So what makes an Opal precious? What are Opal made up of? Well at the basic level the Opal is a precious stone that is comprised of silica dioxide and varying amounts of water. Where it differs to other precious stones is that the opal does not form crystals but is made up of tiny balls of silica arranged in a regular pattern.
Where are Opals primarily found?
Opals are found in the following areas: The major areas in Australia for opal deposits are Andamooka, Coober Pedy, Lightning Ridge, Mintabie and Queensland. In the Americas, opal is found in Brazil, Honduras, Indonesia, Mexico and the western United States.
The Theory of Opal Creation
Most scientists believe that opal deposits were formed through a sedimentary process, when water-soluble silica in inland oceans created a gel-like substance that filled in crevices in the ground. Over time, the water evaporated from the gel, leaving the silica structure intact. They estimate that it takes 5 million years to make a layer of opal that is one centimeter thick.
Growing OpalAustralian scientist Len Cram has been able to grow natural opal at a much faster rate, one centimeter in three months. His observations from the experiments he has run have shown that opal deposits may initially form very quickly through a process called induration, and that these deposits then release their water much more slowly than traditional theory predicts.
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