Cz is the short form for Cublic Zirconia. Cz are used in children's jewellery as an alternative to crystals, some of which contain lead. Most manufacturers no longer use leaded crystals in children's jewellery but cz do not contain lead. Their resemblence to diamonds makes them a popular form of sparke in children's earrings and bracelets. Wikapedia says "Cubic zirconia (CZ) 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." The colours are almost limitless. Pink cz is regularly used in baby jewellery but it's common to find amethyst, ruby, garnet, sapphire and more colours in cz. Cz are very durable and make an economical competitor for diamonds since commercial production began in 1976.