Carat << KAR uht >> is a measure used by jewelers in weighing precious stones. The term is derived from the Arabic carat, meaning a bean or seed. In ancient times, the seeds of coral and carob trees were used as weights for precious stones. The stones were described to be of so many “beans’ weight” or “carats.” The metric carat weighs 200 milligrams, or 0.2 gram. It equals 3.086 troy grains, or 0.00705 avoirdupois ounce.
The term is also used to express the amount of gold in an alloy. In this sense, the word is spelled karat in most Western countries except the United Kingdom. A karat is 1/24 of the total weight of the alloy. For example, an 18-karat gold ring has 18 parts gold and 6 parts alloy. Pure gold is 24 karats.
