For example, akoya pearls can only grow about 9 or 10 millimeters ... it has to be cut and polished. This is when the real value of the gem is determined. There's a huge demand for black opal ...

Japan's akoya oysters have been preëminent among cultured pearls ever since Kokichi Mikimoto first established the industry in the early part of this century. But since 1994, something has been ...