One of the most simple and reliable ways of telling whether a pearl is real or imitation is by rubbing it gently across the front of your teeth. Real pearls will feel gritty. Fake pearls will feel smooth.
The reason for this is that real pearls are made of many layers of microscopic crystals of calcium carbonate that a mollusc builds up around an irritant. These tiny crystals reflect and refract the light that penetrates their layers, creating the glow from within that characterizes real pearls. Fake pearls feel smooth like glass or plastic because they are just manmade beads that have been coated with a shiny varnish or other material, sometimes incorporating iridescent fish scales to imitate the look of pearls.
Terms that refer to real pearls:
Natural pearls, Cultured pearls, Freshwater pearls, Akoya pearls, South Sea pearls, Tahitian pearls
Terms that refer to fake pearls:
Faux pearls, artificial pearls, man-made pearls, imitation pearls, Mallorca pearls, Majorica pearls
Other signs of fake pearls:
Fake pearls often look identical and perfect. Genuine pearls are all unique, like snowflakes. So each will have microscopic differences, and natural imperfections, which can be seen under magnification. Imitation pearls can all be the same “perfect” shape with no color variation or any imperfections because they are mass produced. A strand of genuine pearls will be made from individual pearls grown in different oysters and each pearl will be unique. So there will always be slight variations in size and sometimes in coloration and shape when looked at under magnification.
Fake pearls are sometimes lightweight according to what they’re made of. Real pearls are quite heavy.
Real pearls can feel cool to the touch, but after wearing them for a while absorb the warmth of the body.
The drill hole of fake pearls can sometimes show chips where the coating has come away from the bead.