A few quick tests you can perform to determine if a pearl is real or fake.
How can you tell the difference between real pearls and fake pearls? Here are several simple and easy tests almost anyone can use to determine if a pearl is real or fake.
An old wives tale says that if you hold a real pearl in your hand, it will be cool to the touch for several seconds before warming up. Resin or plastic pearls are often warm upon first contact; however, glass pearls may take longer to warm in your hand than real pearls — thus, it is important to remember the Touch Test is not a 100 percent reliable method for checking authenticity.
Rub a pearl lightly along the biting edge of your upper front teeth. If it feels slightly rough, sandy or gritty, it's likely a cultured or natural pearl. This texture you feel is the layers of nacre that have formed over time. If the pearl feels smooth or glassy, it is likely an imitation.
Hold the pearl up to the sunlight or very bright indoor lighting to check for variation's in a pearl's color and tone. If the pearl is perfect in color and tone, it is very likely fake.
Look at a pearl through an ordinary magnifying glass. You should be able to see the ridges and irregularities of a real pearl — or the grainy smoothness of a fake pearl.
A real pearl tends to be heavier than a fake pearl.
A real pearl is drilled as small as possible to maintain it's value; a fake pearl often has a much larger drill hole than a real pearl. The surface of a fake pearl will also often flake off around the drill hole.
A real pearl is a product of nature; therefor, it is produced with some degree of irregularity. If the pearl is a perfect sphere, it is likely a fake pearl. Real (cultured or natural) near perfectly round pearls are extremely rare and worth substantial amounts of money.