In its natural state, the jaw-dropping gem known as emerald often resembles an ancient barrel-shaped decree from a king. It tells us things nothing else can. Today, the glittering green stone stops an onlooker. It takes our breath away. When set against a backdrop of shimmering gold, it is something that transfixes us. The calming color of an emerald actually gives the eyes a rest after working for a while. In fact, some think looking at emeralds relieves eye strain, a spark...