Opal is thought by many to be one of the loveliest of the gemstones. The most commonly recognized is probably the white opal, but there are also black opals, fire opals, milk opals, boulder opals, and others. Polymer clay can cleverly emulate many natural materials, and luckily for us, opal is one of them. So even if you hold with the old superstition that it's bad luck to wear opals, you can still have a reasonable facsimile of this beautifully fiery gemstone with the help of a little polymer clay.