Diamonds are measured in what is called carat weight which stems from an old form of measurement involving carob beans. At one time, if a diamond weighed the same as a carob bean, it was considered one carob or one carat. Today, the measurements are a bit more precise and one carat is 200 milligrams.
You may also hear a diamonds weight referred to as grains which stems from another ancient form of measurement. In the far east, rice was used to measure the weight of a diamond. If the weight equaled 4 grains or rice it was called four grains – or one carat as we know it to be now.
You have to be leery when buying diamonds that are already set or mounted. If there is more than one diamond in the piece then the tag will show the CTW or Carat Total Weight which is the combined weight of all stones. It will not tell you the weight of each stone in the piece, therefore you must ask the jeweler for the total carat weight of the largest diamond in order to really know what you are buying.
Clarity
There are basically two things to think about when evaluating the clarity of a diamond - inclusions and blemishes. Inclusions are flaws inside the diamond and blemishes are those on the surface. Diamonds are graded by the amount of inclusions and blemishes and whether or not they can be seen by the naked eye.
Many diamond buyers mistakenly think that diamond clarity refers to how clear it is but this is not the case.
Clarity actually refers to the external as well as internal imperfections in the stone. The best diamonds, of course get a grade of FL or IF – Flawless or Internally Flawless – meaning that it is perfect. A grade of I-1, I-2 or I-3 means that the diamond is imperfect, with a grade of I-3 being the worst.
Cut
Contrary to what most people think, cut does not refer to the shape of the stone, but to the facets that are cut into each stone. These facets are critical as they are what causes the stone to reflect light and what gives it, it’s brilliance. Even the most wonderful diamond can be ruined if it is not cut properly.
Jewelers follow a mathematical formula to insure that a diamond is cut to show the maximum brilliance of the stone. As with anything cut affects price and there are several grades of cut to consider when buying a diamond.
The best cut is called “Ideal Cut" and it is perfectly per portioned to maximize the brilliance of the stone. The next best cut is called “Premium" which is also very desirable and is less expensive than the ideal cut. A “Very Good" cut is one step down from the premium but still reflects most of the light from the stone.
In some cases, the cutters vary the proportions of the cut to result in a larger diamond. The “Good" cut is an economical grade - lower than the “Very Good" but quite popular with most people buying diamonds as it still shows the stone off quite well. “Fair" and “Poor" cuts should be avoided as they do not result in a sparkly brilliant diamond. These diamonds are cut to specifically maximize size but they sacrifice brilliance in the process.
