Carat Weight: The Fourth C in Diamond Education

The mass or weight of a precious diamond is measured in units called carats. One carat is exactly 200 milligrams. The term "carat" hails from the seeds of a carob tree, which are known to be uniform in size and consistent in weight. The traditional method of measuring the weight of gemstones and diamonds before the 20th century involved the use of these seeds as counterweight. However, with standardization of measurement, one carat unit was pegged at one-fifth of a gram, or 200 milligrams.

Raw or rough diamonds look nothing like the ones you see on jewelry display showcases. After a process of cutting and polishing, the final product will only weigh as much as two-thirds less than its original weight. Moreover, larger-sized diamonds of great quality are scarcer than smaller-sized stones of the same quality. You can expect the price of a larger-sized diamond to command a much higher price per carat in comparison to a smaller-sized diamond with exactly the same attributes.

In the United States alone, stones that weigh one carat and below comprise the total number of loose diamond pieces sold. Furthermore, the average American shops for a diamond engagement ring weighting half a carat or less.