That's because an untreated stone of the same quality is rarer and therefore more valuable. Jewelers should tell you whether the diamond you're considering has been laser-drilled. Imitation diamonds , such as cubic zirconia, resemble diamonds in appearance but are much less costly. Ask your jeweler if he has the current testing equipment to distinguish between diamonds and other lab-created stones. Pearls Natural or real pearls are made by oysters and other mollusks.
Imitation pearls are man-made with glass, plastic, or organic materials.
Because natural pearls are very rare, most pearls used in jewelry are either cultured or imitation pearls. Cultured pearls, because they are made by oysters or mollusks, usually are more expensive than imitation pearls. A cultured pearl's value is largely based on its size, usually stated in millimeters, and the quality of its nacre coating, which gives it luster. Jewelers should tell you if the pearls are cultured or imitation. Jewelers should tell you whether the colored pearls are naturally colored, dyed or irradiated.