Precious Stones like Diamonds and Gems are always measured in carat weight. One carat is the equivalent of 1/5 of a gram. Additionally, there are "100" points in a carat, so that a .50 "point" it would be described as a half-carat.

In general, the pricing structure for polished Precious Stones are directly related to the pricing structure for the Stones in their rough state. Because there is a scarcity of large Precious Stone rough, the price for these Precious Stones after polishing will be higher per carat. As you get larger in carat weight there will be an incremental jump in price even between two stones of same color and clarity. These plateaus are found approximately every .10-.15 points. Category examples are: .50-.59, .60-.69, .80-.89, .90-.99 carat, etc