Of the Four C's, carat weight is the easiest to measure and understand. One carat equals one-fifth of one gram and is divided into 100 points. So when you discuss a 3/4 carat stone, you could say it weighs .75 carat, or 75 points. To recover a single, gem-quality diamond, over 250 tons of ore must be processed. Of these diamonds, only one in 1,800 will weigh a carat or more. The scarcity of diamonds creates part of their value; the staggering rarity of large diamonds dramatically increases their value. Thus, a two-carat diamond will be more than double the price of a one carat diamond.