CaratA diamond's size is measured in carat weight. (Big rock equals many carats). Each diamond carat is also equal to 100 points. For example, a diamond that is a 1/2 carat can also be referred to as a 50-point diamond. But keep this in mind : bigger isn't necessarily better. A two-carat diamond that is cut poorly is not nearly as beautiful as a smaller diamond, cut by a skilled diamond artisan. Or, it may be cut well, but have poor color and clarity. The point is, to be exceptionally beautiful, a diamond must be of high quality in all 4Cs.Clarity
A diamond's clarity is determined by the number, nature, position, size and colour of internal characteristics called "inclusions" and surface features called "blemishes". These irregularities occured in the liquid magna (volcanic rock) within which the diamond was created. Diamonds are mostly pure carbon, however, during crystallization other minerals nearby, or even other bits of carbon forming more quickly may have become trapped within the cooling mass. These show themselves as the various characteristics which make up the clarity of a diamond (included crystals, feathers, clouds etc). Clarity is measured on a scale ranging from pure (flawless) to heavily included (I-3). The clarity of a diamond is graded by using 10X magnification under good lighting by an experienced grader. The final clarity grade is usually determined by how easy the inclusions and blemishes are for the grader to see.
Ideally, a diamond should have no colour at all, like a drop of spring water. Increasing degrees of body colour are measured on a scale ranging from no colour at all (D) to deeply coloured (Z). Beyond "Z" is the range where the diamond's colour is vivid and rich, called "fancy colours". Diamonds of known colour are used as comparison stones for colour grading. Grading is done by comparing the diamond to be graded against these "master stones" under either artificial or natural north daylight ( in the Northern Hemisphere). A machine called the "Colorimeter" can be used for colour grading but there is no substitute for the trained human eye.
Cut, sometimes the forgotten "C", ensures that a given stone has maximum brilliance and sparkle which would not be the case were the stone cut for weight alone.
We use the following scale to grade a stone on it's overall appearance. The proportion page shows angles and percentages for round brilliant cut diamonds; but angles and percentages are for diamond cutters and graders. Simply put, when looking at a diamond, if it doesn't catch your eye or if it doesn't flash in the light, it's probably not well cut. Good cutting is what brings fire to the ice.
CertificationAlthough many diamonds look the same, not all of them are going to be of the quality you might like. Diamond certification is the written proof of a diamond's attributes. Without it, you have no assurance that the diamond you are buying is of the quality you're paying for. With it, you know the precise grading for each of the 4Cs – carat weight, cut, color and clarity – and, therefore, the diamond value.Diamond certificates are issued by independent gemological laboratories. There are several grading laboratories, the most prominent being: the International Gemological Institute (IGI) ; the Gemological Institute of America (GIA); the American Gem Society (AGS); the European Gemological Laboratories (EGL) and GemEx Systems.