White opal forms over extremely long periods, sometimes taking as long as 5 to 6 million years to develop. They form from a solution of silicon dioxide and water. As water runs down through the earth, it picks up silica from sandstone and carries this silica-rich solution into cracks and voids caused by natural faults or decomposing fossils. As the water evaporates, it leaves behind a silica deposit. Over time, these deposits accumulate layer upon layer, solidify, and form what we see as opal.
Moreover, the specific play-of-color seen in white opals is due to the interference and diffraction of light by the regular array of silica spheres within the opal’s internal structure. The size of these spheres and their geometric packing determines the colors observed, ranging from violet through red; smaller spheres typically create blue and green colors, while larger spheres produce red and orange. This magical interplay of light and mineral structure is unique to opals, making them stand out among other precious gemstones.
