Diamonds & the 4 C's

            ​Diamonds & the 4 C's


Buying a Diamond Ring to some may come quite easy and straightforward, however to most it is like buying a Wedding outfit or a new Car, sounds simple right, till it comes to the moment of choosing, then your mind goes blank, followed by panick, as truth dawns that it is actually so easy to get it all wrong. This page will hopefully ease alot of this for you, as once you get an idea of what is in a diamond(s), and what exactly is it you want from them, the rest should be plain sailing.


Weight (Size) of a Diamond  :  Carat

Carat, one of the 4C's (carat, colour, clarity, cut), is the unit of measurement used to describe the weight of a diamond. The word carat originated from the carob tree - the tiny seeds of this tree are well known for their uniformity and consistent weight. Traditionally, diamonds and gemstones were weighed against these seeds until the system was standardized, and 1-carat was fixed at 0.2 grams. 1-carat is divided into 100 points, just as 1 pound is equal to 100 pennies. A diamond weighing one quarter of a carat can also be described as weighing 25 points or 0.25 carats or 1/4-carat. Points are generally not used to describe weights over 1 carat.





Scarcity of Larger-Size Diamonds

Diamonds are formed between 75-120 miles beneath the earth's crust and may take thousands of years to surface where they can be mined. Most diamonds were actually formed billions of years ago. So while all diamonds are rare, the larger stones (1 ct or larger) are even scarcer. So, generally speaking, larger diamonds have a greater value per carat. This is why a diamond's carat size has the biggest impact on the price of the diamond.

Weighing the Diamond

Gemological laboratories usually measure the carat weight before the diamond is mounted, or when it is loose. In jewellery pieces that have more than one diamond, the carats are usually expressed in terms of the total carat weight. This weight is the combination of all the diamonds in the particular piece.

Size Versus Weight

People in the jewellery industry may use the terms size and weight interchangeably, although they are both different. Size refers to physical measurements in millimeters while weight refers to carat size. The variety of proportions in a diamond will yield stones that have the same carat weight but are different in size. When a diamond is cut well they tend to appear smaller in size. This is in contrast to a diamond that has been "spread" to cause the consumer to believe that the stone is larger than it really is. When considering purchasing a diamond, it is important to really understand both size and weight in terms of what appeals to your taste and budget.

Carat Affect on Cost

When considering the price of a diamond, you should think in terms of per-carat cost. In order to calculate the cost of a diamond, use the following equation:

carat weight times per carat cost = total cost of the diamond.

For example, a 1.50 carat diamond say VS2 I colour and clarity GIA certified starts at and costs £6,000 per carat would be 1.50 (carat weight) times £6,000 (per carat cost) or £9,000. Most stores and websites state the total cost of a diamond but understanding the per carat cost can help you better compare different diamonds.

To calculate the diamond's per-carat cost, divide the total cost of the diamond by the weight. For example, if a diamond costs £1,500 and the weight is 0.75 carats, the per carat price is £1,500 divided by 0.75 carats or £2,000, Usually, the greater the weight of the diamond - the more rare it is and the greater the price. Expect to pay a premium for diamonds that are above 1.00 carat in weight. For example, a 0.95 carat diamond will cost slightly more than a .90 carat diamond. A 1 carat diamond will cost considerably more than a 0.90 carat diamond


Cut (Shape)

A common misunderstanding is that the term ‘diamond cut’ would also refer to the diamond’s shape. However, cut is what determines how well-cut your diamond is, whereas shape is the shape it was cut into. Diamonds can be cut into various shapes of which the round brilliant is probably the best known.




Most diamonds range in colour from white to slightly yellow. However, diamonds can occur in all sorts of colours ranging from brownish to striking yellow, pink, purple, red and blue. These are called ‘fancy colours’.





All diamonds have traces of their growth history. The clarity scale reflects the size, number, location and visibility of the internal characteristics when examined with a 10x loupe.