The weight of [b]diamonds[/b] is measured in terms of carats. Infact carat is the unit for weight of all the gemstones. Larger the diamond more the value of it. A large diamond of 2 carats is of higher value then 2 diamonds of 1 carat each. One carat is equal to 100 points. So if a diamond is having 50 points means it is equal to 1/2 carat. Gram is equal to 5 carats.
The word carat is coined from carob seed which are small and consistent in weight. Carab seeds were used for measuring diamond weight in India in ancient times where the [b]diamonds[/b] were first discovered and traded. In modern times too the carat is nearly equivalent to one carab bean