Weight measurement used in measuring the dimensions of a gemstone. A carat is 0.2 grams, or 200 milligrams. (The carat weight system can be used worldwide, even in the United States in which the system that is metric is not used.) A place is really a weight measurement used only by very small, precious gemstones such as Diamonds, and represents 1/100th of the carat.
The abbreviation for carat is ct. The term carat ought maybe not to be confused with karat which can be used to measure Gold quality