Gemstones are commonly described and traded by carat weight in the gemstone trade but weight can be a deceptive measure of a gemstone's size and value. I believe that there are three reasons for this deception:

• Different gemstones have different densities. For example, a ruby and an emerald will possess a different amount of material mass within an equal amount of space. Simply stated, an emerald will weigh less than a ruby of equal size.



• Even for gems of the same kind, the attributes of weight and size are not the same. Cut, shape, and mounting can make two gems of the same weight appear to be of very different size.



• Weight and size are only two elements of a gem's beauty and value. Relatively large gems that lack the favorable qualities of color and clarity are commonly found. And they are commonly sold for far more than they are really worth to unsuspecting buyers.