The 4 Cs

1. Carat refers to the weight of a diamond. There are five carats in one gram. A clear, colourless, perfectly cut diamond weighing 5 carats would be worth a staggering £420,000 at a conservative estimate, the price of a large family house! However, the same one gram weight consisting of five perfect one carat diamonds would cost a mere £40,000, or £8,000 each, so you could have fifty-two perfect one carat diamonds for the price of one 5 carat diamond. What is the better investment? The answer is of course the 5 carat diamond, because its value will increase at a faster rate than the 55 one carat stones, because it is much rarer, and it's easier to sell one diamond to a rich man than it is to sell 55 diamonds to 55 "poor" men.

To come back down to earth, this carat weight business is very important (as are the other 3 C's, of which more later). I often receive enquiries from people who want me to find them a nice one carat diamond. They have read somewhere that a nice G/VS2 diamond should cost around £2,000 per carat, so could I find them a one carat diamond for £2,000? The problem is that the £2,000 per carat was referring to a half carat diamond, which would indeed cost around £1,000. However, a one carat diamond would cost nearer £5,000, or five times as much.

2. Colour, or rather lack of colour, is the second C. Most diamonds have a slight yellowish or brownish tint, which is usually barely noticeable to the untrained eye. The less colour a diamond has, the more valuable it is (when taken in conjunction with the other 3 C's, I hasten to add!). Colour is represented by the letters of the alphabet. This is best illustrated with a table:

Letter	Colour Grading
D, E, F	colourless
G, H, I, J	near colourless
K, L, M	very slightly tinted yellow
N, O, P Q, R	faint yellow
S -Z	light yellow

If an M colour diamond is placed face down next to a D colour stone, the first diamond will look tinted, even to the naked eye. However, the M colour diamond, face up and on its own, will look almost colourless, especially if it's a smaller stone, say up to 5mm or half a carat. Since the price of a half carat  M/SI1 diamond would be about £400, as against £1,000 for a D/SI1, low colour stones represent excellent value for money, especially if the buyer prefers yellow gold for the setting.

3. Clarity refers to the number and type of inclusions present in a diamond. Crystals, feathers (minute cracks), clouds and twinning wisps are just a few of the types of inclusions which can be found under 10x examination. Small inclusions have little, if any, effect on the brilliance of a diamond, but they do considerably affect a diamond's value. If a diamond has many inclusions, or several large inclusions, the brilliance of the stone may be impaired; such diamonds are described as I2 or I3, or P2 or P3. A well-cut I1 or P1 diamond  can look as good or even better than a less well-cut VS or SI stone. The following table gives the various clarity grades at a glance:

4. The Cut of a diamond is perhaps the most importamt of the 4 Cs. The brilliance of a diamond depends very much on the amount of light that is reflected back to the eye, and the quality of the cut is all-important in this respect. There are many factors which determine the quality of a diamond's cut, but the two most important are the depth percentage and the table percentage. Crown angle and crown height are also very important. For a good illustration of the factors affecting diamond cut, visit this web page: How to Buy a Diamond