Diamonds of equal weight can vary greatly in price depending on a number of factors; the most important of which are referred to as the 4Cs: Carat, Cut, Colour and Clarity.

The 4Cs is an attempt to make objective comparisons between diamonds. In reality they are professional opinions - opinions which do vary. It is not easy to put concepts such as a stone’s brightness or scintillation into equations. The same diamond may well be graded differently in different countries with some favouring certain criteria over others.

Carat
Carat refers to the weight of the diamond. 1 carat = 0.2grams.

Known as 1 carat it also contains 100 points.

The name derives from the word Carob. Carob is a tree which has a fruit with a very consistent weight, which made for an ideal counter weight in ancient times.

Weight is the only one of the 4Cs that is actually objective. Diamond weight is extremely precise - so much so that what we are weighing is actually diamond mass.

The larger the diamond the rarer it is - for example a 1 carat diamond is more than double the price of a half carat diamond, all other factors being equal.

Weight is considered the most important factor in determining the price of a diamond.

Cut
A description of shape which also relates to the quality of craftsmanship in the finished diamond.

In the first instance cut refers to the shapes that you see, of which the round (known as ‘brilliant cut’) is the most recognised. Other popular shapes are square (princess), oval, pear shape and emerald (rectangular). Less well known cuts include Briolette, Ashoka and the context cut, to name but a few.

A well cut diamond will capture the maximum amount of light, break it up, spray it around within its structure and project a brilliant display of fire and colour that is so distinctively diamond. This most prized attribute should always be sought.

Colour
Diamonds have varying degrees of colour in them, more commonly yellow/brown. Colour grading charts the presence of colour from colourless to light yellow.

A perfect diamond crystal is absolutely colourless; however diamonds do come in every colour of the rainbow. The majority of diamonds mined and sold are variations of colourless diamonds, sometimes incorrectly referred to as white diamonds. This is incorrect because white is a colour and it is a lack of colour that we are looking for. Introduced by the Gemmological Institute of America in the 1930s, the current grading system replaced the use of other less detailed or misleading terms. It offers a simple grading system for colourless to light yellow diamonds.

Diamonds with a natural and distinctive colour are very rare. The most expensive colour is unquestionably red. Intense pink is also exceptionally rare as are blue, green, purple and yellow. Canary yellow is a vibrant gold colour unlike the duller yellow colours at the lower end of the colour scale.

Clarity
Diamonds have their own characteristics known as flaws and inclusions. Clarity grading attempts to put diamonds into categories depending on the visibility of these marks.

Of all the diamond grading processes this is the most difficult. The gemmologist must consider the nature of the inclusion; as well as the quantity, size, colour, location and visibility. Their only tool is a gemmological microscope or a hand-held magnifier called a loupe.