Carat (mass) Despite its being a non-metric unit, a number of metric countries have used this unit for its limited range of application. The Board of Trade carat was divisible into four "diamond grains", but measurements were typically made in multiples of carat. There were also two varieties of "refiners' carats" once used in the United Kingdom — the pound carat and the ounce carat. The pound troy was divisible into 24 "pound carats" of 240 grains troy each; the pound carat was divisible into four "pound grains" of 60 grains troy each; and the pound grain was divisible into four "pound
Gold coin example, a gold ingot identified as being .999 fine will be 999/1000 pure gold, with the other 1/1000 being impurities. Karat weight (K or kt) is a traditional fraction-based system used to denote the fineness of gold, with one karat being equal to 1/24 part of pure gold in an alloy. With the precision of modern assaying techniques, however, the fineness of gold ingots and bullion is more likely to appear as a decimal measurement. In this system, pure gold would be denoted as 1.000 fine. However, since absolutely pure gold is very soft and therefore not suitable for coinage