What is a Carat?

This unit of weight for precious stones is equal to 200 milligrams. It is thought that the name carat was derived from the carob tree. Carob trees are native to the Old World (Asia, Africa, and Europe) and are known for their uniformly-sized seeds. Gemstones, including diamonds, were weighed for years against these seeds. A diamond weighing less than one carat would be measured in points. One hundred points equal one carat. A diamond weighing more than one carat would be listed as the whole carat number, plus the number of points. For example, a diamond that was one carat and 25 points would be listed as 1.25 carats.