CZ

• Cubic zirconia (or CZ), is the cubic crystalline form of zirconium dioxide
• 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
• In the Middle Ages, zircons were believed to induce sleep, as well as promote honor and wisdom
• Zircon was believed to bring prosperity to its owner, moreover, zircon was thought to drive away plagues and evil spirits
• In addition to zirconium, silicon and oxygen, zircon contains small quantities of rare earths and radioactive elements such as thorium and uranium

PEARL

• A pearl is a hard, roundish object produced within the soft tissue (specifically the mantle) of a living shelled mollusk
• A pearl is made up of calcium carbonate in minute crystalline form, which is deposited in concentric layers 
• The ideal pearl is perfectly round and smooth
• Pearls from the sea are valued more highly than freshwater pearls
• A "natural pearl" is one that forms without any human intervention at all, in the wild, and is very rare
• Many hundreds of pearl oysters or pearl mussels have to be gathered and opened, and thus killed, in order to find even one wild pearl
• A cultured pearl, on the other hand, is one that has been formed on a pearl farm
• The thinner and more numerous the layers in the pearl, the finer the luster 
• The thinner and more numerous the layers in the pearl, the finer the luster
• Cultured pearls can be distinguished from natural pearls by X-ray examination. A cultured pearl shows a solid center with no concentric growth rings, whereas a natural pearl shows a series of concentric growth rings
• Pearls come in eight basic shapes: round, semi-round, button, drop, pear, oval, baroque, and circled