metamorphic
Tiffany Stone
Fluoritized Opal Beryllium Tuff (composed of Fluorite; CaF2, Opalized SiO2, Bertrandite, Chalcedony, and Quartz)
Hardness: 5-5.5 (Mohs scale), Color: Variegated levels of purple, lavender, white, cream, and black; Luster: Vitreous to waxy; Crystal structure: Amorphous; SG: 2.1-2.6
- Hardness
- 5-5
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Variegated levels of purple, lavender, white, cream, and black; Luster: Vitreous to waxy; Crystal structure: Amorphous; SG: 2.1-2.6
Formation & geological history
Formed through the hydrothermal alteration of volcanic ash (tuff) into fluorite. It is estimated to be approximately 6-10 million years old (Miocene-Pliocene epochs), associated with the Brush Wellman beryllium mine.
Uses & applications
Primary source of Beryllium for high-tech industry (aerospace, defense, x-rays); polished for use as semi-precious gemstones in jewelry and decorative carvings.
Geological facts
Also known as Bertrandite or Ice Cream Opal, it is exceptionally rare as it is found in only one location worldwide: the Topaz-Spohr Mountain area in Juab County, Utah. It is technically a mining byproduct.
Field identification & locations
Identify by its unique 'swirled' purple and white pattern and lack of transparency. Collectors should look for high-contrast purple veining. It is no longer legally available for public collecting at the original source mine.
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