How do jewelry thieves know whether a pearl is valuable enough to be stolen?

There may be more than one way, but Arthur Barry, a great 1920 thief who has stolen half a million dollars a year, has a unique and fast technique. In the theft at the Plaza Hotel in 1925, Barry managed to escape the $ 750,000 jewelry. James P. Donahue, daughter of F.W. Woolworth. The theft was not only done during the day, but Barry secretly took the jewelry from the dressing table, while Mrs. Donahue soaked in the bathtub a few meters from the place. Among the stolen items there is a pearl of $ 450,000. However, jewelry drawers not only have one pearl, but five pearls, four are imitations. Is Barry's choice only good luck? Not at all, he carefully rubbed the pearl into his teeth. "Fake pearls are smooth and slick," he says, "but the original pearls give a slightly rough sensation, like a grille."

Source :