Octoberâ€™s birthstone is Opal. Precious opal is a gemstone that exhibits flashes of rainbow-like colors when viewed from different angles. The colors are created by an arrangement of silica spheres within the opal. The opals we see most often in jewelry have a milky-white base with varying flashes of color.
Do not use harsh cleansers on your opals and do not clean opals with ultrasonic cleaners. Never rub oil on an opal, because although it makes the fire brighter it can damage the opal. Some jewelers recommend you periodically soak opals in water to help them reabsorb lost moisture.