Cubic Zirconia or CZ is is the cubic crystalline form of zirconium dioxide (ZrO2). The synthesized material is hard, optically flawless 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 (ZrSiO4). Because of its low cost, durability, and close visual likeness to diamond, synthetic cubic zirconia has remained the most gemologically and economically important competitor for diamonds since 1976.
Rhinestone or paste or diamante on the other hand, is a diamond simulant typically made from glass. Glass is silicon dioxide, also known as silica (from the Latin silex), is an oxide of silicon with a chemical formula of SiO2. The availability of glass rhinestones was greatly increased when around 1775 the Alsatian jeweler Georg Friedrich Strass had the idea to imitate diamonds by coating the lower side of glass with metal powder. Hence, rhinestones are called Strass in many European languages. Crystal rhinestones are produced mainly in Austria by Swarovski and in the Czech Republic by Preciosa and a few other glassworks in northern Bohemia. In the US, these are sometimes called Austrian Crystal.
I have been using CZ and rhinestones in my Bridal jewelry for many years now. Both are very attractive and provide diamond like sparkle. The CZ I currently work with is by far one of the best stimulants that I have used, primarily due to the incredible faceting of the stones.
(References: http://en.wikipedia.org)
