Opal doublets, often used in jewelry, are thin slices of precious opal glued onto a base material. Such gems are considerably cheaper than solid opals, yet .
Diatomaceous opal (an opal containing diatoms) is also called Fuller's earth and tripoli. This type of opal is used as a fine powder abrasive on metals, precious .
Because of that opal is best suited for use in earrings, brooches and other pieces of jewelry that rarely encounter scuffs and impacts. When used in a ring, the .
Opals used in jewelry fall into one of three categories: black opal, white opal and fire opal. Black opals have a dark background illuminated by iridescent flashes .