Cubic Zirconia (or CZ) is zirconium oxide (ZrO2), a mineral that is exceptionally rare in nature but is broadly synthesized for use as a diamond simulant. The synthesized material is hard, optically flawless and usually colourless, but may be made in an assortment of different colours. It should not be confused with Zircon, which is a zirconium silicate (ZrSiO4).
Because of its low price, durability, and close visual similarity to diamond, synthetic Cubic Zirconia has remained the most geologically and economically significant diamond simulant since 1976. Its main competition as a synthetic gemstone is the more lately cultivated material Moissanite.