you are into size or quality and buy the best that you can possibly afford. A larger diamond of medium quality will be the same sort of price as a smaller diamond of very good quality."

So how to choose between size and quality? What really matters? The quality and value of every diamond is evaluated using four key criteria (the four C's) – carat, clarity, colour and cut, and an understanding of these is important when making your diamond buying decision. Edward Johnson, Director of the Gemological Institute of America (GIA) in London, which grades and certifies diamonds, comments: "The four C's are really a system of communicating quality. In reality no one is more important than another, as they work in relation to each other. It is about matching expectation within the four C's. If budget comes in to play, something has to give."

Carat

The carat is the unit of weight for diamonds; A carat weighs 0.20 of a gram and is divided into 100 points, therefore a three-quarter carat diamond is 75 points, a half carat diamond is 50 points and a quarter carat diamond is 25 points and so on....

The bigger the stone, the greater the rarity and therefore the higher the price per carat. In fact only one in a million diamonds weigh more than a carat.

Clarity

Imperfections within the diamond can reduce the clarity grading and therefore the value. Known as 'inclusions' or 'clarity characteristics' as the GIA likes to call them, many are invisible to the naked eye and can appear under the microscope as black specks or small clouds.

Colour

To the untrained observer most diamonds will appear to have no tint colour, but most are slightly coloured and are evaluated on a scale from pure white to tints of brown. Johnson explains; "It's like putting a drop of yellow food colouring in a glass of water. The first few drops the water won't look any less white, but after a while you will start to notice the difference."

Pure white (exceptional white D) is rare but 'fancy' colours are extremely rare. The highest price paid per carat at auction for a diamond is US$1 million for a 0.95 carat red diamond.

Cut

The cut of the diamond is the final key to setting the value. The finest and most exact cutting (ideal cuts) and polishing will maximise the diamond's fire and lustre. For Johnson, this is one of the most important elements of the four C's.

"This is what the professionals look at and is what people should focus on as ultimately this is what makes the diamond have that unique sparkle." However he stresses that it really comes down to personal preference. "I would suggest a smaller stone of a higher clarity and a high cut grade, but some people want more 'flash for their cash' and so choose to compromise in other areas."

The fifth C – conflict diamonds

In recent years a '5 th C' has become increasingly important – 'Conflict Free'. With the film Blood Diamond raising the profile of the issue recently, a guarantee that diamonds have not originated from war-torn parts of the world is more essential than ever now.

In December 2000, a resolution was passed to found a certification scheme that would help stop the trade in illicit diamonds. In 2002 the Kimberley Process was put into place. It is obviously having a big impact. Whereas in the 1990s conflict diamonds constituted an estimated 15% of the international trade in rough diamonds, this figure is now estimated at a fraction of 1%.

This KP system is advocated by the World Diamond Council and the system of warranties that supports the KPCS means that all buyers and sellers of rough and polished diamonds must state a guarantee on all invoices to be audited and reconciled them annually. If your jeweller can state this on their invoices, you are guaranteed that the Kimberly Process has been followed throughout the supply chain. You will not get an individual certificate for your diamond.

Choosing the shape

So having chosen the type of diamond to suit your personal taste and budget, how do you then choose what shape to look for? Mark Walker of Ice Cool says, "The shape of the diamond you choose very much reflects your personality. Therefore consider your core characteristics and let the shape come from this. Round is seen as traditional and modest, oval more adventurous. Square is great for the more fashion-conscious, whereas heart shaped suits a real romantic. Pear is very confident, marquise stands out from the crowd and rectangular is perfect for lovers of retro."

What to do next

1) Firstly do your research – get educated about diamonds and their grading, using this article and more detailed information from the GIA website

2) Find a jeweller you can trust, either by recommendation or from the National Association of Goldsmiths, or the British Jewellers Association.

3) Set a budget – whether £100 or £1million, there is a diamond out there to suit everyone.

4) Make sure the diamond you buy has a grading report from an association such as the GIA. This will not only give you confidence about the four C's but also that what you are buying really is a diamond.

For information on Icecool's bespoke service 'You Dream We Create' service visit www.icecool.co.uk.

Coutts is sponsoring Coutts London Jewellery Week in 2008. Click here for further information.

Other useful links

Gemological Institute of America

Kimberly Process

British Jewellers Association

National Association of Goldsmiths