Some of the enchanting beauty of pearls come from their uniqueness: no two pearls are alike. Nature rarely replicates its creations; pearls are seldom perfect and identical. In other words, if a strand of pearls present with no imperfections it is likely an imitation. To further investigate:

Tooth test: although not sanitary, lightly rub pearls against the biting edge of your upper teeth. Real pearls will feel gritty and sandy whereas imitation pearls are likely to feel smooth.

Flaw test: if pearls appear flawless, they may be an imitation. Freshwater pearls are rarely perfect, hence their unique beauty.

Heaviness test: bounce the pearls in the cup of your hand. Unless the imitations pearls have solid glass beads, imitation pearls feel lighter than natural pearls.

Matching test: look at the virtues of pearls described above. Imitations are often perfectly matched.