Maria Doulton: Not to be forgotten is another vital 'C', and that is of course carat.
Carat refers to the weight of the stone, and
one carat is one fifth of a gram.
Now, you don't need me to tell you that a large diamond is more valuable than a small diamond, but it is interesting to know that large diamonds are of course rarer, so this means that
a 5.00 carat diamond is many times more valuable than a 1.00 carat diamond;
it isn't simply five times more valuable.