Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925.
Cubic zirconia (CZ) is the cubic crystalline form of zirconium dioxide. The synthesized material is hard and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirconium silicate. It is sometimes erroneously called cubic zirconium.