Cubic zirconia is a far less expensive man-made stone that resembles diamonds in appearance, but they are not the same. Cubic zirconia is a zirconium dioxide-based man-made mineral. CZs resemble diamonds in appearance, but their mineral structures are significantly different. Small quantities of cubic zirconia have been discovered in nature, but the great majority of the zirconias used in jewelry are man-made in a lab. Synthetic diamonds are manufactured in laboratories as well, however they have the same carbon structure as diamonds, but cubic zirconia does not.