Semi-Precious Gemstones: Tiffany Stone
Opalized Fluorite used in Jewelry
Source: Utah, USA
Tiffany Stone (aka opalized fluorite, opal fluorite, opalite, bertrandite (beryllium silicate), or ice cream opal) with its dramatic display of bold colors, jagged shapes, and black veins looks like some sort of abstract-expressionist painting by Jackson Pollock. Tiffany Stone is a rare and unusual "opalized" (agatized) mineraloid that formed in mineralized nodules called "beryllium nodules."
Tiffany Stone is composed of varying combinations of minerals such as bertrandite (beryllium silicate), beryl, calcite, chalcedony, cobalt, dolomite, fluorite, manganese oxide, rhodonite, quartz and zinc. The purple color that characterizes Tiffany Stone was created by fluorine gases, while the distinct black-colored veins were caused by manganese oxide; all of which were sealed within the sedimentary layers, becoming opalized over time. Unlike precious opal, Tiffany Stone does not display any opalescence or "play of color" that is common in its namesake.
Opalized fluorite is a mineraloid which is a combination of amorphous hydrated, fluorine-rich mineralized fluids and silica-rich sediments. Amorphous materials where naturally created by the rapidly cooling molten material, and the rapid cooling process slowed and suspended the material's molecules before they could pack into a tight crystalline structure. The opalized fluorite formed in Irregular veins and nodules which were originally clasts of carbonate rock, incorporated into the beryllium tuff during eruption .
The rareness of Tiffany Stone comes from the fact that to date, the only location it has been found is at the Brush Wellman beryllium mine in the Topaz-Spor Mountains of Juab County's Sevier Desert, in western Utah. Beryllium (Be) is a light-weight, high-strength yet brittle alkaline earth metal which is used in structural materials for aircraft, missiles, communication satellites and space vehicles. Adding to the scarcity is the fact that the extraction process for beryllium involved crushing large quantities of material which yield only 1 to 2 percent of the concentrated ore. This remote mine is now closed to the public, as the beryllium dust generated in the extraction process is highly toxic.
Tiffany Stone (Opalized Fluorite) Properties
| Crystal System
|| amorphous, mineraloid |
| Crystal Habit
|| nodules |
| Specific gravity (SG)
|| 3.18 |
| Mohs Hardness Scale
|| soft |
| Surface Luster
|| vitreous, resinous, waxy |
|| fair to good |
|| conchoidal |
|| subtranslucent to opaque |
| Gem Color
|| blue, brown, mauve, grey, tan, purple, reddish-brown, black|
| Chemical Composition
|| CaF2 (fluoride)|
Due to its softness and total opacity, Tiffany stone opalized fluorite is always cut and shaped into a cabochon. Due to the toxicity of any trace amounts of beryllium, a respirator must be used when cutting Tiffany Stone.
A similarly exotic material called "Candy Stripe Opal" (aka bacon opal for its resemblance to a side of bacon) is also found in western Utah, in the Thomas Mountain Range near the city of Milford in Beaver County. Candy Stripe Opal is slightly translucent material which has striated bands of pink red, white and yellow.
Bibliography and Reference on Tiffany Stone (Opalized Fluorite)
1. Brush Wellman Beryllium Plant . www.brushwellman.com
2. Opalized Fluorite . www.skyesgems.com
3. About Tiffany Stone . www.utahlavender.com