Carat

Carat is a measure of weight. One carat (1ct) equals 0.20 grams and is divided into 100 points, so a half-carat (0.50 carat) diamond is also known as a 50 points diamond. No diamond is valued by carat weight alone – two diamonds of equal carat weight may have very different values depending on cut, clarity and colour. A diamond can appear larger or smaller than its weight, depending on cut. Your diamond may have a higher carat weight than a bigger-looking diamond with a shallower cut. Different designs and mountings also affect the appearance of size. 

Market perception of diamond weights, such as half-carat, one carat, or three carats, places an increased value on the weight categories.  For instance, a 1.01 carat diamond and a diamond of 0.96 carats will have a marked difference in value, though their cut, colour and clarity may be the same. Their difference is imperceptible side by side, but as they are valued on either side of the one carat boundary, the 1.01 carat diamond will be substantially higher in value.  As diamonds increase in size, they become increasingly rare in nature. As rarity is an important component of value, a one-carat diamond will be worth a great deal more than two 50 point diamonds of equal colour, clarity and cut.