The
carat (
ct) is a
unit of
mass equal to 200
mg (0.2
g; 0.007055
oz) and is used for measuring
gemstones and
pearls. The current definition, sometimes known as the
metric carat, was adopted in 1907 at the Fourth
General Conference on Weights and Measures, and soon afterwards in many countries around the world. The carat is divisible into one hundred
points of two milligrams each. Other subdivisions, and slightly different mass values, have been used in the past in different locations.