A 1 carat diamond used to equal the weight of a carob seed, but in today’s terms
the carat is a standard metric weight of weight of 0.2 grams or 1/142 of a standard
ounce. Each carat is divided into 100 points. So, for example, a quarter of a carat
is 25 points, written as 0.25; a half a carat is 50 points, written as 0.50, and
so on. It is easy to weigh unmounted diamond, but once it is in a setting, it is
only possible to estimate its weight by using special gauges and formulae.