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Expert Advice

We love sharing what we know, so here’s some
information we think you’ll find useful.

How to assess diamond quality

Buying a diamond is something most people do very rarely, but it’s usually a considerable and exciting investment, so let us give you some pointers on the main factors determining the cost and value of a diamond.

The most important things they are looking for are often known as the 4 Cs: Carat, Cut, Clarity and Colour.

Before you buy a diamond, there are a number of things you can do to make sure that you are roughly able to assess the quality of the diamond yourself. Although it takes years to become a real expert, if you read up and educate yourself before you go shopping, you are far less likely to pay too much for your diamond engagement ring.

A simple jewellers’ loupe, a 10x magnification lens, is widely available and our advice is that you should buy one before you go shopping. It’s a very small investment, but a jewellers’ loupe will help you check that you are happy with the cut of the diamond, possible inclusions, the colour etc. It gives you added peace of mind when you buy your diamond engagement ring.

Carats are the units of weight used for diamonds. Each carat is divided into 100 points. 1 Carat equals 1/5 gram. Remember that a carat is weight, not size and that a well-cut diamond may appear larger than a badly cut diamond of equal weight.

Colour is also graded, in this case from D to Z. A diamond graded as D will be colourless, the most desirable and the most expensive. However, the difference between it and a stone graded E is not noticeable to the non-expert and even an expert needs a comparison stone to see the difference. Once a diamond is mounted on a yellow gold ring, for example, it is generally almost impossible to tell the minute colour grade differences.

At the bottom end of the scale a Z diamond would be noticeably yellow, but these are not used in jewellery and Vashi.com sells nothing below I.

Very occasionally diamonds are found with a natural colour to them, the most famous probably being the blue Hope Diamond, today housed in the Smithsonian Museum, which started life as The French Blue when it belonged to the King of France. These stones command huge premiums but natural coloured diamonds are available in all shapes and sizes.

Cut is where the skill of the diamond cutter creates the maximum shine and sparkle from the rough stone. For many centuries the priority was to get the largest possible gem that could be cut from the rough. Nowadays, whilst still hoping not to waste precious material, the cutter is more likely to go for maximum brilliance. This is achieved by cutting the diamond so that light entering it is reflected back to the beholder.

The better the cut the more light reflected. A well cut diamond is worth far more than a badly cut stone of equal weight. Shape is also an aspect of cut with the most fashionable shapes, currently round and square, commanding a premium over less fashionable ones.

Clarity denotes the number of flaws in a diamond. These are formed as the diamond is being created in liquid magma inside the Earth. Internal flaws are known as inclusions, external ones as blemishes. A jeweller will look for flaws with a loupe. He will note every flaw and grade the stone accordingly.

One other element which can affect the value of a diamond is fluorescence, which is the way a diamond “soaks up” light. Diamonds are graded None to Strong for fluorescence, with those with a high level considered less desirable and thus cheaper.

Most of the above aspects of diamonds you will be able to assess at a basic level with some education and the help of a jewellers’ loupe. Of course you should always be free to take your diamond to a reputable jeweller to be assessed by an expert.