New Acquisitions - Mexican Fire Opal
- Photography by Ken Larsen. Gift of Anton Rosenthal, 2008.
Fire opals are transparent to semi-transparent, resembling gelatin, with a red, orange, or yellow body color, with or without play-of-color. The body color is caused by inclusions of iron oxides. Gem opal consists of tiny silica spheres tightly packed together; the voids or spaces between the spheres contain air or water. The play-of-color in opal is due to the orderly arrangement of these spheres acting like a diffraction grating, breaking visible white light in to separate colors. Fire opals are commonly referred to as Mexican opals because most of the finest fire opals are found in Mexico. Opals are typically cut en cabochon or polished free-form to best show the play-of-colors. However, due to their transparency, many fire opals are faceted. This fire opal cabochon is semi-transparent with an orange body color and displays beautiful green, yellow, orange and red play-of-color. With magnification, looking inside the opal you can see interesting inclusions: "stalagmite and stalactite" formations that are probably goethite rods, along with what appear to be hematite crystal inclusions. This Mexican fire opal has all the characteristics of a unique and beautiful gemstone and is a wonderful addition to the National Gem Collection.
- An unusual tube growth formation with larger terminating crystals. Photography by Wimon Manorotkul, courtesy of palagems.com.
- Coral-like stalagmite/stalactite formations are clearly seen in this magnification. Photography by Wimon Manorotkul, courtesy of palagems.com.
- This single stalagmite formation is one of many found in this intriguing Mexican fire opal. Photography by Wimon Manorotkul, courtesy of palagems.com.
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