When choosing diamond jewellery, the first thing most people consider is the carat; but what is a carat and what’s important? Well, despite the heading of this article, a carat is not directly a measure of size… but it is closely related!
[image:By Mario Sarto (Self-photographed)]
It was once thought that the size and weight of the Carob seed was the most uniform of all seeds and thus was used as a way of measuring and valuing jewels during ancient times. This was in fact wrong; the carob seed is no more uniform than many other seeds, however the name stuck and evolved to what we now call a carat – a measure of weight of gemstones.
Today, 1 carat is 200 milligrams, and although we often mistakenly refer to a diamond’s carat as its size, there is of course a direct relationship between its weight and size – a 2 carat diamond is going to look larger than a 1 carat diamond of a similar cut but it will not be double in size as some might imagine!
A brilliant cut diamond must meet an exact standard, so you can in fact quite accurately estimate its carat weight by measuring its diameter:
You will notice in the chart though that a 4 carat brilliant cut diamond does not look twice the size of the 2 carat one, this is because as the diameter increases, the bit you see (the crown) increases too, but a lot of the expansion occurs in the base of the diamond, known as the pavilion.
What carat to choose
The first thing to consider is cost. Larger stones are rare and so command a price premium (less than 1 in a million rough diamonds mined can be cut into a stone of over 1 carat). The price premium grows quite exponentially with higher carats (and of course colour, cut and clarity have an effect). Under 1 carat, there is a large choice and you will find the price increase from, say, 0.5 carat to 0.6 carat is not too much. However, over 1 carat the price rises rapidly with size; a 3 carat stone will cost a lot more than three times the price of a 1 carat stone of similar colour and clarity. In fact, you may pay ten times as much for a 3 carat than a 1 carat stone.
For earrings, the diamonds are seen from more of a distance than when showing-off a solitaire ring, so it is better to go for more carats and compromise on the clarity and colour a little. For a solitaire engagement ring though, which is going to be viewed much closer, even inspected, then colour and clarity and the quality of the cut will be more noticeable so it may be worth reducing the carat a little to get a better quality stone. A clever trick for adding volume is to choose a Halo style setting. A Halo surrounds your main diamond with smaller diamonds - adding impact and of course extra sparkle!
For those in the know
TOP TIP! Most people look for a diamond with a carat weight in multiples of a quarter (0.25, 0.50, 0.75, 1.0 etc.). Because of this demand if you buy a diamond which is slightly different, such as 0.45 or 0.9 carat for example you are likely to pay a little less on a price-per-carat basis.
Remember though, the price of a diamond is based on its colour, clarity and cut as well as its carat weight.