How old are the Opals?
It has been found that Australian Opals are over 100 million years old. This period is called the "Placozoa" during the early Cretaceous period. As there was high volcanic activity and the planet was surrounded by silicon dioxide and water, which was the perfect combination for natural opals creation!
Opal is non-crystalline silica, similar to quartz, but is not a mineral. Its internal structure enables unique diffraction of light to produce white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Opal is formed from a solution of silica (very fine sand-like particles) and water. In some sandstone outback regions, water passes through the sandstone to form a silica-rich solution that flows to voids formed from decomposed fossils and as the water evaporates, a silica deposit is left. This is repeated over vast periods and from it, an Opal is formed.
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.
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