Opal - October birthstone
If your birthday falls in October, your birthstone is the opal. This milky iridescent gem is symbolic of happiness, truth, and hope. The stone gets its name from opalus, the Latin word for "seeing jewel." The word might also come from the ancient Sanskrit word upala, meaning stone. In addition to being used as gemstones, opals are also used as ceramic ingredients, insulation materials, fillers, and abrasives. As gemstones, opals are given for the 14th and 18th wedding anniversaries.
Since ancient Roman times, opal has been highly prized as a jewel and precious stone. The Romans saw opal as a noble gem only the emerald was deemed more valuable. The Holy Roman Emperor's crown was topped by an opal, and opals also had a prominent place in France's crown jewels. Most of the opals of Roman times were mined from present-day Slovakia.
Opals are actually a solidified jelly rather than a crystal. Most stones are 60 million years old. They contain 13% water in some cases and small imperfections in the stones cause the opal's distinctive opalescence. In fact, opals in their pure state are colorless, but it is very rare to find opal with no impurities. In most cases, opals are milky with some base colors that depend on the materials that are in the stone. Opals containing iron oxides have red or yellow hues while opals with manganese oxides or organic carbon have black hues. White in opals comes from tiny gas-filled holes in the stones.
When selecting opals, keep in mind that vivid red stones are the rarest and most prized, so these will be the most expensive to buy. Black, dark blue, and gray opals are also very rare and fetch a very high price. White opal with pale colors usually is the most common and the most affordable. Fire opal is also a fairly affordable variety. Fire opals have a reddish, orange, or yellow color.
Since opals contain water and are not minerals, they tend to be more delicate than other gemstones. They require a little extra care to look their best. If opals dry out or are exposed to sun, they can lose their glow and opalescence. Ideally, opals should be oiled regularly to preserve their moisture. They should also never be exposed to harsh detergents. Stones should be protected from pressure as well, since opals are brittle and can crack or break.
When buying opals, you will find that most stones are either facet cut or finished en cabochon. Both cuts feature smooth surfaces that allow the stone to reflect light. Most stones are oiled or protected by water until they are sold. Some opals – especially the lighter varieties – are dyed to bring out vivid hues. If you are paying more for a deeply colored opal get verification that the stone was not dyed before you pay. Before buying your opal, you may want to get laboratory verification and speak to an informed jeweler. In addition to dyed opals, synthetic and imitation opals are sometimes sold as the real thing. When buying the stone, be sure to inspect it carefully for damage.