The term "carat" is a measurement of weight. Not to be confused with Karat, which refers to the purity of gold. Carat is just as often confused with size, even though it is solely a measurement of weight. One carat is equivalent to 200 milligrams. Five carats equals one gram. In essence, one carat is equal to 1/5 of a gram (or 0.2 grams). Also, bear in mind that different gemstones are made up of different chemical elements, therefore they do not all weigh the same.
The point unit is equal to one one-hundredth of a carat (0.01 carat, or 2 milligrams) is commonly used for diamonds of less than one carat. All else being equal, the value of a diamond increases exponentially in relation to carat weight, since larger diamonds are both rarer and more desirable for use as gemstones.
Total Carat Weight (T.C.W.) is a phrase used to describe the total mass of diamonds or other gemstones in a piece of jewelry, when more than one gemstone is used.
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