What Is Cubic Zirconia or CZ?

What Is Cubic Zirconia or CZ?

wolv/Getty Images

Cubic zirconia or CZ is the crystalline manmade form of zirconium dioxide, ZnO2. Zirconium dioxide is also known as zirconia. Ordinarily, zirconia would form monoclinic crystals. A stabilizer (yttrium oxide or calcium oxide) is added to cause zirconia to form cubic crystals, hence the name cubic zirconia.

Properties of Cubic Zirconia

The optical and other properties of CZ depend on the recipe used by the manufacturer, so there is some degree of variation between cubic zirconia stones. Cubic zirconia typically fluoresces yellowish green to gold under shortwave ultraviolet light.

Cubic Zirconia Versus Diamond

In general, CZ exhibits more fire than a diamond because it has a higher dispersion. However, it has a lower index of refraction (2.176) than that of diamond (2.417). Cubic zirconia is easily distinguished from diamond because the stones are essentially flawless, have a lower hardness (8 on the Mohs scale compared with 10 for diamond), and CZ is about 1.7 time more dense than diamond. Additionally, cubic zirconia is a thermal insulator, while diamond is an extremely efficient thermal conductor.

Colored Cubic Zirconia

The ordinarily clear crystal may be doped with rare earths to produce colored stones. Cerium yields yellow, orange and red gems. Chromium produces green CZ. Neodymium makes purple stones. Erbium is used for pink CZ. And titanium is added to make golden yellow stones.