Here is a comparison of characteristics of Cubic zirconia to diamonds. They might look alike but they are completely different substances. Diamonds are made of the element Carbon (C). There is no carbon in a CZ. It is made of zirconium dioxide (ZrO2). The science teacher in me just loves this kind of stuff. Hope you are interested. Color: Since CZ are synthetic, they can be made absolutely colorless Diamonds usually have a yellow or brown tinge, the truly colorless diamonds are very rare. Definition: Cubic zirconia (or CZ), the cubic crystalline form of zirconium dioxide (ZrO2), is a mineral that is widely synthesized for use as a diamond simulant Diamond is a natural mineral, an allotrope of carbon. Crystal habit: CZ Dipyramidal prismatic Diamond ZIsometric, Octahedral Luster: CZ Adamantine Diamond Adamantine Material: CZ Synthetic Diamond Natural Hardness: CZ. Relatively hard. 8.5 on Mohs hardness scale Diamond Extremely hard (10 on Mohs scale). The hardest known natural material. Specific gravity: The specific gravity of CZ is between 5.6 to 6 and is relatively 1.7 times more than that of a diamond of the same size Diamond has a specific gravity of 3.52 Refractive Index: CZ 2.176 Diamond 2.417 Chemical formula: CZ ZrO2 Diamond C Dispersion: CZ. 0.060 (higher than diamond) Diamond 0.044 (lower than cubic zirconium and moissante) Density: CZ Between 5.5 and 5.9 Diamond 3.5 – 3.53 Thermal conductivity: CZ are thermal insulators Diamonds are among the most efficient thermal conductors Flaws: production of cubic zirconia is virtually flawless Diamonds definitely have some kind of flaw* Melting Point: CZ 2750 C (4976 F) Diamond 3550 C (6422 F) Cut: In CZ, the shape of the facet is sometimes different from that of a diamond