How do I tell if pearls are real?

As a keen observer of the intricate world of finance and cryptocurrency, I often find myself wondering about the authenticity of things, much like when assessing the genuineness of digital currencies. Now, imagine I'm standing in front of a jewelry counter, admiring a string of pearls, and I turn to you, the expert, and ask: "How do I tell if these pearls are real? I've heard about so many ways to test them, but I'm not sure which ones are reliable. Should I look for a certain luster? Or try the tooth test? And what about the weight? Does a real pearl feel heavier or lighter than a fake one? With so many fakes out there, I want to be sure I'm investing in something genuine.