metamorphic
Tiffany Stone
Bertrandite-Bearing Fluorite Hyalite Opal
Hardness: 6-7 (Mohs scale); Color: Purple, lavender, white, cream, and brown; Luster: Vitreous to waxy; Crystal structure: Amorphous/Microcrystalline; Specific gravity: 2.1-2.9
- Hardness
- 6-7 (Mohs scale)
- Color
- Purple, lavender, white, cream, and brown
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Purple, lavender, white, cream, and brown; Luster: Vitreous to waxy; Crystal structure: Amorphous/Microcrystalline; Specific gravity: 2.1-2.9
Formation & geological history
Formed through hydrothermal replacement of volcanic rhyolite and limestone near beryllium-rich deposits. These specimens occur as nodules in volcanic tuff across the western United States.
Uses & applications
Used primarily in lapidary work for cabochons and jewelry. It is also an ore for beryllium, which is essential for aerospace, telecommunications, and high-tech defense industries.
Geological facts
This stone is found in only one location in the world: the Brush Wellman beryllium mine at Topaz-Spor Mountain in Utah. It is often called 'Ice Cream Opal' or 'Opalized Fluorite'.
Field identification & locations
Identified by its distinctive purple and cream swirl patterns. It is no longer legally open to the public for collecting, as it is a byproduct of active commercial beryllium mining.
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