Gem quality opal from Australia. SEM Image of the opal. Compare near-gem quality opal and gem-quality fire opal x magnification) from (dry) Lake Tecopa, Inyo County, California, USA; SEM images courtesy of Ma Chi
Peridotite is a coarse-grained intrusive igneous rock that is composed almost entirely of olivine. It may contain small amounts of amphibole, feldspar, quartz or pyroxene. The specimen shown above is about two inches (five centimeters) across.
Ethiopian opal is still a new gemstone. Ethiopian opal is quite unique and different from more common Australian and Mexican opal. Not many people know about this opal yet. I am a gem cutter and have worked.