Many people believe that diamonds are classified by size rather than by weight. The word size is often used instead of weight in public retailing: “How big is the diamond?” Size could consist of a measurement of diameter, as for example, 6.5 mm (millimeters) for a 1.00 carat diamond. Indeed, most semi-precious stones are sold by size, since their value does not warrant exact weight determination. For example, cubic zirconia, an inexpensive diamond imitation, is sold by size. A 6.5 mm CZ would weigh about 1.60 carats, since it is much heavier than diamond. But when dealing in diamonds, every point (1/100 carat) could be critical in determining the wholesale value.