Struggling to make next month's rent, you might be tempted to dig out some necklaces and rings you don't wear and try to sell it to your friendly neighborhood jeweler. But you might actually be buying a ticket to a sick magic show. The jeweler performs a blistering series of slight of hand tricks, whipping out calculators, spouting off fees, keeping your eye on the supposedly worthless diamonds under a tenth of a carat while double-deducting for the base metal. By the end, you slink out in a dizzied blur, accepting 1/5th of what the piece is actually worth. In this exclusive excerpt from the latest issue of Harper's, ex-jeweler Clancy Martin takes you on a journey to the dark underbelly of the jewelry game.