<human>: Is there a way to tell if an opal is a synthetic or natural?
<bot>: Yes, there are ways to determine whether an opal is natural or synthetic. Natural opals are formed through the precipitation of silica within a geologic matrix and can be identified by their distinct color patterns. Synthetic opals, on the other hand, are made up of glass beads that have been embedded in resin and then fired at high temperatures. These opals will usually have a milky-white color and may also have inclusions such as air bubbles or cracks.