The Australian Opal: Nature’s Eye Candy

October’s birthstone, opals are technically a mineraloid, rather than a full fledged mineral. They are comprised mainly of silica with a small percentage of water, and they form slowly over millions of years as layers upon layers of silica deposit uniformly in one spot. Not all opals that are formed will have the “play of light” or “opalescence” that we’ve come to signify with the opal’s name, but those that do can vary drastically in color simply based on where it’s formed and under what climate conditions. Opals can come in many colors, including black and green, and typically display almost every color of the rainbow in their opalescence.