In times past pearls were considered to be a sound investment such as gold or real estate. That’s because to find only one pearl thousands of oysters had to be searched. Today people take shell beads and place them inside an oyster, then place it back in the water to be harvested once the oyster has covered the bead with layers of nacre. It’s no longer a mystery which oyster is carrying a pearl, they all are!
Most cultured pearls are produced in Japan. The larger oysters of the South Pacific produce South Sea cultured pearls and Tahitian black cultured pearls that are larger in size. China produces freshwater pearls using mussels.
You judge the quality of a pearl by the orient (the soft iridescence caused by the refraction of light by the layers of nacre) and by luster (the surface reflectivity and shine). Shape, size and color also impact their value.
To tell the difference between an imitation pearl and a cultured and natural pearl rub it against the edge of a tooth. The cultured and natural pearl will feel slightly rough like fine grain sandpaper. Imitations will be smooth as glass.