Carat is the measurement used to weigh a diamond. One carat is two hundred milligrams. The smallest diamonds can measure .005 of a carat, but normally the smallest are .01 ct. The size of the diamond greatly reflects on the price. The difference between a diamond that is .99 ct and a 1.00 ct diamond is about a thousand dollars or more depending on the color, cut, and clarity per carat. Diamond pricing is also measured by carat, for example a 2 carat diamond that is $10,000 per carat would cost $20,000. Diamonds are very rare and big diamonds are extremely rare. Keep us in mind when you want to buy or sell diamonds in the Dallas area.