Pearls are either natural, cultured or imitation. A natural pearl is formed when an irritant-often a piece of sand-gets into certain mollusks and is turned into a pearl by the fluid released by the mollusk. Cultured pearls are formed the same way, but the irritant is implanted deliberately by humans. Imitation pearls are usually glass or plastic beads covered in layers of a solution made of the scales of fish. Identifying an imitation pearl is vital to determining the value and quality of pearl jewelry.
Slide the pearls between your teeth. Fake pearls are smooth and will glide, while real pearls feel gritty as they slide. The layers of nacre (the material mollusks produce that coats the irritant) on the pearl create the feeling of grit.
Rub two pearls together. If they feel sandy or gritty as they are making contact, they are real.
Study the pearls until a magnifying glass or microscope. If the surface of the pearl looks grainy, it is an imitation. If you see a surface that looks like it is covered with scales or a maze, the pearls are genuine.
Drill a small hole in the pearl. A real pearl will have many layers of nacre and a clear delineation between the nucleus of the pearl and the nacre layers. An imitation pearl will have a much thinner outer layer.
Examine the pearls' flaws, shapes, luster, size and color. If the pearls look identical, they are most likely imitation. Real pearls have natural variations in these areas.