Diamonds & Other Stones


There are four main characteristics used to judge the quality and value of any individual diamond. These are known as the ‘four C’s’: Colour, Clarity, Cut and Carat. For any diamond, the better its relative ‘C’s’ the rarer it is and therefore the higher the value.

Colour for a ‘white’ diamond is a measure against a letter based comparative scale of how colourless or lacking in yellow tints it is. The scale starts at D for the whitest diamond and goes all the way to Z, dropping in value as stones show more hints of colour, until at the lower end of the scale values increase again when tints are intense enough to be considered a fancy colour such as canary yellow, intense pink and many others. Diane Hall, Creative Director of Dower & Hall, considers the colour of a diamond to be the most important quality. “The colour we use most is graded as ‘F’ or ‘rare white’ – which  is beautiful and bright and looks great in our platinum settings. An engagement ring is a once-in-a-lifetime purchase and you want it to be special, so you should always get the best colour you can afford. Most of the diamonds we sell are F, G or H, but of course if money is no object then nothing can compare to the exceptional whites of D or E.”

Clarity is the measure of the size, quantity and location of the tiny inclusions present in most diamonds – evidence of their natural origin. We prefer to use stones in which the inclusions are barely visible through a microscope because a diamond will only have true brilliance if the clarity is ‘VS’ (Very Slight inclusions) or better. ‘SI’ (Slight Inclusions) is a compromise but the inclusions are still not visible to the naked eye.

Cut is a description of the shape of the diamond with round being the most popular and many other fancy shapes available such as square princess, oval, marquise, and pear. Cut is also the measure of proportions, symmetry and polish, all of which can affect how much sparkle, life and fire a diamond displays. As a craftsman and qualified gemologist, Dan Dower considers the cut of a diamond to be the most important quality “because a well-cut smaller stone can have more presence than a poorly proportioned larger ‘rock’. The cut is the most difficult quality to measure, but when you are comparing and choosing stones individually, the life and sparkle of a beautifully crafted diamond is clearly discerned. Always choose quality over size!”

Carat is a measure of the weight of a diamond (not to be confused with the carat of gold which is a measure of purity). A modern carat is a fifth of a gram, and is often split into hundredths known as points - a 0.25ct diamond can also be called 25pts or a quarter carat. Larger diamonds are rarer so weight has an exponential effect on the value of a diamond - a full carat diamond is worth a lot more than two half carats.

All of our diamonds, 0.40 carat or larger, are Certified - this means that they have been independently assessed for quality and come with a certificate to prove it.

Conflict-free diamonds are those which have been obtained using legitimate methods. This means these stones have not been mined due to child labour, violence or abuse of human rights and precautions have been taken to ensure minimal damage to the environment.

We have built trusted relationships within the jewellery industry to ensure that the precious gemstones we supply in our designs have come from conflict-free sources.


We are often asked if an inherited diamond can be used in our designs. We are not opposed to doing so but each stone has to be judged for its suitability. We would prefer not to compromise our standards by using poor quality stones in our rings, however we have created some lovely pieces using antique stones ‘of character’ set in to a complimentary design.

If you are thinking of buying your own diamond (especially over the internet) then we would advise you to be cautious. Many stones are advertised and sold on the strength of the easily assessed and compared qualities of Colour and Clarity. The stone may look good on paper but its ‘life’ depends on the quality of its Cut and this is very subjective and harder to compare. We only ever sell stones of ‘very good’ or ‘excellent’ Cut to give maximum appeal and ensure your ring becomes a lifetime’s treasure.

We need to assess any proposed stone for flaws that could cause problems in the setting process and can result in damage - we will advise you accordingly. However we do not accept any of the risk in these scenarios. We also need to make sure that the size and shape of any diamond is suitable for the design that you would like to put it into. If the size or shape is different to one of our standard settings then we may need to create a new one for which there may be a fee.


Not all stones are suitable for use in a precious ring intended for every day wear, the main considerations are below, but please call 020 7377 5544 to discuss other stones in more detail.
HARDNESS – this is measured on the ‘Mohs’ scale from 1 to 10 – a comparable measure of a stone’s resistance to scratching.
Diamond at 10 is the hardest with Sapphire & Ruby next at 9 – these three precious stones are suitable for most purposes.
Most other crystal stones are 8 to 7 and may be scratched with heavy wear so we need to consider whether they are suitable for everyday wear.
Some stones are very soft so only suitable for occasional wear – for example Tanzanite at 6.
DURABILITY – this is a measure of how a stone resists breaking under force or a knock, as well as it’s resistance to chemical attack. Some stones are very durable with Diamond, Sapphire & Jade being good examples. Most stones are average and can be chipped or broken only with a sharp blow, whilst others such as Emerald are very prone to stress or cracking because of weak crystal structures.
If you have any further questions we can ask Dan Dower who is a fully qualified Gemmologist.

Go back Back to top
ACID logo