More fashion companies are launching collections of precious gems and metalsIn the consumer psyche, fine jewelry from the likes of Chanel, Louis Vuitton, and Christian Dior is no less evocative of the brand than its latest shoe or handbag. It’s easy to forget that the merger between fashion and fine ­jewelry is a relatively new phenomenon—Chanel and Dior, for instance, entered the haute joaillerie business in the aughties. And now—lured by the gleaming prospects of diamonds, precious metals, and gemstones—a slew of fashion companies have thrown their hats into the fine jewelry arena. For globally recognized fashion labels, the carrot is hard to resist: U.S. fine ­jewelry and watch sales are projected to have reached $66 billion–$68 billion in 2011, according to the Jewelry Research Institute. Globally, that number is estimated to be $135 billion–$140 billion. Additiona