Australia opal consists of decorative items worn as adornment, such as brooches, rings, necklaces, earrings, and bracelets. For many centuries metal, often combined with precious stones [I call them pretty stones], was the normal material for jewelry, but other materials such as shells. Think of dried plant seeds and even animal bones or even bird feathers. Precious stones [pretty stones] and similar materials such as amber, coral, precious metals, beads and shells were used. One of my favorites, Enamel, was often important.