A complete example of the rare opal-replacement of a fossil bivalve shell, from the famous underground mines at Coober Pedy in Australia. Often, these simply go to the jewelry market as cutting rough, or to make pendants and such out of. It is getting harder and harder to find specimens like this. It shows a good play of color on the surface, when you pass light over it, and a nice bright white background to see the color against. Better in person as the opalescence is difficult to capture.
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