Pearls are an organic gem, created when an oyster covers a foreign object with striking layers of nacre. Long ago, pearls were significant financial assets, similar in price to real estate, as thousands of oysters had to be searched for only one pearl. They were rare because they were created only by chance.

Today pearls are cultured by man: shell beads are located inside an oyster and the oyster is returned to the water. When the pearls are later harvested, the oyster has enclosed the bead with layers of nacre. Most cultured pearls are produced in Japan. In the warmer waters of the South Pacific, larger oysters produce South Sea cultured pearls and Tahitian black cultured pearls, which are larger in size. Freshwater pearls are cultured in freshwater mussels, mostly in China.

The quality of pearls is judged by the orient, which is the soft iridescence caused by the refraction of light by the layers of nacre, and sheen, the reflectivity and shine of the surface. Fine pearls do not have any flaws or spots in the nacre: it has an even smooth texture. Other factors which affect worth are the regularity of the shape, size, and colour: rose tints are the most preferred.

Cultured pearls and natural pearls can be illustrious from imitation pearls by a very simple test. Take the pearl and rub it (gently!) against the edge of a tooth. Cultured and natural pearls will feel slightly rough, like fine sandpaper, because of the texture of natural nacre. Imitations will feel as smooth as glass because the surface is moulded or painted on a smooth bead.