Carat, the name of an imaginary weight by which diamonds are rated; and also a term used for expressing the fineness or purity of gold. The alloy is supposed to be divided into 24 parts called carats, and its fineness is reckoned according to the number of these which are pure gold. Gold 20 carats fine is 20 parts of pure gold alloyed with 4 of some other metal. The term has been so long in use that its origin is very obscure. Some suppose it to be derived from the Greek , a fruit corresponding to the Latin siliqua; whence the Arab word Tcyrat, a weight, imaginary part, or share. Bruce says of a bean he met with in a famous gold mart of Africa: "The fruit of the tree called leuara is .a red bean which seems to have been in the earliest ages used for a weight of gold. This bean is called carat." As usually employed by jewellers, the weight of a carat is 4 imaginary grains, of which 74 1/16 are required to counterbalance 72 grains troy.