metamorphic
Tiffany Stone
Bertrandite Fluorite (CaF2 + Be4Si2O7(OH)2)
Hardness: 4 to 7 (variable); Color: Purple, violet, white, cream, and black; Luster: Vitreous to dull; Crystal Structure: Amorphous blend/polyminerallic; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.5 to 3.0
- Hardness
- 4 to 7 (variable)
- Color
- Purple, violet, white, cream, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 4 to 7 (variable); Color: Purple, violet, white, cream, and black; Luster: Vitreous to dull; Crystal Structure: Amorphous blend/polyminerallic; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.5 to 3.0
Formation & geological history
Formed through the pneumatolytic alteration of limestone by fluorine-bearing fluids in a volcanic environment, specifically within the Spor Mountain beryllium deposits (c-6-40 million years ago/Cenozoic Era).
Uses & applications
Primarily used in jewelry (cabochons and beads) and for lapidary arts like carvings and spheres. Due to its beryllium content, it is also industrial ore for high-tech aerospace and defense manufacturing.
Geological facts
Also known as 'Opalized Fluorite' or 'Ice Cream Opal,' this rare material is found in only one location worldwide: the Brush Wellman Beryllium Mine in Topaz Mountain, Utah. It is a 'byproduct' gemstone of the mining process.
Field identification & locations
Identify by its distinctive purple and cream swirled movement. In the field, look for nodules of purple coloration within rhyolitic tuff. Collectors should seek pieces with high color contrast and minimal fractures.
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