Opal stone

   The opal is one of the main precious stones. It has been mined for thousands of years for use as a jewel. Long ago, people thought the opal had magic powers. Some thought it brought bad luck, but the Romans wore opals as good luck charms. At the present time, Hungary and Australia produce the best opals, but the stone can also be found in many other parts of the world.
   The common opal has a body color of milky white, pale yellow, or black. The better opals are iridescent, which means they show^ shifting lights of reds, yellows, blues, and greens. Opals are a variety of quartz. Their origins date back to prehistoric times when water, seeping through volcanic ash, dissolved the mineral silica and was then deposited in petrifying wood or rock cavities. The "opalescence" or iridescence of this gem, which is its source of beauty, is also its weakness. The lines of varying colors are actually fractures or lines of strain formed in its development. While these lines reflect light, they can also cause breakage in the stone. An opal cannot be cut into facets but must be polished into a rounded surface and carefully mounted.